What am I doing wrong?

[csant]

I have been shooting medium format for years. I moved up into 4x5 and then 5x7 a few years ago, and have been shooting quite a lot, with a few different lenses, both modern and historical. And then some time not too long ago… I fell for the temptation and moved up to 8x10… Some of the lenses I have been using for 5x7 work for the larger format, too, and some are only for the big thing.

I have never had any issues with exposure, I use a spot meter and mainly expose "manually", with a lens cap. Exposure works fairly accurately (I am a musician, it's easy to measure 1/4er, 1/5th or even 1/10th of a second ;) ) - or at least, I have never had any exposure problems… until I started using 8x10. Virtually all of my 8x10 negatives are underexposed. I started compensating for bellows extension much more consciously than for the "smaller" 5x7 and 4x5, I am paying special attention to exposure, development happens exactly the same way as the other sheets… And yet, I seem to be always on the low end. :confused:

What am I doing wrong? Is 8x10 *that* much more sensitive to bellows extension? Are lenses with long focal length that claim to have a certain aperture to be treated differently than shorter focal lengths with the same aperture? Are large negatives a different beast altogether than smaller ones? Is light metering for an 8x10 negative to be treated differently than for smaller negatives? Any hints, suggestions or shared experiences are welcome.

claudio

[Gary Beasley]

You may be running into reciprocity problems. Best thing would be to do a Zone system style calibration on the camera, lens and film system you are using.

[Stefan Findel]

Claudio, moving up from 4x5 or 5x7 to 8x10, you should not experience any difference regarding exposure. There is nothing different or mysterious about 8x10, except that the larger neg will show any flaws in exposure, focus or whatever more readily. As Gary suggests, depending on what film you use, you may run into reciprocity failure, if, due to the larger format, you stop down more and have longer exposure times. That should not really start until about a 1 sec. or more. Other than that I see no reason to have the problems you describe. Or did you change anything else? You are using the same film? You have the same problem with those lenses you have been using on the smaller formats, or maybe only with lenses you have not used previously? Sometimes a lens may have the wrong aperture scale, if it was mounted in the proper size shutter, but with a wrong scale not meant for that focal length.

[csant]

Gary and Stefan, thanks for the feedback. I don't think I am hitting reciprocity issues with 1/2 sec exposures, and yet less I believe my technique goes down the drain for one format only. At least one lens was recently shot on both 8x10 and 5x7 - admittedly, under different circumstances. But it only gave me problems on the big thing. The question about the film made me wonder… I do use the same brand and model, Fomapan 100, but obviously from a different box… Might there be something wrong with the 8x10 batch I am using? I'll expose the remaining sheets for test shots, and will see whether I get an answer there - and whether the next box will give me the same kind of problems…

[Stefan Findel]

I have had numerous problems with films (and papers) from smaller manufacturers, who cannot afford the quality control of, say, Kodak. This is why I shoot only TMax films. Like you I shoot at long shutter speeds (typically 1/8 to 4 sec), and that is another reason for me to use TMY-2. Besides Kodak's excellent quality control, the reciprocity response is much better to deal with. I have not been happy with Foma or Efke films.

[ki6mf]

Some things to consider. Have the shutter speeds checked. Is you development method, agitation method different. Is the developer straight or diluted ( I personally go for longer diluted times, 14 minutes is my normal, for developing this allows for more control, w minutes between each n- or + times, when shortening or lengthening development times to control contrast. I would retest film speed and normal development times and always use stop watch for longer exposure times

[Diane Maher]

What subjects are you shooting? How much are you stopping down the lens?

[csant]

Wally, it's going difficult to have my shutter speeds checked ;) I doubt I am making exposure mistakes on one format only, and always the same... Developer is diluted the same way, agitation is "the same" (well, the negatives are bigger, but I doubt that would cause significant difference, since the technique of shuffling the negs is the same), at the same temperature. Again, there might be minimal differences each time (I am human, after all), but I can't understand why those differences would only affect one format, and in one way only. So I'd rule that factor out. As for exposure times, I always use a clock as reference for seconds (which corresponds to a metronome beat of 60 ;) ).

