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Depth of field

Antonio Correia

Antonio Correia

Well-known member
How I did it
  • In this table I have choosen my camera, my lens and my distance (I use meters of course).
  • Consulting the table, I could see that
    • if I set a distance of 1 meter in the lens and
    • if I use f/22 that would give me a depth of field between 0.38 and infinity.
  • Then, I measured the distance with na instrument like a tape or whatever, between the sensor plain/layer/surface to a target which was 1 meter away.
  • I target the central point of the focusing screen to that point and focus.
  • I switch off the auto focus from the lens.
  • I set the aperture at f/22
  • I compose the scene
  • I placed an object at 40 cms (40 cms = 0.40 meter)
  • I now have the object and infinity in focus.
  • I didn’t care with the speed, or I do and have to think the hole thing over again.
    • If I had too much light I would have used the NDF and/or the CPF.
    • I used flash because now I am a maniac of this kind of light, which is gorgeous as you can see here in my photos and here.
Next photo I want to do – if I got the time because my sun asked to go and shoot kitesurf again tomorrow evenning – will be envolving 3 planes/surfaces/areas:
  • Near the lights of the car - 0.83 cms
    [*]Medium distance the car door or so - 1.26 m
    [*]Far distance, like the street.
At f/2.8 the 16mm with the lens focused to 1 meter will give me sharpness from 0.83 to 1.26 – the street at the far end will be out of focus and so will be the main lights.

How about this ?
Tell me !
176949873-L.jpg
 
Asher Kelman

Asher Kelman

OPF Owner/Editor-in-Chief
Excellent shot. I love this image as it is.

Antonio, I'd like to see more of your desk in another picture and use the frame of the door (according to Magritte fashion) as the boundry on the right and perhaps get the window in too. I'd consider putting the flowers on the other side of the door/ archway.

You'd need a wider lens but then your DOF would be correspondingly greater.

I'm concerned about the f 22 in this current picture as you might be degradng the picture for printing. Depending on the ofcal length you may be limiting your resolution by diffraction, although on the screen it looks wonderful.

I always learn from your work as you stimulate my own thinking about composition.

Asher
 
Asher Kelman

Asher Kelman

OPF Owner/Editor-in-Chief
Excellent shot. I love this image as it is.

Antonio, I'd like to see more of your desk in another picture and use the frame of the door (according to Magritte fashion) as the boundry on the right and perhaps get the window in too. I'd consider putting the flowers on the other side of the door/ archway.

You'd need a wider lens but then your DOF would be correspondingly greater.

I'm concerned about the f 22 in this current picture as you might be degradng the picture for printing. Depending on the focal length you may be limiting your resolution by diffraction, although on the screen it looks wonderful.

I always learn from your work it stimulates my own thoughts about composition.

Asher
 
Antonio Correia

Antonio Correia

Well-known member
The picture herewith is a crop of the original.

It was wider.

If I was using a wider lens - which I don't own - I would work with the same procedure.

KISS - Keep It Simple and Smart

I did not care about defraction as it would occour on the end of the rectangle... Or am I wronge ?

As this is for the Nikolai assignment I will shoot another one soon. At least I think I will. :)

Cheers and thanks for commenting.
 
B

Bart_van_der_Wolf

pro member
Antonio Correia said:
I did not care about defraction as it would occour on the end of the rectangle... Or am I wronge ?
Click to expand...


Antonio, the images are not showing up on my side of cyberspace, maybe something to do with Smugmug? However, although I'm currently not able to judge the images, I can comment on diffraction in general. I don't recall whether you shoot a 1.6 cropped sensor camera or a full-frame one, but diffraction starts to deteriorate all image detail once you go beyond a certain F-stop.

The general rule of thumb I use for determining the 'break-even' point (between increasing DOF and reducing sharpness) is the aperture at which the diffraction pattern diameter becomes twice as large as the sensel pitch. The sensel pitch can be approximated by dividing the size of the sensor array in millimetres by the number of sensels/pixels. The diameter of the diffraction pattern (more specifically its first minimum from the center) can be approximated by 1.3542 x f/# (in microns) for green light.

That means that for a camera with a 6.4 micron pitch sensor array (e.g. EOS 20D) the limit is at approx. f/10, and I personally consider that already a bit too much deteriorated (although recoverable with special software). A 1D Mark II or a 5D class camera (8.2 micron pitch) could get away with f/11 or maybe f/13. The 1Ds Mark II and 1D Mark III (7.2 micron pitch) would be limited to f/10 or maybe f/11.

Choosing a smaller aperture will result in visible loss of sharpness and 'effective' DOF.

Bart
 
B

Bart_van_der_Wolf

pro member
Antonio Correia said:
Thank you Bart.

I know little about defraction. :(
But you gave interesting clues. Thanks. :)

Than, I am going to turn to f/10 for the next pictures on this assignment.
Click to expand...

We're here to help each other, and enjoy beautiful images.

One more remark about diffraction, in the numbers I mentioned I assumed the images to be suitable for large prints. If you shoot for web publishing or other down sampled imaging only, then all blur will be reduced in size as well, so you'll gain apparent resolution/DOF and you can tolerate more diffraction.

The images you linked to are now showing up again, Smugmug is back.

Bart
 
K

Kathy Rappaport

pro member
Antonio- very nice

I really liked your creativity in that assignment. My entry isn't finished yet. My subjects decided that they were not being paid to sit still and they did not want to obey. (I tried to shoot my dogs on my bed at night without flash - using ambient light, high ISO and the Sigma 12-24). My black dog needed fill and my tan dog wouldn't cooperate. I have to start fresh with new subjects and either more dog biscuits or a whole new setting without dogs.
 
Antonio Correia

Antonio Correia

Well-known member
I shot a different picture this time, may be a little in a hush :(
In fact I used f/11 and I could not get so better results in terms of DOF.
May be. No. I have gained in terms of deffraction sure, but lost in DOF

I want to do it again. Don't know exactly when...
I used here a little fill flash

 
B

Bart_van_der_Wolf

pro member
Antonio Correia said:
I have gained in terms of deffraction sure, but lost in DOF
Click to expand...

Well, it is a trade-off! You gain in quality where it matters, the in-focus area where you want to draw attention to, but the very out-of-focus (OOF) areas stay that way. It's a typical case of "there is no free lunch". Personally I want my in-focus area to have optimal quality.

If extended DOF is the goal, then there are techniques like "focus stacking" or lens tilt, depending on the circumstances either one of them might be preferable to stopping down the lens too much.

Bart
 
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