How much to push/pull

[Sorin Varzaru]

When I was reading on sheet processing I found out the the best way to "bracked" is to take two exposures, process one, see how it looks and then process the se cond with push/pull to get a "perfect" exposure. All this sounds good, I did tha t, but the question is, how do you know how much to push or pull. Let say the first sheet is slightly too dark. I obviously want to push. How much? Can u se use my spot meter somehow to meter the slide on the light box? For example, assuming I have a building in the shot and I want the wall A (dark) to look like wall B (not so dark), could I just meter both walls and push the processing wit h the difference?

[Sorin Varzaru]

I appologise, I should've been more specific. I shoot color slide film exclusivly.

[Dave Mueller]

I think the E6 process does not allow this kind of flexibility. Most of these ideas are strictly for b&w film (Zone System N+1, N-2 etc). They're not push/pull in the normal sense (ie a whole stop like ASA400 to 800), but are minor adjustments to developing times to compress or expand the contrast range of the negative. I know you can push or pull E6 film, as most pro labs will do it (for an extra charge). Check the data sheet for the film.

[Dave Mueller]

Your English is fine, I re-read your question, I did not read it correctly (my fault, not yours). Unfortunately, I think the answer is experience. The only way to develop a way to measure what you want is to run a series of tests where you change the development in small amounts (maybe 5 or 10%) and record the density changes. If E6 behaves like B&W, you'll need to have frames with several values on each one, since the shadows don't expand as much as highlights, and highlights don't compress as much as shadows.

[QT Luong]

It also seems that with your suggested method the readings would be dependent on the brightess of your lightbox, not to mention problems due to its possibly non-uniform illumination. It's surprising how much of that is compensated by the brain. I measured a difference of 2 fstops across my Logan, yet to the eye it looks sort of OK.

[Sorin Varzaru]

Tuan, shouldn't the difference between the area be independent of the light intensity ? Assuming of course the light is constant across the light table. And if it's not, I guess I could move the sheet to measure above the same area or the lt.

[kthompson]

Sorin, are you running this film yourself, or are you using a lab? This is important because, as was stated above, your light box intensity/color balance is going to have to match up with whatever your lab's viewing area is as well. So, yes, it probably would be best to ask for their advice as to how much to push. I work in an in-house studio and we run our own E6, so yeah it's possible to push/pull in tiny increments to either tweak your exposures, contrast, or maybe use it to "clean" up highlights. You can get by with pushing E6 better than pulling, although you can reduce contrast this way. It's just that as you do this, you also effect color balance, so it can get tricky if you're after correct color. Light tables for correct viewing (like in a pro lab) are rated for CRI (color rendering index) this is alot different than just any light box, so what may look good on yours, may look lousy at the lab. I have worked in studios in the past, that did this sort of shooting all the time, but we usually try to center all our exposures around what's normal for us, and use a std. 1st dev. time. You can really fine tune it though, like 15 sec. extra might be all you need. Maybe use the highlights as your guide first, because if you push too far, they're going to be the first to go. If you're running your own E6, I might be able to get together some times for you. I've found that it's just more predictable to learn to use polaroid and base your exposures off that (judging highlights). I just reread your original post. I think the answer to your hypothetical bldg. shot is "no" (short answer). Because trans. only hold like 5 stops, so you might want to shoot on an overcast day, or expose for the lighter wall, and use a massive amount of fill for the shaded one. If you pushed your film, you might end up blowing out your highlights. Maybe someone could suggest the merits of pre-exposure as well. Oh well, sorry for the length, good luck..

[heidis]

Sorin,

A good suggestion that has been made is that you need to learn (by your own experience and eyesight) what the differences in exposure will look like on E6. I'd like to suggest a way of learning this that will eliminate guesswork once you've learned what to look for. You can do this on a smaller format such as 35mm to save film costs. A longer series of test subjects will help you see the differences...

Try shooting a subject via your normal metering method. Let's say that you consider it mid-tone. Then bracket a half stop each way, and a full stop each way. You might even go further if you like. Then do the same thing with a light-toned subject, such as a snow-covered field, and bracket the same way. Finally, do the same with a darker than normal subject. You can expand this by covering a range of differently colored subjects too. It's not important whether your subject is a particular tone for this test, but you will easily be able to see the difference that various exposures make. For example, if your first exposure looks about a stop too dark compared to what you had in mind, you'll know to push the second exposure by a stop. Keep careful notes, and examine the results. Make sure that you can see each entire series at the same time, with the same illumination.

You should get a good idea of a half-stop from "ideal", a full stop from "ideal", and so on. This is basically the way that I learned how to spotmeter, and how to compensate accurately when metering a non- midtone subject. Good luck! Your English is very good, by the way

[Sorin Varzaru]

Thank you for all the advice you've given. For the record, I am shooting 8x10 color slide so I kind of have to keep the testing down due to the cost involved. I also do my own processing. Since I've started 8x10 a few weeks ago I only shot 7 pictures (14 exposures) and so far all my exposures were exactly as expected (no need for any of the above). That is probably due to the fact that handling a camera of this size really makes you measure twice before you "cut" :- ). I'm still working on my focusing though. I've managed to get the focus plane in the most bizare positions :-).

[Bruce M. Herman]

Sorin,

I frequently ask my lab to push or pull Velvia and Ektachrome (E100S, E100SW, and so far only a little E100VS). Here are some of the things that I would suggest.

1. Don't worry about calibrating your light table and theirs. However, you must be consistent in your use. So always use your light table (assuming that you have a decent model), and change its bulbs before they get to the end of their lifespan. I think that my Graphic Light bulbs are rated for 3500 hours, but your brand may be different. Also try to consistently view your transparenies in the center of your light table when considering exposure.

2. You must always use the same lab, and they must run a carefully calibrated processing system. If your lab doesn't serve professionals, you may not achieve satisfactory results. I say "may not" because even some amateurs have sufficiently good technique to do this well.

3. I have used a spot meter to give me a starting point for estimating the correction. But I usually make 3 transparenies in situations in which I am unsure of the exposure or too rushed to be careful (i.e., light is fading). At any rate, make your reading on something close to mid-tone color. Having said this, I think that you'll also discover that two different exposures of the same subject may both be acceptable. This is particularly true of sunsets. Experience will improve your results.

4. I have pushed all of the above films up to 2 stops and pulled them up to 1 stop when I really wanted to see the image. These are extreme situations, and they don't always work out well. But sometimes I get usable results.

3. Finally, don't throw away the slightly under- or over-exposed images. They can be scanned for printing after correction in a photo-editing package. Or you can use them as the basis for making 70 mm duplicates for clients, thus saving your best originals for those who really want a 4x5 transparency.

By the way, I learned this procedure from Pat O'Hara several years ago.

Best wishes, Bruce