Depth of field and sensor size

We often address the question of, if we move from a camera with a certain sensor size to, for example, what happens to the depth of field.

Before I address that, I call attention to the fact that depth of field is not a property that is dictated by the laws of optics alone. If we have some hypothetical camera, with a lens of certain focal length and f-number, the camera focused at a certain distance, there is no unique optical situation at the two planes in "object space" we say are the limits of the depth of field. (No rays cross there, for example, nor is the image magnification for objects there equal to pi and pi minus one, or any such thing.)

Rather, the concept is one of our interpretation of a continuously-varying optical phenomenon: the rendering of a point on an object as a "blur figure" (called a circle of confusion) in the image if the object is not precisely at the distance at which the camera is focused.

The concept of depth of field is that blurring from imperfect focus that is less than a certain amount is "negligible", or "acceptable", and thus the range of distances to an object such that the blurring does not exceed that certain amount is considered the "depth of field".

To determine the depth of field by calculation, or even by observation, we must articulate our criterion of how much blurring is "acceptable" We normally do that by stating a maximum acceptable diameter of the circle of confusion (which I call the circle of confusion diameter limit, or COCDL).


How do we choose the COCDL value to adopt? A traditional way is this. Imagine the image is printed on a print of some arbitrary size, and we view it from some arbitrary distance. We then consider the circles of confusion as they appear on the print. We then say that the blurring is only "noticeable" (that is, not "acceptable") if the diameter of the circle of confusion on the print subtends a greater angle at the eye than the eye's resolution. Then maybe we double that just to make our criterion a little less stringent.

But this only pertains to a certain contrived viewing situation. Is there any generalizable form of that outlook?

Yes. It turns out that if we go through the math (or the maths, if we are in Great Britain), it suggests a certain COCDL as a fraction of the image size (we usually work in terms of its diagonal size).

And in fact the traditional COCDL number used by lens manufacturers is determined on that basis. But keep in mind that it is still as arbitrary as "the best age for a girlfriend is half your age plus ten years") - it doesn't flow from any principles of optics.

So now back to the question, "as we move from a camera with one format size to that with a large sensor size, what happens to the depth of field. Well, that question of course is not meaningful unless we resort to that old notion of "all other things being equal". And of course there again we have to make some arbitrary decisions.

One set of "all other things being equal" that can be useful is this:

• The focal lengths of the lenses will produce the same field of view on each camera.
• The cameras are focused at the same distance.
• The f-numbers of the lenses are the same
• The COCDL we adopt is a consistent fraction of the frame's diagonal dimension.

Then:

The depth of field of the larger-format camera is less than that of the smaller-format camera.

Now suppose that for some reason (hopefully relating to a special interest), we adopt this set of "all other things":

• The focal lengths of the lenses are the same.
• The cameras are focused at the same distance.
• The f-numbers of the lenses are the same
• The COCDL we adopt is a consistent fraction of the frame's diagonal dimension.

Then:

The depth of field of the larger-format camera is greater than that of the smaller-format camera.

Some people suggest that the most useful criterion of "blurring from imperfect focus being negligible" is when that blurring cannot be noticed at all given the resolution of the camera, but that is hard to define. Based on the same notion, they then suggest that perhaps we should consider the blurring from misfocus negligible if the diameter of the circle of confusion can just be resolved by the resolution of the camera. And so forth.

Any of these criteria will result in our adopting a COCDL that is related to the reciprocal of the camera resolution.

Sometimes the geometric resolution (based only on pixel pix) is used as a simpler predicate. The, we would choose a COCDL that was equal to some number of pixel pitches.How many? Well, that's a matter of judgment, like "how many months' salary should we try to keep in the bank".

Now, following that notion, let's again do our smaller and larger format camera comparison, for cameras with the same resolution in terms of picture height (or the same format height in terms of pixels, if we want the simpler criterion). That then suggests the same set of "other things being equal" we had at the beginning:

• The focal lengths of the lenses will produce the same field of view on each camera.
• The cameras are focused at the same distance.
• The f-numbers of the lenses are the same
• The COCDL we adopt is a consistent fraction of the frame's diagonal dimension.

Then, as before:

The depth of field of the larger-format camera is less than that of the smaller-format camera.

Another interesting case under this outlook is where the two cameras have the same pixel pitch. Then, the terms of comparison become:

• The focal lengths of the lenses will produce the same field of view on each camera.
• The cameras are focused at the same distance.
• The f-numbers of the lenses are the same
• The COCDL we adopt is the same.

