Stupid question

LWSC

LWSC

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Lucas
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Hello all. This is probably a thick question but I just want to make sure I'm not making an error: the light meter on my camera is about 2 stops out (if I exposed according to it everything would be overexposed) so if I "trick" it by setting the ISO value to two stops below (100 if I'm using 400-rated film) then I can still use it to expose by accurately. Presumably this will make no difference to the actual film/exposure on the film, as changing the ISO value on the dial doesn't do anything to the film itself - right? So I can merrily set my ISO dial to 100 when exposing HP5 (to trick the light meter) and thereby expose for what I know is 400 speed film. Correct?
 
Correct.

(To be pedantic, you might want to check that the error is linear - is it two stops out at all light levels? - but in general, it'll work fine)

Edit: don't answer posts at 2:42 :D
 
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NO, that's the wrong adjustment to make. If it meters such that the result would be overexposed, then it lets in too much light; setting the ISO to 100 instead of 400 would let in even more light. You should set it to 1600 instead.
 
Well you can always check it with your digi or spare film camera or some can use a mobile phone or at a last resort "sunny 16".
 
I'm with Nick. Use 1600.

Or as Brian says, ignore the meter.
 
NickT said:
NO, that's the wrong adjustment to make. If it meters such that the result would be overexposed, then it lets in too much light; setting the ISO to 100 instead of 400 would let in even more light. You should set it to 1600 instead.
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I'm a little confused: when you say it will 'let in more light', which 'it' are we referring to? Presumably as there's no change in the aperture and no change in shutter speed - and changing the ISO dial on its own can hardly change the sensitivity of the film - we just mean the meter rather than the actual exposure?
Also, I don't see why I would want to meter on 1600, as then my shots would be overexposed by two more stops, wouldn't they? As it is now, when I set the ISO dial on my camera to 100 it matches the meter reading (say 2.8 at 1/125) on my handheld meter when the latter is set to 400.
 
Have you checked the camera's light meter against another light meter that you know is accurate, as it might possibly be a case of the light meter being 'about right' (or just 1 stop out) but the camera's shutter speed is running slow? This won't be a perfect comparison but a 2 stop difference should be fairly obvious. If you try this idea then choose a day with flat, constant daylight, because 'patchy cloud with sunny intervals' will drive you mad when trying to get a constant light level for long enough to do the test! Hope this helps and the rest of the forum think this idea has some merit. :)
 
Have you run a film through the camera using the metered settings and correct film speed? How did it turn out?

It's also worth checking the batteries are the right ones as incorrect batteries or tired batteries can have all sorts of effects on metering. Some cameras are more affected than others.

Which make/model of camera is it?
 
LWSC said:
I'm a little confused: when you say it will 'let in more light', which 'it' are we referring to? Presumably as there's no change in the aperture and no change in shutter speed - and changing the ISO dial on its own can hardly change the sensitivity of the film - we just mean the meter rather than the actual exposure?
Also, I don't see why I would want to meter on 1600, as then my shots would be overexposed by two more stops, wouldn't they? As it is now, when I set the ISO dial on my camera to 100 it matches the meter reading (say 2.8 at 1/125) on my handheld meter when the latter is set to 400.
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If you set your meter to 400 and the results you get are overexposed when you use the shutter speed/aperture suggested, then if you were to set the meter to 1600, it would suggest a faster shutter speed or smaller aperture.

If you were to set the ISO to 100, then the meter would suggest a slower shutter speed or wider aperture. That would make the result even more overexposed.

Telling the camera that you have a slower film inside would result in more light getting to the film, making it more overexposed.

I would have thought the answer was obvious, I can't put it any more clearly.
 
LWSC said:
Also, I don't see why I would want to meter on 1600, as then my shots would be overexposed by two more stops, wouldn't they? As it is now, when I set the ISO dial on my camera to 100 it matches the meter reading (say 2.8 at 1/125) on my handheld meter when the latter is set to 400.
Click to expand...

If you want to reduce the amount of light reaching the film by two stops, then you'd expose a 400 ISO film at a 1600 ISO meter setting. Exposing a 400 ISO film at settings for a 100 ISO meter reading will allow 2 stops more light to reach the film, thus overexposing it. Hope this makes sense?
 
