View Full Version : Stupid questions about exposing B&W film
Once again, I will be asking a silly question, but once again bear in mind I'm from the digital world and am very curious to learn.
I know with traditional colour negative and chromogenic b&w film that I can over or under-expose shots by about a stop each way without any problems in development. More to the point, from the processor's point of view, unless I specifically request a push process, the development time period remains the same.
What I'm trying to find out is whether this process holds true for traditional black and white film. Using a roll of say, Neopan 400, can I shoot some shots at ISO 200, 400 and 800 and then hand over the roll to a lab and get them to develop it at the 'standard' time (ISO 400?) without encountering major image quality issues? I am aware that b&w film can be easily pushed/pulled during development, but I am wondering how tolerant it is to varying ISO/exposure levels in the same roll.
Yours in ignorance and gratitude,
B/W film has a lot of latitude, more than color. However, it is always best to expose film at its proper ASA/ISO, and have it developed normally. That said, some people do use different ISO's for special effects if that is what you had in mind. Some also insist that ISO ratings are usually over, and rate their film 2/3 to 1/2 less.
I know that just sounds confusing. I would suggest you do some experimentation. You shutter speeds could be off enough to make a difference on one end but not the other.
short answer is no, not on the same roll.
longer answer...you need someone more technical than i.
It's true that films have latitude, but the quality of the image gets affected (decreases) while you cheat the correct exposure.
To get good exposures you must learn to know your camera and your meter, you have to examine your negs and learn from your exposures.
Some from this experience get EI (Exposure Index) for the favorite film they shoot. That is why some shoot Trix at 320 or 200.
You must find your own style or learn how the film reacts to different light situations, and this is something the good photographers get to know trough time.
for black& white silver based film It is the developer/film combination that ultimately determines ISO, also the lens contrast to some extent. The manufacturers put ISO ratings on the film, but those are only correct when you process in specific developers at specific times and temperatures, and can be effected by the water you use to mix up developer, and your agitation technique while developing.
It is best to shoot tests, develop and then adjust your personal ISO rating for a particular film, based on your evaluation of the developed, fixed, washed and dried negatives.
As a general rule you will get satisfactory results using the manufacturers ISO, if you develop in the manufacturers recommended developer for the manufacturers recommended time and temperature.
B+W film has some latitiude in exposure. It is much more tolerant of over exposure than it is of under exposure.
Which is why many people will rate your example of Neopan 400 at 320 but get it developed at 400. OTOH, you can do the 200, 400 and 800 trick in one roll with a chromogenic like Ilford XP2. The overexposed end (200) comes out better in terms of image quality but it can be done.
Not a silly question Hin, but a very reasonable one especially if you have some digital experience.
I often shoot b&w without a meter, going by some variation of the Sunny 16 rule, which gets troublesome around the late afternoon, when light starts changing rapidly. I usually cheat towards the over-exposure side, but I find that since I'm scanning my film most of the time, I can get away with almost 2 stops under-exposed sometimes.
Thanks for all that info guys. It looks like my cunning plan to shoot silver b&w in the extreme variable light that is the London 'spring' might have to wait till I have either more camera bodies, a great willingness to burn through film or perhaps, maybe just perhaps, a camera with a very low shutter speed (that's a justifiable reason to buy a new camera, isn't it? Isn't it?).
i use BW film and do my own processing,and i always try to shoot at the closest ISO as per film....however,push/pull process goes better on BW than colour!Sometimes i do shoot some frames at a different ISO than the film has,but the more distance between the original ISO and the latitude of your "cheat"shot...ugly things start to happen:-))
first of all,GRAINS!Big,nasty and not at all workable in whatever PS used!Lupms are getting nastier the more you go upwards from your original ISO...
however,the best push/pull process i had was, as follows:
Film: ILFORD FP4+,rated at true ISO 125
Shots in question:10x50asa...10x125asa...10x400...4x800
Developer:KODAK D-76 conc.1+4
1.The 50/125/400 was ok...more than ok the 400 asa(still some lumping,but printable)
2.At 800...NOTHING...lost all images !!!!!!
It seems that it does very much to do with the DEVELOPER you are using(see fine/medium grain developer,time and way of process/temp,etc),and perhaps more important,THE DILUTION(concentration of your stock!)But as i am not a pro in my darkroom,i just guess...this IS a guestimate problem,ain't it?
hope it helps
You don't need more camera bodies -- you just need to understand what sort of light is falling on your subject. One option is to get yourself a small hand-held incident light meter (the kind with the white dome over the sensor - I like the Gossen Digisix). As long as the dome is in the same kind of light as your subject when you take a reading (i.e. pointed in the same direction as your subject with respect to the light source) you will be given a range of shutter speeds and f-stops. With an f2 lens and a roll of 400 BW speed film you should have all of the flexibility you need.
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