Then:

The depth of field of the larger-format camera is less than that of the smaller-format camera, and to a greater degree than in the previous case.

***********

In part 2 of this series (after breakfast), I'll talk about what simple models will allow us to intuitively grasp these relationships. (Plot spoiler: not really any.)

Best regards,

Doug

Part 2

The following note deserves and would benefit from some illustrations. I didn't take the time to prepare such before I committed to do the note, so there are none. Sorry. I hope to reissue it with illustrations soon.

***********

The relationships I spoke of in part 1 flow from the equations for depth of field. But many people would like some intuitive insight into the source of these relationships, not dependent on the equations.

Sadly, such are hard to come by. But we can get intuitive insight into some pieces of the puzzle.

We start by recognizing that with the camera focused perfectly on an object point, rays from that point that enter the camera at different places across the lens' entrance pupil, and thus exit from different places across the lens' exit pupil, converge at a single point on the sensor.

These rays are all confined in a cone, whose base is the exit pupil and whose "height" is fairly close to the focal length (if focus is not at a close distance). Thus the cone angle is approximately related to the f-number of the lens (which we can think of as the ratio of the focal length to the pupil diameter).

For an object nearer the camera than the distance at which the camera is focused, that point of convergence would fall behind the sensor. The practical impact is that the rays of the cone, not yet converged when they strike the sensor, form a circular figure on the sensor (a circle of confusion).

For an object farther from the camera that the distance at which it is focused, that point of convergence falls in front of the. After the rays have converged, as we go further back in space, they diverge again, also forming a circular figure on the sensor.

The depth of field will be the range of object distances from where we have a blur figure in the first case with the diameter we adopt as our criterion of "acceptable blurring" to where we have a blur figure in the second case with that diameter.

We can easily visualize the approximate amount the point of convergence would differ between those two cases. But the corresponding location object follows a non-linear relationship with the location of the point of convergence, so we can not well visualize how much the difference in object distance would be.

Let's no look at changing some things.

• Increase the f-number (while keeping focal length, and everything else, constant). The diameter of the pupil decreases, and with it the diameter of the base of the bounding cone. Thus the cone angle becomes smaller. Then a greater departure of the point of convergence from the sensor plane (behind it or in front of it) is needed for the circle of confusion to grow as large as the limit we place on it. That greater departure of the point of convergence corresponds to a greater difference in the object distance. Thus the depth of field has increased.

• Increase the COCDL we have adopted. For any given cone angle, the point of convergence must now be further displaced from the sensor plane for the diameter of the circle of confusion to reach this new, larger, bogey. That greater departure of the point of convergence corresponds to a greater difference in the object distance. Thus the depth of field has increased.

• Increase the focal length (but keep the same f-number). Since we do not change the f-number, the angle of the cone stays the same. The departure of the point of convergence from the sensor plane needed to produce a circle of confusion of our limiting diameter is the same. But the relationship between the position of the point of convergence and the distance to the object depends on the focal length. (This is not easily visualized.) With a greater focal length, for a given difference in the location of the point of convergence, the difference in distance to the object is less. Thus the depth of field has decreased. This is not easily visualized.

• Increase the distance at which the camera is focused. As in the case above, the departures of the point of convergence from the sensor plane to produce the just-acceptable circle of confusion diameter is unchanged. But the relationship between the position of the point of convergence and the distance to the object depends on the distance at which the camera is focused. (This is not easily visualized.) With a greater focal length, for a given difference in the location of the point of convergence, the difference in distance to the object is greater. Thus the depth of field has increased.

Now, when we do something that changes two or of those parameters, the overall result is not easily visualized in any "intuitive geometric" way.

We can say that in some cases, the change in depth of field roughly linearly with the change in the parameter, while in other cases it varies roughly as the square, or the inverse square, of the parameter. Thus we can play a game of "what trumps what" to arrive at the relationships I discussed in the first part of that series. I will not do that here.

Best regards,

Doug

Part 3

In discussing some related issues with Will Thompson, he called attention to a discussion with a colleague who stated that, with regard to the increase in depth of field ("all other things being equal", not mentioned of course) when going to a smaller-format camera from a larger-format camera, this is principally traceable to the smaller distance from the lens to the sensor.

That seems to be true, based on observation. And in fact that distance is a parameter of the angle of the "cone", which of course fits into the story.

