Film exposure in LF. How do you do it?

One can't carry an endless supply of film! It's also an expensive waste to have a large percentage of duds!

For a few of us, enough experience with a particular film and belows is sufficent. One simply judges the lighting from the clouds, sunlight, shade and time of day or flash.

Still one really need some kind of objective meter. Is it worthwhile to use a Sinar or other probe for the back or do you use a Minolta or Pentax meter?
Is that what you only do or do you also pull a Polaroid to confirm the settings? Anyone use a digicam as their "Polaroid" for this? Or do you guestimate and bracket?


Asher

If you shoot LF you probably are doing landscape -- not shooting your kids jumping about --, so the best way is to bring an incident and/or spot, but mostly incident meter. I have one that is spot and incident with zoom.

I just point the "face" of the meter to my camera: f: 16 125/s, so my ship is dark -- for the ones shooting tankers -- I open half to 11.5 and shoot. If it is C-Neg, there is no problem. I did my urban landscape in japan with an incident Minolta reader, sooting VELVIA ISO 50 and carried only two holders --total 4 "plates"-- for the entire afternoon of shooting. It is just a different sport than "spray and pray" of a reflex.

PS be careful when shooting close to a subject to compensate for "BELLOWS FACTOR" that is very important and no image will come out if this is not taken in to consideration...

Asher Kelman said:

One can't carry an endless supply of film! It's also an expensive waste to have a large percentage of duds!

For a few of us, enough experience with a particular film and belows is sufficent. One simply judges the lighting from the clouds, sunlight, shade and time of day or flash.

Still one really need some kind of objective meter. Is it worthwhile to use a Sinar or other probe for the back or do you use a Minolta or Pentax meter?
Is that what you only do or do you also pull a Polaroid to confirm the settings? Anyone use a digicam as their "Polaroid" for this? Or do you guestimate and bracket?


Asher

Click to expand...

Hi Asher, hi Leo !

I use a Minolta Flashmeter V and a Seconic. Had a Pentax Spotmeter - it stopped working after being ignored for a long time . . .
As Leo said: incident metering and VERY important indeed: the "bellow-factor" (is it really the word in english?) at close distance stills with long bellow-extension. I had about 2 stops to add very often and sometimes more. That´s when you´re very happy about PLENTY of strobe-power . . . . - the only times i really need all the about 10000Ws of my Balcars . . usually i work with around 2400Ws max. when shooting people.

Polaroid rulez!!!

best, Klaus

Strange noone is using spotmetering of different parts of the subject?

Also, what is your formula for dealing with bellows extention?

Asher

Asher Kelman said:

Strange noone is using spotmetering of different parts of the subject?

Click to expand...

I do! I use a Pentax digital spotmeter to measure specific areas of the scene, then using the exposure portion of the Zone System (modified for color), I apply those readings to calculate my desired exposure. (I expose to preserve key highlights when using chrome film and do the opposite -- expose for the key shadows -- when using negative material.)

Also, what is your formula for dealing with bellows extention?
Asher

Click to expand...

Mine is different than most and it tends to confuse many, but it works for me: I tend to think of bellows factors as f-stops.

Assume we are using a 110mm lens. When focused at infinity, we will have very close to 110mm of bellows extension as measured between the film-plane and lens flange. I will think of that extension as an f11 base aperture for that lens. Now as I focus closer, I need to extend the bellows further. So let's assume I am focused on something quite close and now have 160mm of distance between the film-plane and lens flange; I now think of this bellows value as f16. Since I know the difference between f11 and f16 is one stop, I know I need to add exactly one stop to the "f16" bellows extension to my measured eposure for it to be accurate for my "f11" lens.

Cheers,

RE: Bellows Compensation: The easiest, fastest and very accurate --if not the most accurate -- is to place a target of specific size on the subject and measure the size to a "ruler" that will dictate the compensation like -1/3, 1/5, etc.

