rating film at a slower speed

[Disaster_Area]

I've become pretty familiar with rating films at higher speeds than box, but I might be a bit confused when it comes to rating a speed slower. Is this different than pulling? When I push a film, I rate it at a higher speed, but I adjust development time, and from what I can tell, pulling is the same. One rates the film slower but again adjusts development time to compensate. As an example, when someone says they rate Agfa APX400 as 250 instead, are they pulling the film a little less than a stop and adjusting dev time, or are they shooting at 250 but developing like it was still 400 ISO?

 

[st3ph3nm]

I haven't tried developing myself, yet, but I can tell you that Kodak's C41 B&W comes out a whole lot nicer if you rate it a bit slower than than the listed 400. IOW, you're setting the camera to "overexpose" by however much - in my case, about 250-300. The results are sho clearer shadows, and less grain.

 

[bmattock]

I understand how you could become confused, but think it through. If you rate it at EI 250 and then process as if you had rated it at box speed, you will have effectively overexposed (or overprocessed, take your pick) the film.

Pushing is underexposing and overprocessing to reach (hopefully) correct exposure. Pulling is overexposing and underprocessing for the same desired result.

Pushing and pulling are the same in the sense that you adjust development time and/or developer dilution. Just as some films are better for pushing than others, some react better to pulling than others.

 

[Nh3]

this should help you. http://www3.telus.net/drkrm/push-pull.htm

 

[Sanders McNew]

this should help you. http://www3.telus.net/drkrm/push-pull.htm

Beware of misleading information at that page.
For example, it offers a "rule of thumb" to
adjust processing times by 2 minutes per stop
of under- or overexposure. That might be too
much for high-concentrate developers (e.g.,
HC110 dil. B) and too little for weaker mixes
(e.g., Rodinal 1:100).

Your question is vague. Some people shoot
below box speed because their light conditions
demand it, given their shutter and aperture
requirements. Then you might want to reduce
development time to compensate. Others
(myself included) shoot below box speed to
increase exposure and gain detail in the
shadows. If that is your intent, then you
want to process the film with a box-speed
recipe -- pulling would defeat the purpose
of overexposure.

As a rule, you will find that most B+W films
are very tolerant of overexposure, and very
forgiving of variations in development -- at
least that is my experience with Tri-X and
Foma films. So long as you get enough light
on the film, you should get a printable negative.

Sanders

 

[charjohncarter]

I shoot below the rated speed because I want as much shadow detail as I can get. I can always increase contrast later. And it is very hard to get shadows out of underexposed images.

As for developing, I experiment until I get the time that I need. It may be the recommended time or it may be longer or shorter depending on the film.

Here is one that I did to really get lots of shadow detail, it was a low contrast scene, but it still has every shade in it:

 

[Al Kaplan]

Exposure is the best way to contol density. Development controls contrast, and to a lesser extent density. Density of course is what controls effective film speed. If you don't give enough exposure you'll have featurless shadows, while too much exposure will block up your highlights. You want to pick a developer and developing time that'll give you a good print on grade 2 or 3 paper. You have a bit of experimenting to do before you'll zero in on what works best for you. Other variables include the accuracy of your thermometer, your particular agitation regiman, and the ph of your water. Have fun. You'll get there!

Don't make the typical beginners mistake of wanting to try every film and every developer on the market in hopes of finding the "perfect" combination. Start with ONE film and ONE developer. Tri-X and D-76 diluted 1:1 is a good starting point, tried, true, and tested combination. Then REALLY learn what it will do before trying anything else. There's an old saying that the worse your negatives are the better the printer you'll become. There's a lot of truth to that, but good negatives are easy to achieve and a joy to print.

 

[venchka]

Best Rule of Thumb:

Expose for the shadows. Develop for the highlights.

If you don't give the shadows enough exposure, you'll never get good shadow definition no matter how long you develop.

You want to develop for just enough time and agititaion to keep the brightest highlights from loosing all detail.

It's easy to find out what ISO setting you should use for a given camera/meter/film/developer combination. That test determines your personal film speed. Then test to find out how long you need to develop to keep the highlights from blowing out.

In my case, I expose HP5+ at E.I. 250 and develop in Xtol 1:3 for 9 minutes with continuous agitation. Kodak says the time should be 12:15 minutes. I started there and then reduced the time until I got the results I wanted.

I have also exposed HP5+ at 1600 and developed in Xtol 1:3 for 15 minutes with good results. Lots of ways to skin that cat.

 

[Svitantti]

I agree totally with what Al Kaplan said about testing different films. I did that "mistake" and it was all a waste of time. Just pick one nice film (Tri-x or HP5+... or Tmax if you're allergic to grain) and D-76 or maybe X-tol or HC-110 and learn to use them.

"Learning" to use one combo helps you understand the main points of exposure and developing a lot better than testing different film types, one each or so.

Also this thumb rule of "Expose for the shadows. Develop for the highlights" is good to think through.

Developing will not get you much more shadow details, but it can develop mid-grays up to white (pushing) to give you contrast and highlights that would have been missing with less development. The shadow detail comes from exposure.
On the other hand it is good to develop the negative so much that you get your mid-grays and whites where you wanted them.

People measure light in different ways and that makes them rate films differently. Some say the same film works 320 or 200 ASA when some use it 400 or even 800 with great results. The meter, metering, maybe also the shutter makes easily these differences.

Not a bad idea to test your exposure metering and development by shooting a test roll and developing parts of it with different times to find out the best combo. I've had no patience to do this so far though.

I just try to meter so that I expose enough and then try to compensate possible over- and underexposures when developing.

Heres a good PDF some might be interested in:
http://www.robgray.com/giftshop/freestuff/pdf/exp_cont.pdf

 

[Roger Hicks]

Lots of ways to skin that cat.

Very true.

Loath as I am to disagree with Al, I'd add: be as promiscuous as possible with film at first until you find one combination that's 'magic' for you. Otherwise you run the risk of trying to start out with a combination that may be 'magic' for someone else but not for you. If I'd settled on Acros, for example, I'd have given up. When you find the 'magic' film, that's the one to concentrate on. The likelihood of HP5 or Tri-X not 'working' for you is slender, but not negligible.

By all means choose a single mainstream developer -- I'd back DD-X (for speed and convenience) or one-shot 1+3 D76/ID11 -- or you'll be changing two variables at a time. Avoid faddish developers that may be raucously recommended by a handful of people: ask yourself why there is only a handful of them.

For a fuller understanding of film speed, see:

http://www.rogerandfrances.com/photoschool/ps iso speeds.html

Note that film speeds were based on 'focus groups' that did not necessarily contain many experienced photographers, and the original research was conducted with 5x7 inch contact prints. Even so, the Kodak/ASA/ISO system is still the best we've got.

All film speeds are a compromise, in any case. A bit more exposure than the ISO speed gives tonality that most people like more, at least with wet printing, but it also gives lower sharpness and (with B+W) larger grain. As for the risk of 'blowing' highlights with B+W negative films, you have to overexpose wildly -- at least 2 stops, maybe 3 or 4 depending on the film -- before it's a problem with wet printing, though scanners may not be able to see through the high densities caused by overexposure.

Cheers,

Roger

 

[Svitantti]

Overexposure with b&w negatives shouldn't be a problem with (film) scanners usually. With dark slides the densitys are much bigger and that is where the problems start. Talking about 3.8D with slides and I guess maximum 2.0D or so with negatives. Flatbeds might have some problems even with those though...

Also I quite don't get it - how would more exposure make the grain bigger? Doesn't that happen with underexposure and pushing?