But as we follow the story to "object space", where the impact on object distance (the terms in which we express depth of field), we find that it is focal length that is really of interest.

Indeed, the focal length is generally close to the distance from the lens to the sensor.


And since, in a smaller-sensor camera, the focal length is typically smaller than in a larger-sensor camera (to get comparable field of view), then the distance from the lens to the sensor will also be smaller. But this is an artifact of focal length.

There is no intuitive model that flows directly from the distance from the lens to the sensor.

We can of course rewrite the equations for depth of field to use these inputs:

• The focal length of the lens.
• The distance from the second principal point of the lens to the sensor.
• The f-number.
• Our choice of COCDL.

or

• The distance at which the camera is focused (defined to the first principal point).
• The distance from the second principal point of the lens to the sensor.
• The f-number.
• Our choice of COCDL.

or

• The distance at which the camera is focused (defined to the first principal point).
• The distance from the second principal point of the lens to the sensor.
• The diameter of the pupil (in mm, for example)
• Our choice of COCDL.

or

• The distance at which the camera is focused (defined to the focal plane, as is commonly done).
• The distance from the first principal point to the second (the so-called hiatus distance)
• The distance from the second principal point of the lens to the sensor.
• The diameter of the pupil (in mm, for example)
• Our choice of COCDL.

and many other combinations.

In any case, I think it is not really helpful to say that, in the comparison between cameras of differing sensor size, the depth of field differs because of the different distance from the lens to the sensor.

Best regards,

Doug

Part 4

This is further to the matter of the difference in depth of field exhibited ("all other things being equal") on cameras of different sensor size being traceable principally to the difference in distance from (the second principal point of) the lens to the sensor.

Suppose we wanted to check this out with this model:

• Cameras of two different sensor size
• Focal lengths producing equal field of view *
• Cameras focused at the same distance *
• Same f-number
• Same distance from the second principal point of the lens to the sensor *
• COCDL the same fraction of sensor diagonal size

for which we would calculate the depth of field for the two cameras. We should expect to find it nearly the same.

Well, we can't do that at all. Why? Because that set of conditions is impossible. In particular, the properties marked with an asterisk cannot all be so.

This is a good clue that the assertion cannot be valid.

Best regards,

Doug

What does this really mean in practice? For example, what is the difference between a small format (24x36) and a medium format (6x7) if we want to keep the same perspective and framing and considering that we can get considerably faster lenses in small format (f/1.4 or even less) than in medium format (typically f/3.5)?

Hi, Jerome,

Jerome Marot said:

What does this really mean in practice? For example, what is the difference between a small format (24x36) and a medium format (6x7) if we want to keep the same perspective and framing and considering that we can get considerably faster lenses in small format (f/1.4 or even less) than in medium format (typically f/3.5)?

Click to expand...

First note that perspective is only determined from where we shoot from. So to keep the same perspective, we must start with the assumption that we will shoot from the same place.

That having been said, to keep the same framing we need to have the focal length be proportional to the frame size. Of course, 24 x 36 mm is not the same aspect ratio as 56 x 67 mm, so we never can have the same framing. But let's go on the basis of the frame diagonal. The 6 X 7 frame here is almost exactly twice the size of the full-frame 35-mm (FF 35). Thus if we use a 50 mm lens on the FF 35, we would need to use a 100 mm lens on the 6 x 7.

Now we can consider depth of field. I will assume we use the basis that the COCDL we will use is a fixed fraction of the frame diagonal size (lets say 1/1400). That would be a COCDL of about 0.031 mm for the FF 35, and about 0.062 for the 6 x 7.

Next we will assume an f-number for the full-frame 35-mm setup of f2.0, and a subject at 20 m. Then the depth of field would be about 26 m.

If on the 6 x 7 we also used an f/2 lens (100 mm), the depth of field would be about 10.5 m.

To attain the 26 m DoF we had on the ff 35 setup, we would need to use an f-number of about f/4.


So this actually plays out well considering the lenses that are available (at least at any reasonable price).

Best regards,

Doug

In order to give every advantage to the proponents of the "depth of field flows from the distance from the lens to the sensor" outlook, I have tried to contrive an intuitive model that flows from that.

Attempt 1:

With a shorter lens-to-sensor distance, a certain offset of the point of convergence from the sensor plane results in a smaller circle of confusion. Thus a larger offset will be needed to produce the "limiting" circle of confusion diameter. That larger offset translates to a larger offset of the object distance from the distance of focus at the acceptable misfocus limit, and thus constitutes a greater depth of field.