This is distributed by Calumet and can be photocopied or even copied by hand. I glued a copy on my light meter for emergencies.

I just did a google search and found this that seems to be the same principle and ready to be printed -- I should write a disclaimer about a product that I have not tested etc etc --

http://www.southbristolviews.com/pics/Graphic/SBVCALC.pdf

Leonardo, I think you are thinking of the QuickDisk.

Here is a link to the home page:

http://www.salzgeber.at/disc/index.html

And best of all it is FREE!

Asher

as often shooting outside, and not alwith beeing able to control the wheater, I checked alwith the contrast, in these days, with a Seykonic spotmeter. As it has a incident light-bulbe as well, it' s pretty usefull.

I don't know if this helps or not Asher but my cousin who has gone back to old box cameras carries or did carry a D80 with him to use as a meter. He would take a shot or two then go home and develop them. He now pretty much has it in his head with just a look at the subject.

Will Thompson said:

Leonardo, I think you are thinking of the QuickDisk.

Here is a link to the home page:

http://www.salzgeber.at/disc/index.html

And best of all it is FREE!

Click to expand...

Of course, Will,

That's the inverse square law:

(Bellows extensionin mm)(Bellows extensionin mm)/(focal length in mm)(focal length in mm).

However, that doesn't deal with distribution of light from the sky to the tree shadows.

So a simple pocket mm ruler measuring the extension would be the fastest way to go for the bellows factor it seems.

Asher

Before I misplaced my Minolta spotmeter, I'd choose a part of the image as a baseline and decide what zone I wanted it to end up in. I'd meter it and then alter the metered reading to compensate for the difference between desired zone and zone V. With TMAX-100 I'd almost always meter it as if it was ISO 50 instead of ISO 100, to compensate for the complete lack of toe on the film (coming from digital I'm used to having a lot of room in the shadows). Sometimes I'd spot meter other areas to make sure that contrast levels weren't too far off.

Since I misplaced it (it's got to be somewhere around the house...) I've just been carrying my 20d with a 50mm lens. Heavier than I'd like, but I can check the histogram of my LF shot.

I like spot metering because I feel like I've got more positive control than incident or averaged metering. I'm very consciously choosing a particular grey level for a particular part of the scene. You don't get that any other way - everything else assumes there's a perfect exposure for a scene and tries to get it. Ideally I'd use a very small, lightweight DSLR with built-in spot metering, so I'd get a digital polaroid as well as the spot metering.

You can use the inverse square law directly: ((E/F)^2)/1.41 where E is total extension and F is the focal length of the lens; dividing by 1.41 (sqrt 2) converts this into a direct apertuyre value. So if you have a 150mm lens and total extension is 180mm, your new aperture factor will be, ((180/150))^2/1.41 or (1.2)^2/1.41 = 1.44/1.41. The problem with this in the field is you now need to divide. In the above example, 1.44 is very close to 1.41, so the result is close to 1; I can safely assume 1 full stop. However, say your extension was 200mm. Now our formula looks like, (200/150)^2/1.41 or 1.78/1.41. Quick -- the light is fading fast -- what is 1.78/1.41? (I don't know exactly unless I grab a calculator, but it's probably close to 1-1/3 stop.) I can use this formula on my exposure times though, and pretty easily -- all I have to do is leave out the dividing by 1.41 and multiply my exposure time directly. (Don't forget to add in for reciprocity when exposure times exceed 2 seconds!)

The above is a bit complex for field use -- having to square numbers in my head and/or divide then convert from EV to an actual aperture -- and why I use my previously mentioned method; I just find it easier to apply in real shooting conditions.

Another useful (and realtively easy) formulae if you know magnification is: Aperture factor = f*(1 + M), where f is the marked f-stop on the lens and M is the magnification ratio at the film or sensor. Here if you are at 1/4 life size as seen on the GG and your lens is set to f22, your effective aperture would be 22*(1.25) or f27.5. This formula is basically what the Expo-Stick uses and is somewhat easy to do in my head IF I know the magnification.