Diane, various subjects, stopped down in various ways, sometimes also wide open. There isn't *one* way I shoot, and that variation reflects on all formats - it's just the 8x10s that get systematically underexposed...

[ic-racer]

Fomapan 100, …

How are you determining your exposure index? When you do your 'zone 1 test' try to use a shutter-speed and aperture that would be similar to actual shooting conditions.

That film has poor reciprocity. By sensitometer (Wejex; 1 sec exposure) it is already one-stop slower than T-max 100.

[Bruce Watson]

I don't think I am hitting reciprocity issues with 1/2 sec exposures…

And yet, you could well be. Reciprocity failure isn't really shutter speed related although shutter speed makes a decent warning flag for it. Reciprocity failure is about getting enough photons to breach the exposure threshold. The shutter speed is valid for the entire sheet of film, but the actual exposure to photons varies markedly across the film. So... the shadow areas of the film go into reciprocity failure well before the mid-tones and highlights.

I'm just saying that the combination of a 1/2 second shutter speed and a poor reciprocity failure film stock makes it likely that at least some parts of your film are in reciprocity failure.

But... that's probably not your main problem. If your film comes out "looking thin" it's because your highlight density is low. If you are working in 10x8 so that all things are equal (or as good as you can make it) with your 5x4 work, it's probably a change in sensitivity from batch to batch of your film. Easy enough to check. Cut up one of the 10x8 sheets into four sheets of 5x4, and load them into one side of four different film holders. Load the other side with the film you know works well for you. Then go into the field and setup on some scenes -- expose both sides of the film holder identically. If both look the same after processing, it's not your film or processing, it's something else. But if they don't look the same after going through the same process, it's almost certainly your film.

Personally, if I were shooting 10x8, I'd only be using films with excellent reciprocity failure characteristics. More expensive, yes. But a pittance compared to the time and effort of carting that equipment around and time and effort of making a setup on a scene. Especially if there was much travel involved. So Foma for the backyard, yes. But for a trip to Yosemite, it's TMY-2 all the way for me. Of course, YMMV.

[csant]

ic-racer, I haven't done much specific testing, assuming things would basically work the same as I have gotten used to on 4x5 and 5x7. But obviously I need to reconsider that...

Bruce, thanks for that detailed explanation. What I understand is that on 8x10 reciprocity might be much more pronounced than on smaller formats - that is interesting... I am having some suspicion on something like that, but it felt like rather improbable... Because it would mean that thinking exposure on large large format is different than on smaller (large) formats. I am planning on carrying out some tests the way you suggested, and see what comes out of that.

[Brian Ellis]

I doubt that reciprocity failure is the cause of your problem with 1/2 second exposures. It's theoreticallly possible but even if it exists the extent of the underexposure would likely be so small that you wouldn't notice it.

Bellows extension conceivably could be a problem if you're doing a lot of closeups. As a general proposition, you don't need to make any adjustment for bellows extension as long as the object on which you're focusing isn't closer than 8 times the focal length of the lens you're using (some people say 10 times, either is probably close enough). If you've been photographing things closer than that it's possible that you haven't been properly adjusting your 8x10 exposure times, though this seems relatively unlikely since it hasn't been a problem with smaller formats.

You perhaps already know this but just in case, to determine whether a problem is with exposure or development, look carefully at your negatives, preferably on a light box if you have one. Look closely at the shadow areas, i.e. the thinner areas of the film. Do you have the kind of detail and texture there that you would like or are those areas pretty much just blank film (i.e will print as a solid black blobs). If so then your problem is exposure. Then look at the brighter highlights on the film. Do they have the kind of texture and detail you want or are they so dense that it's unlikely any light will get through them when you print (i.e. they'll show up pretty much as paper white)? If so then the problem is in your development.