Doesn't that sound credible?

Nope. The first sentence is incorrect. For a given f-number, the angle of the bounding cone is the same. Thus, regardless of the distance from the lens to the sensor, a certain displacement of the point of convergence produces a the same size circle of confusion.

Attempt 2:

With a shorter lens-to-sensor distance, the offset in the point of convergence from the sensor that produces the largest "acceptable" circle of confusion is a larger fraction of the lens-sensor distance. That translates to an offset between the object distance and the object distance at ideal focus that is a larger fraction of the focus distance, and is thus just larger. That would constitute a greater depth of field.

Doesn't that sound credible?

Nope. The second sentence isn't true.

If we call the the location of the point of convergence (behind the lens) Q, and the corresponding object distance P, then:

dP = dQ*(-(P/f)^2)

where dP is the offset in object distance (from the distance at which the camera is focused), dQ is the offset in the location of the point of convergence (from the sensor plane), and f is the focal length. The distance to the sensor (that is, Q with no offset) is Q0.

Note that Q0 does not figure into the relationship at all.

Two flops! I'm gonna quit while I'm ahead.

Maybe there is no intuitive story that illustrates the notion that the greater depth of field in a smaller-sensor cameras flows from the smaller lens-sensor distance. Indeed there isn't, because that notion is just not so.


So, again, what does the greater DoF of the smaller sensor camera flow from?

• The shorter focal length we would use to get the same field of view (and this indeed affects the lens-sensor distance for focus at a certain distance, but does not come from a choice of that).

• The smaller COCDL we would adopt because of the smaller image size.

Best regards,

Doug

Doug Kerr said:

Next we will assume an f-number for the full-frame 35-mm setup of f2.0, and a subject at 20 m. Then the depth of field would be about 26 m.

If on the 6 x 7 we also used an f/2 lens (100 mm), the depth of field would be about 10.5 m

Click to expand...

This is correct, but it isn't the answer to my question. I realize I did not ask it in an understandable manner.

The question is "what does this mean in practice?". We can only take pictures with the cameras we have. Yet, sometimes, we want a given depth of field (small or large). Can we get what we want with the cameras that exist, considering what lenses are available for a given format? For example, you are talking about a f/2 100mm lens for 6x7 above, while no such lens ever existed for that format.

So, let me rephrase the question and split it in parts.

The question is linked to what lenses are available. Obviously, we can get the typical depth of field of a 24x36 50mm at f/8.0 and 3m distance in any format.

First: thin depth of field.
We can get thin depth of field in 24x36 (full frame) by using fixed focal lenses opened at typically f/1.4, sometimes more. These apertures exist at 21mm (Leica only), 24, 35, 50, and 85mm. Above that we can only find f/2.0 lenses. What happens in other formats (smaller or larger) with the lenses which are available? There is a f/0.95 25mm lens available for half frame. For 4.5x6, lenses max out at f/1.8. The Leica S system maxes out at f/2.5. For 6x6, lenses max out at f/2.0 (Hasselblad and Rollei) or more commonly f/2.8. For 6x7, one lens is f/2.8 (Mamiya RZ), but they typically max out at f/3.5.

The question is different if we want the convenience of zoom lenses. Zooms max out at f/2.8 (Olympus has a f/2.0 lens) for interchangeable lens cameras. Obviously, we cannot get a depth of field as thin with a half frame sensor than with a full frame sensor (for the same picture) since their zooms also max out at f/2.8. But if we use, say, a 18-50 f/2.8 lens on a half frame sensor, to what aperture does it correspond on a full frame sensor? What possibilities do we lose? What happens with the very small sensors used in P&S at long focal lengths (since it is the only possibility to limit depth of field with those cameras)? These cameras have large zoom ranges, but the aperture at the long end usually go down (and then diffraction limits resolution...).

Second: large depth of field.
This is typically only a problem in macro or close ups. For 24x36, we are usually limited by diffraction which degrades resolution above f/16 or f/11 with high resolution sensors. We can use smaller sensors with smaller focal lengths at a larger aperture (your typical digital P&S is usually a quite efficient macro machine), but up to which resolution? Very small digital sensors have minuscule pixels and the limits of diffraction appear sooner (as early as f/2.8 usually). Keep in mind that the approximation used in some formulas do not always apply when the distance between the object and the lens is similar to the distance between the sensor and the lens.