In eany case, the following table is helpful to convert derived apertures into normal 1/3 stop aperture-equivalents (I print this onto a label and stick it to the side of my meter):

5.6 6.3 7.1 8 9 10 11 13 14 16 18 20 22 25 28 32 36 40 45 50 56 64

Cheers,

Jack_Flesher said:

You can use the inverse square law directly: ((E/F)^2)/1.41 where E is total extension and F is the focal length of the lens; dividing by 1.41 (sqrt 2) converts this into a direct apertuyre value. So if you have a 150mm lens and total extension is 180mm, your new aperture factor will be, ((180/150))^2/1.41 or (1.2)^2/1.41 = 1.44/1.41. The problem with this in the field is you now need to divide!!!!!!!!

-- all I have to do is leave out the dividing by 1.41 and multiply my exposure time directly. (Don't forget to add in for reciprocity when exposure times exceed 2 seconds!)

Cheers,

Click to expand...

Jack, a simple ruler to measure extension for each lens, with time-multiplier would be really easy!

Asher

Asher Kelman said:

Jack, a simple ruler to measure extension for each lens, with time-multiplier would be really easy!

Click to expand...

Indeed -- and that's the idea

Jack, I was thinking that the units on the ruler would be the aperture-muliplying factor instead of "cm"!

Asher

That would work fine, but you'd need a different scale on it for each lens you owned -- for some of us, the ruler would be bigger than our pack A tailor's cloth tape measure is a good option for the tape end. As for the calc, if you can do them in your head, great. Otherwise a small calculator... Or, how about a simple, homemade circular slide rule scaled for aperture values? Hmmm

Pardon my ignorance, I thought that bellows extension was only needed for objects closer than the 'close focusing distance' of that particular focal length, not really something needed for landscape shooting, or am I wrong?

Ben Rubinstein said:

Pardon my ignorance, I thought that bellows extension was only needed for objects closer than the 'close focusing distance' of that particular focal length, not really something needed for landscape shooting, or am I wrong?

Click to expand...

Absolutely correct Ben!

(If you look at how much extension you have to add to focus on something say 2 meters away with a 150mm lens, you will note it only adds a little... Using the inverse square formula above you will see the result is so close to 1 as to be insignificant as respects bellows factor.)

Cheers,

Dear All,

I would like to give some information about metering with a view camera and LF.

We all know that a film has a certain, limited contrast range/dynamic. With transparancies it is about 6 to 6 1/3 f-stops, with colour negatives it is about 7 f-stops, and with B&W film around 10 f-stops.
Beside the obvious problem and difficulty to "fit" your scene contrast into these 6 stops of a transparancy, the most important is that you are limited by the print medium: the best offset print, with the best screening, the best inks and the best paper can ONLY print 4 f-stops (from details in the high-lights to details in the shadows), or in other words, these 4 f-stops correspond to 1.8 density values in print.

I pass on the fact that the E6 processing will add to the contrast with the Gamma factor of 1,7, but basically, if you want to print something with details in the shadows and in the high-lights, then the MEASURED contrast between these 2 points SHOULD NOT BE OVER 4 f-stops. This EVEN if your film can accept more!

What does this mean? It becomes obvious that any "GREY" metering does not make any sense. The "Grey Card" is only a mathematical way to balance the light in lightmeters, a method and standard on which manufacturers agreed (18% reflecting grey) which DOES NOT give ANY information of the contrast in your particular scene. You might have a right and well exposed film, by making a grey-metering, but you won't have any clue of the contrast and if you would be able to print what you have seen.

The only way to have control over the whole printing process and to make sure that you will have details in the zones of your images where you want it, is to make a 2-point CONTRAST METERING.

To make a 2-point contrast metering, there are 2 methods, both metering the REFLECTED light from the subject, NOT the incident. Reflected light can be very different to the incident one (absorbtion, reflections, angle of metering, ...).