Since you're using the same lens on 5x7 and 8x10, and since you say your exposure and development methods are the same with both formats, I'd have to guess that either there's something wrong with your 8x10 camera (though I can't think of anything with a camera per se that could consistently lead to underexposed negatives) or you got a batch of 8x10 film that doesn't have its rated ISO.

As an irrelevant aside, I'd be surprised if any human being can remove a lens cap and put it back on in a tenth of a second or even half a second as opposed to a quarter of a second. As a musician you may intuitively know what a tenth of a second "feels" like but I don't think you can physically get the cap on and off in that time and that precisely. I realize you do the same thing with the same lenses when using smaller formats so this presumably isn't the source of your problem, it's just an observation. And of course I could be wrong, I've never used the lens cap method myself with anything close to exposure times that short.

[Martin Miksch]

... I'd be surprised if any human being can remove a lens cap and put it back on in a tenth of a second....

Me too,

just look for a Sinar -
or if you want to do it by hand- a Packard shutter.
Regards
Martin

[AJ Edmondson]

Have you looked at the volume of developer? Even if the dilution is the same you will (in theory at least) require four times the volume of developer (compared to 4x5) to attain the same level of activity. For those who use "one-shot" development this may be of greater consequence because of the tendency to minimize the volume used for each sheet. Kodak formerly published minimum amounts of developer stock solution for film size - I don't think they currently publish this (I maybe wrong on this) but it was very useful. Hope you find the source of the problem!

[csant]

Hmm, the volume of developer is something I should actually be more careful with… I doubt that it is at fault in this case, though: I have managed to develop without problem 6 sheets of 5x7 in the same volume I used for 2 8x10 sheets, and that should cover it… But thanks for the hint!

As for manual "shutter" speeds: you'll be surprised with what precision a professional musician can control and coordinate speeds up to 1/8 sec ;) Seriously, that'd be a demisemiquaver (or thirty-second note) at 60 for the crotchet (or quarter note), which isn't too difficult… I actually don't remove a cap, that'd be way too much movement for the hand: I use a darkslide in front of the lens, lift it up and down again (aka "Jim Galli shutter"). For higher speeds you'll better use two darkslides, but it also needs a lot more exercise :p

The times I generally use though are way more relaxed than that, generally longer than 1/5… Just set your metronome to 60, that'll give you a beat each second. Then repeat with me "I want an ice cream"* and have the "I" be on each beat: when you reach "want", 1/5 of a second has passed. Thus: open shutter on "I", close it on "want". With a bit of exercise you'll see how simple this is :)

* There are more precise wordings you can use, it's just the first that came to my mind.

[rdenney]

Don't underestimate the need to consider bellows extensions.

Think of it this way: A full-face portrait with a 35mm camera requires an image size of an inch--about a tenth the size of the face. There's your magnification factor of 1:10. The distance to the subject would need to be ten times the focal length to achieve that magnification.

So, a full-face portrait with any larger format will require magnification greater than 1:10. With 4x5, a four-inch face on the film would need a magnification of about 1:2.5--the image is about 40% of real life. With 8x10, an 8" face is just a little short of 1:1 and nearly in the macro range. At 1:1, the lens will require twice the bellows draw and therefore a two-stop adjustment (4x bellows factor). It is not hard at all to get into the near macro range with 8x10.

A head-and-shoulder portrait might require representing two feet of the the subject on 8 inches of film--about 1:3. The rule of thumb that bellows draw isn't a factor when the subject distance is 8 times the focal length or more is an easy line to cross.

Rick "who might someday have a hankering for a Sinar film-plane spot meter to make this easier to deal with" Denney

[csant]

Hmm, Rick, thanks for that. Something along that line is what I was having suspicions about - but couldn't really explain it (even though it really is rather simple, isn't it?). Makes perfect sense, and I'll be much more careful with "it is not hard at all to get into the near macro range with 8x10". :)