So off to Sikandria I went. My briefcase full of papers.
I knocked on the door. After a while a kindly looking man with a white beard
opened the door.

I kissed him on the forehead. Khalid's friend?, he asked. Yes, I said.

Come in and tell me what bothers you, said the gentle old man.

I showed him all my papers, all the files, the references. While he was studying the papers I had given, an even gentler looking lady came in with Arabic coffee and dates in a tray. I stood up. Kissed her immediately on her forehead.

She indicated for me to sit down with her eyes. Smiled at her husband and left.

After sometime ,while I had poured coffee for him and myself, Khalid's grandfather
stood up. He went to an old cupboard. I could see it was full of cameras and lenses.
Old. Must be worth a lot, I thought silently.

He brought me a box, opened it, took a lens out and put it in front of me.



Here he said. Look at it. See where it says 1.4,2.8,..5.6,8,11 etc. at the bottom.
Says the same on both sides of the 1.4 mark. Correct? I looked and said yes.

Look how 5.6 has a line connecting it to the row above marked ' m' for meters.
on the right it is about 10 meters. On the left it is about 2.8 meters.

Well son, he said what it means is that if you set the aperture on this lens ( fl=35mm ) and use it on a film M camera then: anything between about 2.8 meters and about 10 meters shall be in focus.

That's simple, I said. Khalid's grandfather told me it would work for all other apertures too! Just read the numbers, he said. But the circles of confusion, I interjected. ' Of confusion ' said the old man and
winked.

But, I said, I don't have a lens that has these markings.
He wrote me the name of a High Priest in Cairo and a High Priestess who could refer me to an Oracle.
As many Oracles as I wanted to talk too.

Sir, I said as I was leaving and had thanked him for his help; I am sorry but I did not ask your name.

That's alright son, he smiled. I am Fahim and this is my wife Ayesha.

fahim mohammed said:

But, I said, I don't have a lens that has these markings.

Click to expand...

Maybe, maybe not. Amongst Nikon, Canon, Pentax, Sony and Olympus, which of them still manufacture AF lenses with these markings today?

fahim mohammed said:

Just read the numbers, he said. But the circles of confusion, I interjected. ' Of confusion ' said the old man and
winked.

But, I said, I don't have a lens that has these markings.
He wrote me the name of a High Priest in Cairo and a High Priestess who could refer me to an Oracle.
As many Oracles as I wanted to talk too.

Click to expand...

Hi Fahim,

The old man was right. The markings on lenses are based on a IMHO quite relaxed COC criterion of something like 0.030 mm, good enough if you never print larger than 5x7 inches or thereabouts. I wouldn't confuse them with what is important for me, if the exact DOF is important to me.

And to add a reference to another oracle (besides the one with presumed Scottish roots who also posts here):
http://toothwalker.org/optics/dof.html
He also pays attention to the differences in the foreground and background blur and 'bokeh'. His conclusion at the end of that page is worthwhile if one needs a quick idea.

His explanation of the theory is very good, including the differences that the optical design (pupil factor) has on the theoretical DOF which is only valid in a simple optical model.

Cheers,
Bart

Khalid's grandfather told me other things also. How I could move the distance scale and line them up with apertures. How I could make the subject behind /front go out of focus

Imagine just moving and seeing on the lens.

The only Nikon lenses that have such markings are the older ones. No ' G ' lens has such distance scale markings that I have illustrated here. Many ZF lenses have such markings.

All Leica Lenses, from day one , to this day have these markings.

The photo I have posted in the analog section taken in Montreal was shot using the techniques I learnt from Fahim.

Neither Khalid's grandfather nor I intend to discuss which lenses have markings and what color
they are and what identification marks they have.

Both of us have other important things to do.

Go and ask the Oracle about various makes of lenses and if they have markings and what type and what for and what color.

Jerome Marot said:

Maybe, maybe not. Amongst Nikon, Canon, Pentax, Sony and Olympus, which of them still manufacture AF lenses with these markings today?

Click to expand...

Hi Jerome,

Most of my Canon lenses do, even though the COC criterion on which they are based is of limited use.

Cheers,
Bart

Hi, Jerome,

Jerome Marot said:

This is correct, but it isn't the answer to my question. I realize I did not ask it in an understandable manner.

