# ISO adjustments on film camera?



## crumpy

Hello people,

First post! 

So, anyway, I am new to all this and I have a question. I know what different ISO ratings are and mean and what effect having High or low ISO films would have. 

However, what has me baffled is that my film camera has a little knob that I can turn to adjust ISO. what exactly is this adjusting? my films ISO is set, I have manually adjustable shutter speed and aperture. so what changes when I turn that little knob?

my dad says it's just to remind you what film your using but I can't believe that... 

thanks in advance from a properly confused Crumpy


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## Sam6644

you can't change the ISO of film. The film is rated at a specific ISO and you turn the knob to that ISO to make sure you're light meter is aware of your film's light sensitivity so it can give you an accurate reading. 

You can turn the knob to push film, and meter as though you're using a higher ISO but that requires extra attention in the dark room afterwards. 

Unless you understand pushing ISO, you're dad is pretty much right- its just there to remind you whats in there.


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## rallysman

This is a complete stab in the dark, but maybe it lets the camera know what film it has for auto modes.

I really don't know for sure, but that seems to be the most logical at this point (until someone that is certain speaks up)


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## Josh66

It's so you can cheat.

The (modern) camera reads the ISO from the film canister and sets it accordingly.  You can change it though.

Say you want to do a multiple exposure.  Set the ISO to half of what it really is and your 2 shot multiple exposure will be properly exposed.


Changing the ISO on a film camera is pretty much the same thing as changing exposure compensation on a digital camera.

Also - some films perform better at an ISO other than the spec on the box.  This lets you tweak it.


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## ann

setting the ISO guides the meter to suggest options.

it is very common for serious film uses to change the box speed to something else they have tested for and develop accordling.

modern film is coded and if you use a cansister that isn't the meter usually defaults to an iso of 100, which indicates to the meter that this is a slower film and then the meter gives recommendations for what fstop /shutter speed will be needed for 100 speed film regardless of what the film might be.

on many cameras you can over ride the coding by setting the ISO dial yourself.


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## crumpy

thanks for the quick response!

It's a really old camera so there's no auto modes.

but there is a really basic light meter when you look into the view finder.

so, its just to tell my camera what film I have in there so that the meter is accurate. that makes sense. should have thought of that.

so any camera without a light meter will not have an ISO dial?


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## Josh66

crumpy said:


> so any camera without a light meter will not have an ISO dial?



Without a meter, there would be no reason for the camera to need to know what ISO film was in it.


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## crumpy

sweet. thanks for clearing that up for me. was really annoying me! lol


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## matfoster

rallysman said:


> This is a complete stab in the dark, but maybe it lets the camera know what film it has for auto modes.



for automatic cameras, this is achieved by DX encoding.
DX encoding - Wikipedia, the free encyclopedia


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## compur

crumpy said:


> so any camera without a light meter will not have an ISO dial?



Lots of older cameras without meters have an ISO dial. (Actually it was 
called an ASA dial in those days.)  But, the dial on a meterless camera
was used as a reminder or, sometimes, it linked with an optional meter
attachment that could be mounted on the camera.


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## djacobox372

There's an iso dial on the bottom of my meter-less nikon F, but all it does is serve as a reminder as to what film I've loaded in the camera.


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## matfoster

torn-off endflap of the film's box, slipped into the memo holder looks cool .


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## Battou

crumpy said:


> so any camera without a light meter will not have an ISO dial?



Not true, I have a handfull meterless cameras and all but three of them have an ISO dial, two lacking one are simple box cameras so technically they don't count  the other is one of my range finders but yes as a couple have mentioned it is there mostly to remind the user what is loaded into the camera. the camera shown here is one such camera, it has no meter but at the right on the advance knob is an ASA/DIN indicator (the red you can see in there).


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## Josh66

Some films just seem to look better with a stop or so overexposure, so being able to change the ISO is useful for that.

Portra 160, for example - I usually set the ISO to 80 or 100 for that.

You _could_ do the same thing without changing the ISO, but it's just easier that way.  You don't have to remember to overexpose it a stop every time - you just set it once and forget it.  Very similar to dialing in +1 EV compensation on a digital camera.


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