Principle sounds reasonable, BUT, I'm going to take a step back, and ask WHAT CAMERA?
And, sounds like you are trying to 'calibrate' the meter with the camera 'dry' with no film in.
Olympus OM's are particularly perverse for this; they have a curiouse 'Off The Film' metering system, that takes a reflected light reading, in camera off the fim... IF there's no film in the camera, or the back's open... it dont see a representative reflection, and metering can be all over the place.
OM10's also have a peculiar little bit of plastic covering some of teh circuitry in the mirror housing that often falls off, and can drop infront of the sensor, whilst they all have a patterned shutter curtain with a curiouse matrix of white squares on it that's supposed to mimick the reflectivity of the film, when metering off the shutter before exposure, that can if dirty effect meter calibration.
Other film cameras, I am sure have similarly idiocyncratic systems, before getting to questions of the balenced circuits and compatible battery voltages....
BUT.. unless we know how you are trying to calibrate.. we could be giving you duff advice, that's redundant, and when you go put film in and take a picture, your 'compensation' results in over exposure, as the meter might not have been 'wrong' or so wrong to start with.
 
Right, I see - what I should have said is that the shutter speed/aperture combination the meter tells me I should use would combine with the actual sensitivity of the film to underexpose the film, but if I set the dial to 2 stops less sensitive than the native ISO of the film, it gives me a correct meter reading as compared with a handheld meter I know is accurate. The camera is a Leica CL, so the meter is a cds cell on a little stick thing between lens and film (no reflected readings, like on later Leica models)
 
LWSC said:
Right, I see - what I should have said is that the shutter speed/aperture combination the meter tells me I should use would combine with the actual sensitivity of the film to underexpose the film, but if I set the dial to 2 stops less sensitive than the native ISO of the film, it gives me a correct meter reading as compared with a handheld meter I know is accurate. The camera is a Leica CL, so the meter is a cds cell on a little stick thing between lens and film (no reflected readings, like on later Leica models)
Click to expand...
Tbh I'd use a handheld meter!
 
LWSC said:
Hello all. This is probably a thick question but I just want to make sure I'm not making an error: the light meter on my camera is about 2 stops out (if I exposed according to it everything would be overexposed) so if I "trick" it by setting the ISO value to two stops below (100 if I'm using 400-rated film) then I can still use it to expose by accurately. Presumably this will make no difference to the actual film/exposure on the film, as changing the ISO value on the dial doesn't do anything to the film itself - right? So I can merrily set my ISO dial to 100 when exposing HP5 (to trick the light meter) and thereby expose for what I know is 400 speed film. Correct?
Click to expand...
LWSC said:
Right, I see - what I should have said is that the shutter speed/aperture combination the meter tells me I should use would combine with the actual sensitivity of the film to underexpose the film, but if I set the dial to 2 stops less sensitive than the native ISO of the film, it gives me a correct meter reading as compared with a handheld meter I know is accurate. The camera is a Leica CL, so the meter is a cds cell on a little stick thing between lens and film (no reflected readings, like on later Leica models)
Click to expand...

You see where people are a bit confused- is it overexposed or underexposed?
 
To avoid confusion, are the photos from that camera too dark or too light when using the settings from the in-built meter?
 
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kendo1 said:
You see where people are a bit confused- is it overexposed or underexposed?
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Oops, just literally mis-typed the first time round, sorry! Underexposed, of course, not over
 
abdoujaparov said:
Correct.

(To be pedantic, you might want to check that the error is linear - is it two stops out at all light levels? - but in general, it'll work fine)

Edit: don't answer posts at 2:42 :D
Click to expand...

LWSC said:
Oops, just literally mis-typed the first time round, sorry! Underexposed, of course, not over
Click to expand...

I shouldn't author threads at 2.38 either! :)
 
LWSC said:
Oops, just literally mis-typed the first time round, sorry! Underexposed, of course, not over
Click to expand...

:D wally

In which case set to 100 ISO, as you have found out.
 
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