The question is "what does this mean in practice?". We can only take pictures with the cameras we have. Yet, sometimes, we want a given depth of field (small or large). Can we get what we want with the cameras that exist, considering what lenses are available for a given format? For example, you are talking about a f/2 100mm lens for 6x7 above, while no such lens ever existed for that format.

So, let me rephrase the question and split it in parts.

The question is linked to what lenses are available. Obviously, we can get the typical depth of field of a 24x36 50mm at f/8.0 and 3m distance in any format.

Click to expand...

I imagine so (I haven't looked at any numerical examples).

First: thin depth of field.
We can get thin depth of field in 24x36 (full frame) by using fixed focal lenses opened at typically f/1.4, sometimes more. These apertures exist at 21mm (Leica only), 24, 35, 50, and 85mm. Above that we can only find f/2.0 lenses. What happens in other formats (smaller or larger) with the lenses which are available? There is a f/0.95 25mm lens available for half frame. For 4.5x6, lenses max out at f/1.8. The Leica S system maxes out at f/2.5. For 6x6, lenses max out at f/2.0 (Hasselblad and Rollei) or more commonly f/2.8. For 6x7, one lens is f/2.8 (Mamiya RZ), but they typically max out at f/3.5.

Click to expand...

Well, we might want to look at the depth of field afforded by the specific combinations you mention, to get some insight into this.

I'll have to adopt some arbitrary values that will be common to all cases. How about:

• Shooting distance: 10 m
• COCDL: 1/1400 the frame diagonal

If you don't mention a specific focal length, I'll pick one that seems reasonable.

Now the cases:

Full frame 35 mm (36 x 24 mm). 35 mm, f/1.4. Double-sided DoF: 8.1 m
Half frame 35-mm (24 x 18 mm). 25 mm, f/0.95. DS DoF: 7.1 m
4.5 x 6 (42 x 56 mm). 50 mm, f/1.8. DS DoF: 8.22 m
6 x 6 (56 x 56 mm). 50 mm, f/2.8. DS DoF: 21.3 m
6 x 6 (56 x 56 mm). 50 mm, f/2.0. DS DoF: 11.4 m
6 x 7 (56 x 67 mm). 60 mm, f/3.5DS DoF: 15.0 m

The question is different if we want the convenience of zoom lenses. Zooms max out at f/2.8 (Olympus has a f/2.0 lens) for interchangeable lens cameras. Obviously, we cannot get a depth of field as thin with a half frame sensor than with a full frame sensor (for the same picture) since their zooms also max out at f/2.8. But if we use, say, a 18-50 f/2.8 lens on a half frame sensor, to what aperture does it correspond on a full frame sensor?

Click to expand...

I assume you are speaking of the use of the same lens on both cameras. Again I will assume a consistent object distance, 10 m.

Half-frame 35-mm. 18 mm, f/2.8. DS DoF: Infinite
Full-frame 35-mm. 18 mm, f/2.8. DS DoF: Infinite

Half-frame 35-mm. 50 mm, f/2.8. DS DoF: 5.0 m
Full-frame 35-mm. 50 mm, f/2.8. DS DoF: 7.8 m

To get the DoF exhibited on the half-frame camera on a full-frame camera (50 mm case), the f-number will have to be about 61 mm.

<snip>

Second: large depth of field.
This is typically only a problem in macro or close ups. For 24x36, we are usually limited by diffraction which degrades resolution above f/16 or f/11 with high resolution sensors. We can use smaller sensors with smaller focal lengths at a larger aperture (your typical digital P&S is usually a quite efficient macro machine), but up to which resolution? Very small digital sensors have minuscule pixels and the limits of diffraction appear sooner (as early as f/2.8 usually).

Click to expand...

Yes, these are true dilemmas.

Keep in mind that the approximation used in some formulas do not always apply when the distance between the object and the lens is similar to the distance between the sensor and the lens.

Click to expand...

We do not use such formulas here!

Best regards,

Doug

Hi Doug/Bart.

I have printed 8x10 inches using these techniques.
I could easily have drum scans made of film where landscapes I have taken will be perfect for considerable more enlargement. There is no magic here. Set an aperture to f16 ( the old sunny rule ). And you really can get to infinity from 10-15 meters without a problem.

Most people have seen the photos I post. I use shallow DOF in very many of them.
There I make sure of the focus, and do not use rough and ready methods. Because my f-stop is below f=2.8; I use f=1.4 very very many times. I have to be careful.

At f=5.6, 8, 11, 16, 22 one can be a little lax.


