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Kyler.

Changing ISO Speed in the Middle of a Roll

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Hi everybody,

I have recently got into film so I apologize if my question sounds silly.

I have learned that you can push ISO speeds on films and still get good results.

A lot of times people push an ISO 400 film to 1600.

I am wondering what happens if you change the ISO speed of a film in the middle of a roll?

Let's say your shooting a 400 speed film and halfway through you go to a darker environment. Will there be any bad effect to bumping the ISO to 1600 mid-way through the roll?

 

Thanks,

KYle

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When developing your film, you have to develop it for a certain ISO value.

Switching ISO in the middle of a roll will result in either over- or underexposed pictures.

So unfortunately, you can't just switch ISO values as with a digital cam.

 

Rgds

Ulev

 

 

Hi everybody,

I have recently got into film so I apologize if my question sounds silly.

I have learned that you can push ISO speeds on films and still get good results.

A lot of times people push an ISO 400 film to 1600.

I am wondering what happens if you change the ISO speed of a film in the middle of a roll?

Let's say your shooting a 400 speed film and halfway through you go to a darker environment. Will there be any bad effect to bumping the ISO to 1600 mid-way through the roll?

 

Thanks,

KYle

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Hi

 

You can change ISO if you use a dye image film lke Ilford XP2 or the Kodak or Fuji equivalents.

 

But just like a M8 or M9 if you use large walues like 1600 you lose some quality, and it is more difficult to get a nice print. But the option is there 200 to 1600 or more...

 

Noel

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With an ordinary single-bath developer you might think of it this way - you have an ISO 400 film, and you have a developer that correctly develops ISO 400 films that have been exposed at ISO 400 when used for the proper time at the proper temperature etc. The images taken when you set the ISO dial to 1600 will look two stops under-exposed. No way around that. Now it might not matter as much as you might think, as B&W film is fairly forgiving about exposure - you will probably make acceptable prints from the under-exposed images, even if they won't be technically perfect. If you shoot the whole roll at a different ISO than that indicated on the film box, then you can alter the development time to allow for this, but some shots at one speed and some at another are going to require different development times to be their best, and given that a the whole roll is developed in one go you can see there will be a problem.

 

A two part compensating developer like Diafine will cope happily with this kind of thing (as it develops films independent of ISO, time and temperature), but there is still no no point in changing the ISO setting on your camera to kid yourself that you just exposed a frame correctly.

 

In either case, what was the point in changing the ISO? It simply let you under-expose by two stops whilst the meter said it was OK to do so. Better to leave the ISO dial alone and know that you are choosing to under-expose, even if only because you might forget to change it back for the rest of the roll.

 

Chris

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+1 to everything that has been said here so far.

 

The the ability to salvage the frames of film shot at a different ISO will depend somewhat on the type of film -- some have better exposure latitude than others. But in general, traditional B&W film is fairly forgiving to exposure errors and you may find that you are able to use much of what was shot. If it was me, I might try processing it for one-stop under rather than 400 or 1600. That way you may have a chance at a more consistent result across the entire roll.

 

This may be a good time to look at a second body to load the higher speed film in!

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You can change ISO if you use a dye image film lke Ilford XP2 or the Kodak or Fuji equivalents.

 

That's changing the EI, not the ISO speed.

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I'm doing this regularely with Tri-X 400 in Diafine. EI 400-1600 and sometimes 400-2000 on the same roll of film is okay. As I work with a M3 and M2 and measure with a Digiflash, I just count +1 or +2 EV from 400.

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Rewind the film and load a faster film. If economy is important, then do not wind the tongue into the cassette, note the frame number and mark the cassette, then later load it again at 2 frames beyond last frame.

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Don't do it! One of the big advantages of digital. But how many times do you really need to change ISO anyway? With fast lenses you can get away with even ISO 100 in pretty low light.

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I'm doing this regularely with Tri-X 400 in Diafine. EI 400-1600 and sometimes 400-2000 on the same roll of film is okay. [...]

 

When I read or hear such claims I want to see outcomes and learn the expectations of the photographer. Clearly, your concerns are not in the zone system camp, and that is just fine. You might evince the responsive character of the 35mm photographer who gets what he can, and when he can, from the miniature format; I've also known total slob photographers who make the same claim.

 

Got pictures?

Edited by pico

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Hi everybody,

I have recently got into film so I apologize if my question sounds silly.

I have learned that you can push ISO speeds on films and still get good results.

A lot of times people push an ISO 400 film to 1600.

I am wondering what happens if you change the ISO speed of a film in the middle of a roll?

Let's say your shooting a 400 speed film and halfway through you go to a darker environment. Will there be any bad effect to bumping the ISO to 1600 mid-way through the roll?

 

Thanks,

KYle

 

Kyle,

 

All films have an intrinsic ISO. You cannot change that. If you "change" your ISO from 400 to 1600, you are in fact under exposing by 2 stops. There will be no effect on the film, except that you will have some frames that are thin to very thin, and the thinner they are, the more they will be unprintable or unscanable.