One can do a metering of the reflected light either by using a spotmeter or then metering this reflected light IN the film plane of the camera:

1. Spotmetering

This is a very good method, provided one makes the metering excatly in the same axis as the optical axis of the camera (by moving around your scene you will notice that the reflection of the light is different), and provided that you do calculate as well the "Correction Factor" due to your belows extension.

2. Metering of the reflected light in the film plane

There are different probes out in the market, from different manufacturers. This probe can be slided inside the groundglass, just in place of the image plane, there where the light is hitting the film, thus metering EXACTLY the amount of light hitting and exposing the film.
This method is of course the most precise and convenient, taking automatically in account any bellows extension and any filter placed in front of the lens.

3. How to meter?

For both methods, spotmetering and metering in the film plane, one makes a 2-point metering: the first point to be measured is e.g. the darkest point in your scene for which you still wish to have some little details in the print. You will measure this point and give it an exposure value of 2 f-stops UNDER (Zone 3) the medium grey (Zone 5): in other words, you under-expose it by maximum 2 f-stops.

Then you measure the point in the high-lights for which you still want to have some little details in the print: you should then over-expose this high-light by maximum 2 f-stops (Zone 7).

The total of contrast in your scene will then be exactly 4 f-stops, just the amount which will be printable. You will make sure that you have details in your print and that you have those details at the place where you want it to be!

You have FULL control of your contrast and of your image rendering in print, by doing this way.

Now, this is easy to achieve in studio (to balance the light to have -2 and +2 f-stops between the shadows and the high-lights): you just have to make use of your light and set it up the right way to achieve this.

When you are on location, you won't have any other alternative, if the contrast between your 2 extreme points exceeds 4 f-stops, than to wait for a better, less contrasty day, WHEN shooting on transparancies or colour negatives. If you are using B&W films, then you have the possibility to compensate and correct the excessive (or to little) contrast by adusting the B&W process, means by under- or over-developping your film: that is by using the so-called "Zone System", made famous by Anselm Adams. I won't elaborate on this, since there are many books to get the information.

4. Compensating for the Bellows Extension with a Spotmetering

Since the spotmeter DOES NOT take in account the lost light hitting the film due to the bellows extension (or due to a filter in front of your lens), you will have to calculate this factor.

There is a formula to calculate this very precisely, but I will give you here the different factors depending on the different reproduction scales you shall encounter. Here the values of compensation:

- below a reproduction of 1:8 you can use the exposure value given by your spotmeter
- for a reproduction scale of 1:8 to 1:5 use a factor of +1/3 f-stop (increase exposure by 1/3 of f-stop)
- for a reproduction scale of 1:4 use a factor of +1/2 f-stop
- for a reproduction scale of 1:3 use a factor of +2/3 f-stop
- for a reproduction scale of 1:2 use a factor of 1 & 1/3 f-stop
- for a reproduction scale of 1:1 use a factor of 2 f-stop
- for a reproduction scale of 2:1 use a factor of 3 f-stop
- for a reproduction scale of 3:1 use a factor of 4 f-stop
- for a reproduction scale of 4:1 use a factor of 4 & 2/3 f-stop
- for a reproduction scale of 5:1 use a factor of 5 f-stop

These factores are easy to keep in mindd, and are the same for any lens used. No need to make other calculations, or to take a calculator with you. You don't even need to have a ruller, to calculate your reproduction scale (magnification).

How to understand "Reproduction Scale" and how to calculate it?

- 1:8 means that you are having an image on your groundglass which is 8 times smaller than your subject
- 1:1 means that your image has excatly the same size as your subject
- 2:1 means that your image is 2 times larger than your subject
- etc ...

So all you have to do is to measure a part of your subject and measure the same part on your groundglass, then compare it to get the reproduction scale.

I hope this can help some to have a better control of their images. Try it out and you won't need to expose x films to be sure to have the right one. But more importanly, it gives you total control.

Best regards,
Thierry