I am telling people, easy to use methods. Simple to understand. Simple to use.

I guess I was wrong to waste everyone's time. My apologies.

Best regards.

fahim mohammed said:

The only Nikon lenses that have such markings are the older ones. No ' G ' lens has such distance scale markings that I have illustrated here. Many ZF lenses have such markings.

Click to expand...

To this day, all Nikon fixed focal lenses have such markings. It just so is that the rotation of the lens for focussing is so small in recent lenses that the only mark left is at f/16, but the mark is still there.

Jerome Marot said:

To this day, all Nikon fixed focal lenses have such markings. It just so is that the rotation of the lens for focussing is so small in recent lenses that the only mark left is at f/16, but the mark is still there.

Click to expand...

Jerome, since you are nitpicking..

I have shown you a photo of a lens to illustrate.
Bring me a modern Nikon lens with similar markings.

Or better still take a photo of the Nikon lens you are talking about and provide a similar explanation to that I have provided with the Leica lens.

It has a marking, you say. Good. Show me what I showed you with the Leica. An example of aperture and distance setting scales. Show me how you would use the method I talked about.
Use the ' G ' lens. You say it has a marking. Let's see how you use it.

I am always willing to learn.

Hi Fahim,

fahim mohammed said:

...I guess I was wrong to waste everyone's time. My apologies.

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You did not waste my time. I am solely responsible for that. Re. this on-going debate, I have truly enjoyed following it. Allow me to cite an old Turkish parable, attributed to the famous philosopher Nasreddin Hodja.

Once when Nasreddin Hodja was serving as qadi, one of his neighbors came to him with a complaint against a fellow neighbor.The Hodja listened to the charges carefully, then concluded, "Yes, dear neighbor, you are quite right."
Then the other neighbor came to him. The Hodja listened to his defense carefully, then concluded, "Yes, dear neighbor, you are quite right."
The Hodja's wife, having listened in on the entire proceeding, said to him, "Husband, both men cannot be right."
The Hodja answered, "Yes, dear wife, you too are quite right."

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Cheers,

Doug Kerr said:

Full frame 35 mm (36 x 24 mm). 35 mm, f/1.4. Double-sided DoF: 8.1 m
Half frame 35-mm (24 x 18 mm). 25 mm, f/0.95. DS DoF: 7.1 m
4.5 x 6 (42 x 56 mm). 50 mm, f/1.8. DS DoF: 8.22 m
6 x 6 (56 x 56 mm). 50 mm, f/2.8. DS DoF: 21.3 m
6 x 6 (56 x 56 mm). 50 mm, f/2.0. DS DoF: 11.4 m
6 x 7 (56 x 67 mm). 60 mm, f/3.5DS DoF: 15.0 m

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See? The assumption that large format has smaller depth of field is not true in practice, 35mm often wins because very large aperture lenses are available in that format (which is what I wanted to demonstrate here). Most discussions about depth of field and sensor size forget about which lenses are available.

I assume you are speaking of the use of the same lens on both cameras. Again I will assume a consistent object distance, 10 m.

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Actually, no. I always assume that the photographer wants to make the same picture: same perspective (therefore same distance) and same framing. So on a smaller sensor, we need a shorter focal length. Under these assumption, calculations show that a f/2.8 zoom on a half frame DSLR will give you about the same depth of field as a f/4 zoom on a full frame DSLR. Which, I think, is the information that counts. By using a half frame DSLR, you lose one stop of depth of field.

In actual photographic practice, what counts is how to choose a given system to achieve the picture you want or, conversely, what the limitations of a given system will be.

Now, who wants to discuss the Brenizer method?

fahim mohammed said:

I have shown you a photo of a lens to illustrate.
Bring me a modern Nikon lens with similar markings.

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Fahim, the link to photographs of all Nikon fixed focal lenses was in my post. For example, here, you will see that the 24mm f/1.4 G lens has markings for f/16 and f/11. You use them as you always did.

If you can't click, I will try to directly link the image here. I am not sure it will work, however.

Hi Cem.

Nice to hear from you. Hope the family and you are fine.

I am waiting for that miraculous Nikon ' G ' lens to be shown and illustrated with an example of how to use it in a way similar to that which I illustrated with the Leica Lens.

Kindest regards.

