Varying the ISO


davetac Plus
10 69 2 United Kingdom
29 Aug 2019 11:12PM
If I am using Ilford HP5 400 film, if I set the camera to ISO 100 and sett either the aperture or shutter speed to + 2 stops will I get better or worse results as regards grain and contrast etc?

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altitude50 15 16.3k United Kingdom
29 Aug 2019 11:32PM
Depends what camera you are using. Are you resetting an automatic function or just the film reminder dial? More information needed.
davetac Plus
10 69 2 United Kingdom
30 Aug 2019 12:05AM

Quote:Depends what camera you are using. Are you resetting an automatic function or just the film reminder dial? More information needed.
I don't get the film reminder dial remark. My Olympus OM 30 can be set from50-1600 ASA I believe. I'm using ASA 400 Ilford HP5 and fully manual but I've seen posts mentioning that they have "pushed to 800 or pulled to 200 or even 100." I assume that means perhaps underexposing by a couple of stops and then pushing during development but find it confusing to say the least. Say I set the indicator to 800 (fast) do I then shoot at f16 instead of f8 while maintaining shutter speed in order to compensate? To what purpose? Or am I completely confusing myself?
30 Aug 2019 12:06AM
You'll get images that are over exposed by 4 stops.
davetac Plus
10 69 2 United Kingdom
30 Aug 2019 12:24AM

Quote:Depends what camera you are using. Are you resetting an automatic function or just the film reminder dial? More information needed.
That's what's confusing me. The film is an unalterable ASA 400, I set the camera up accordingly and using say f8 the exposure meter might say1/200.
But if I mistakenly (or otherwise) set the ASA to 800 (1 stop) the exposure meter would wrongly point me to 1/400 when in fact since the film is still the same I should shoot at 1/100?
davetac Plus
10 69 2 United Kingdom
30 Aug 2019 12:28AM

Quote:You'll get images that are over exposed by 4 stop
I think I'm misunderstanding what others are writing. They are developing their films themselves perhaps and pushing or pulling in the development stage. So I'll stick to setting the ASA according to the film speed.
altitude50 15 16.3k United Kingdom
30 Aug 2019 8:17AM

Quote:Are you resetting an automatic function or just the film reminder dial?


With no information about the type of camera used, the OP might have been using a manual 1950's camera for example with no built-in auto exposure, how were we to know?

davetac Plus
10 69 2 United Kingdom
30 Aug 2019 8:34AM

Quote:With no information about the type of camera used, the OP might have been using a manual 1950's camera for example with no built-in auto exposure, how were we to know?/quote]


Thanks I appreciate my question was possibly confusing. I guess what I meant is if the dial is set to true 400 and aperture is let's say f8 and the exposure meter specifies 1/200 then I move the dial to 800. Does the exposure meter then give a false reading of 1/400 and I should halve it to 1/200 regardless. Sorry to be so vague previously.

sausage Plus
15 606 United Kingdom
30 Aug 2019 9:28AM
Set the camera for the film ASA. You only need to push developing if for some reason you made a mistake in shooting (underexposed for instance or darker than you could get a proper exposure for) and realised when you got home.
dark_lord Plus
15 2.3k 598 England
30 Aug 2019 10:30AM
Use the film at its normal rating.
If you shoot at 800, which is one stop higher, set the exposure according to that speed. You then compensate for that when you develop the film. If yu send it awa let the lab know. There's often an additional charge.

Pushing will result in increased contrast. But, contrast can be easily increased in software if scanning the negs or by printing on contrasty conventional photopaper.
Unless you need the extra speed (very low light, need to capture action, for example) there's no need to adjust the ISO.
davetac Plus
10 69 2 United Kingdom
30 Aug 2019 10:37AM



Pushing will result in increased contrast. But, contrast can be easily increased in software if scanning the negs or by printing on contrasty conventional photopaper.
Unless you need the extra speed (very low light, need to capture action, for example) there's no need to adjust the ISO.


Thanks Guru, that's cleared it up nicely. Developing at home is a whole different ball game which I'd like to try but I don't think my marriage would survive my locking myself in a dark room or having a rumble in a black bag. Maybe in my next life GrinGrinGrin
davetac Plus
10 69 2 United Kingdom
30 Aug 2019 10:38AM

Quote:Use the film at its normal rating.
If you shoot at 800, which is one stop higher, set the exposure according to that speed. You then compensate for that when you develop the film. If yu send it awa let the lab know. There's often an additional charge.

Pushing will result in increased contrast. But, contrast can be easily increased in software if scanning the negs or by printing on contrasty conventional photopaper.
Unless you need the extra speed (very low light, need to capture action, for example) there's no need to adjust the ISO.

30 Aug 2019 11:09AM
When you set the ISO you are telling the built-in light meter how sensitive the film is, and the meter will calculate the "correct" exposure accordingly. If it's an ISO400 film, and you lie to the meter, telling it you've loaded an ISO800 film, the meter will believe you ( because it isn't very intelligent and will believe anything you tell it ) and will therefore calculate exposure based on that. The resulting image will be underexposed by one stop.
pablophotographer 8 1.3k 353
30 Aug 2019 10:20PM
You can not "push" a couple of frames and "pull" some other frames of the same canister. If you decide to "push" or "pull" the film you would have to do it for all the frames, all 24 or all 36 of them. That is because you will develop all the roll together. Sounds you should go for the F P4, ISO125 film which can be pushed up to ISO6400.

Check this out:

https://emulsive.org/reviews/film-reviews/ilford-film-reviews/ilford-fp4-plus-35mm-120-format-and-sheet-film


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