 

Figure out what your film speed is (it may not be what is written on the box), and try to make technically good negatives. Once you can do that reliably, then you can get on with the important work of figuring out where to point the camera. There is the real challenge.

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All films have an intrinsic ISO. You cannot change that. [...]

 

Here are a couple of links to a good authority affirming what Michael wrote: Beyond Monochrome and darkroom magic.

 

I highly recommend the book, Way Beyond Monochrome.

 

Digital mavens will never understand this stuff.

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All films have an intrinsic ISO. You cannot change that.

 

I'm not happy talking about "intrinsic ISO" because measuring the ISO speed of a film includes developing it in a particular way and changing the development could result in a different "ISO" number. But each film does indeed have an intrinsic sensitivity or speed that can't be changed.

 

You can, however, change the way the film responds to light by changing the way you develop it - and if you do so you will need to set a different ISO number on the exposure meter (or camera) to get the same density on the exposed and processed film. The proper term for the number you set on the exposure meter is "Exposure Index" (EI); terms such as "ISO" and "ISO speed" ought to be reserved for the intrinsic speed of the film as measured according to the relevant ISO standard.

 

What you can't do is set different exposure indexes for different frames on the same roll of film and expect the film to know the difference.

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That's changing the EI, not the ISO speed.

Hi girdano

 

Perfectly true, but abstract, the EI 'speed value' recomended by Ilford is not to the ISO standard so Ilford have not provided an ISO EI...

 

recommend reading.

 

http://www.ilfordphoto.com/Webfiles/20061301945161573.pdf

 

Printing can be more difficult if you threat the film as though it had a higher ISO, i.e. using a larger EI, but it is not like the difference you get uprating (changing the EI) of a silver image film.

 

Noel

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Hi Noel,

 

The Ilford data sheet says "XP2 SUPER film has a speed rating of ISO 400/27°" and then recommends exposure indexes of anywhere from 50 to 800 depending on circumstances, all with standard C41 processing. That sounds like an ISO speed to me.

 

Obviously the ISO procedure for rating conventional B&W films doesn't apply to chromogenic ones.So far I haven't heard about an ISO procedure for chromogenic B&W, so I guess Ilford used the procedure for C41 colour films. Is that why you say Ilford's ISO 400 "is not to the ISO standard"?

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Hi John

 

I have the horrible impression we may be agreeing with one another.

 

It is not me who says that Ilford is not using the ISO standard, but Ilford, in the link I provided. Ilford say 400 is merely a`practical or 'optimal' setting, for normal C41 processing. I'm sure you could use the ISO standard, but it might confuse.

 

You can alter the processing and some people tried XP1 (an age ago) at 10000, but Ilford suggest the range 200-800, same lnk.

 

Noel

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To make technically high quality pictures, the important question is "What speed rating do I set on my meter"?

 

For XP2 (normal C41 development), my answer is 200. This produces a density of .1 when the film receives a Zone I level of light, i.e. what the meter says, then closed down by 4 stops. Any other speed setting produces Zone I that is either to dense or too thin. Ilford says that XP2 can be rated at anything from 50 to 800, but in my experience the quality (i.e. printability and scanability) drops off when the film is rated at something other than 200.

 

Knowing how Ilford determines its published information is not very useful when setting your aperture and shutter speed.

 

Make tests and find out the facts.

Edited by Michael Hiles

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To make technically high quality pictures, the important question is "What speed rating do I set on my meter"?

 

Make tests and find out the facts.

 

Just three comments

 

- sophists normally put a false statement in their 1st sentence.

- 35mm has never been about high quality pictures - in practice - ditto digital, I;d accept that some hobby people tried...

- Ive always found the manufacturers data sheets to be more reliable than web fact, but I think you may be correct, 200 is a better optimum for scanning - but rare that I scan

 

http://www.ilfordphoto.com/Webfiles/...1945161573.pdf

 

Oscar Barnack's cine film in '13 was not that fine grained, but he could take his little camera hill walking.

 

But you can change speed in the mddle of a roll and not do anything else, except post processing to salvage a print.

 

The shots at 10,000 (on XP1) were horrible...

 

Noel

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Hi everybody,

I have recently got into film so I apologize if my question sounds silly.

I have learned that you can push ISO speeds on films and still get good results.

A lot of times people push an ISO 400 film to 1600.

I am wondering what happens if you change the ISO speed of a film in the middle of a roll?

Let's say your shooting a 400 speed film and halfway through you go to a darker environment. Will there be any bad effect to bumping the ISO to 1600 mid-way through the roll?

 

Thanks,

KYle

 

I regularly change asa mid-roll and then develop in either a two bath or Rodinal stand development. Usually with Tri-X, Double-X or ORWO N 74.

 

It's not to everybody's taste but I suggest you give it a try and see if you like it. You are allowed to have fun with photography and experiment.

Edited by MPerson

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