Bart_van_der_Wolf said:

Most of my Canon lenses do

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The answer was that Nikon, Canon, Pentax and Sony all still manufacture AF lenses with these markings today, only Olympus doesn't (and won't be able to with µ4/3 lenses, due to the way their focussing works).

fahim mohammed said:

I am waiting for that miraculous Nikon ' G ' lens to be shown and illustrated with an example of how to use it in a way similar to that which I illustrated with the Leica Lens.

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I can't take a picture of a Nikon lens for you, because I don't own any, but what about clicking on the links I posted? You will find a picture of the Nikon lens showing quite plainly the markings for f/16 and f/11. It is on the manufacturer web site.

Jerome, this is what I wrote..

" No ' G ' lens has such distance scale markings that I have illustrated here "

Read my sentence above. See what you are illustrating. Take some time.

' such distance scale markings ' is what I wrote. Not one mark, not two marks, but ' such distance scale markings that I have illustrated here '

The example I gave was for f =5.6. I could have given for f = 4, f=2.8, f = 2, f = 1.4
Please show me that with the ' G ' Lens.

I used an example at f= 5.6. Show me such an example Jerome with the ' G ' lens that you have linked
to. Show me how to set the distance scale at f=5.6.

Either you can or cannot. Let's not waste further time on this. Either you can or you cannot.

fahim mohammed said:

Hi Doug/Bart.

I have printed 8x10 inches using these techniques.
I could easily have drum scans made of film where landscapes I have taken will be perfect for considerable more enlargement. There is no magic here. Set an aperture to f16 ( the old sunny rule ). And you really can get to infinity from 10-15 meters without a problem.

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I have no problem with that, because there is no hard limit between sharp and unsharp. One just should remember that the output magnification is one of the factors in adopting a COC. Taking a COC of 0.030mm (which is 4-5 pixels (or more) of blur on most sensors) means that the potential for enlargement with full detail is limited. An image with a COC can be enlarged 4x (36 mm becomes 144 mm) before we can visually detect it to be less sharp than an image that was taken with higher quality standards. If that reduced sharpness is important, depends on the image.

Most people have seen the photos I post. I use shallow DOF in very many of them.
There I make sure of the focus, and do not use rough and ready methods. Because my f-stop is below f=2.8; I use f=1.4 very very many times. I have to be careful.

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Indeed, no problem with that either. You use the limited DOF to guide the eye towards what you think is important in the image. Exactly as it should be used. In addition, as a side effect, the in-focus areas are probably sharper that they would be with much narrower apertures. It strengthens what you intend to convey.

I am telling people, easy to use methods. Simple to understand. Simple to use.

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No problem with that either, although it's not the whole story and some might want to also hear that part before they dismiss it as a distraction.

I guess I was wrong to waste everyone's time. My apologies.

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No need for that. As Cem illustrated, we all are right ..., about a part of the whole story. It's the collective of information and relativation that counts, and it's not something fixed for all situations. One needs to shop selectively depending on the requirements.

Cheers,
Bart

fahim mohammed said:

Jerome, this is what I wrote..

" No ' G ' lens has such distance scale markings that I have illustrated here "

Read my sentence above. See what you are illustrating. Take some time.

' such distance scale markings ' is what I wrote. Not one mark, not two marks, but ' such distance scale markings that I have illustrated here '

The example I gave was for f =5.6. I could have given for f = 4, f=2.8, f = 2, f = 1.4
Please show me that with the ' G ' Lens.

I used an example at f= 5.6. Show me such an example Jerome with the ' G ' lens that you have linked
to. Show me how to set the distance scale at f=5.6.

Either you can or cannot. Let's not waste further time on this. Either you can or you cannot.

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Indeed no Nikon G lens has markings for f=5.6. Sorry to have wasted your time.

Jerome, you have my respect and my admiration.

Warmest regards.

Hi, Fahim,

Yes, that was a lovely facility on the lenses of teh time.

Note that it is predicated on some particular COCDL, adopted by the manufacturer, typically on the "human visual acuity" basis. And thus it of course applies to the use of the lens on a certain format size camera (often, of course, there weren't any others it it would fit, at the time).

Your parable was lovely, too. You are well named.

Best regards,

Doug

fahim mohammed said:

Jerome, you have my respect and my admiration.

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I don't understand how I have earned it.

Hi Jerome,

fahim mohammed said:

Jerome, you have my respect and my admiration

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Jerome Marot said:

I don't understand how I have earned it.

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I do. Anyway, sometimes just knowing something is enough; understanding is not necessary.