Start accepting the pro-photographers are not perfect.

[JohnBoy]

Long time since I've been here - must visit more often. I agree that it is reasonable for the instructor to insist on a fixed ISO when teaching studio photography but I just wonder why 100 and not 200. I've yet to use a digital camera that produces better image quality at 100 than at 200; after all their sensors do not behave like film and 200 seems to be the "natural speed" of most sensors. With modern studio lights offering a minimum power setting of at least 1/32nd, I can't see that anyone would often need 100 ISO even to achive minimum DOF with very fast lenses wide open. As you would guess, I don't use ISO 100 and I do a lot of studio work under flash.

 

[Vtec44]

I'm perfect!

 

[photog15]

Trying to teach people with only one ISO is not teaching. This is extremely limiting and it's hard to believe someone thinks that's a good way to open people's minds to the many different ISO types and the results they produce. Maybe for an assignment or two that's fine but all the time? She wouldn't get my money!

 

[Designer]

I think there is a valid reason for it, which I've already posted.

 

[Bebulamar]

I think of lighting as the 4th leg of the exposure "triangle". People forget that in addition to changing the shutter speed, aperture, or ISO... you can ALSO change the lighting.

I agree that lighting is a mean of controlling exposure. If we really think about it ISO is not part of exposure.
1. If you add more light the subject is brighter and thus more exposure.
2. If you use a larger aperture, more light gets thru and thus more exposure.
3. If you open the shutter longer that's more exposure.

If you you increase the ISO the resulting image is brighter with the SAME amount of exposure and thus the exposure doesn't change with a change of ISO.

 

[Forkie]

I've never formally studied photography except for a one week studio lighting course a couple of years ago and we all shot at ISO 100 the whole time.

I agree with the people here who say that in a studio, there is no need to shoot at anything higher than ISO 100, especially if you are shooting commercial, advertising grade images - you don't want any hint of noise in your images whatsoever, unless perhaps you are doing conceptual editorial shoots where noise is needed for artistic purposes. I rarely shoot over ISO 64 in the studio - there's no need.

 

[Overread]

I think of lighting as the 4th leg of the exposure "triangle". People forget that in addition to changing the shutter speed, aperture, or ISO... you can ALSO change the lighting.

I agree that lighting is a mean of controlling exposure. If we really think about it ISO is not part of exposure.
1. If you add more light the subject is brighter and thus more exposure.
2. If you use a larger aperture, more light gets thru and thus more exposure.
3. If you open the shutter longer that's more exposure.

If you you increase the ISO the resulting image is brighter with the SAME amount of exposure and thus the exposure doesn't change with a change of ISO.

If ISO was just a "brighter" photo then yes this would be true - but its not.

You can try this yourself by setting an aperture and shutter speed which at ISO 100 would result in a fully black, ergo underexposed, photo. Sure you might be able to get some information back, but chances are you won't you'll get black, some info and a LOT of noise.

Now raise the ISO up to a decent level to get a good exposure and compare the results. Your second shot with a higher ISO will have less noise and more general detail and contrast and richness in colours.

So for a photo ISO is part of the photographic exposure. Just like the ASA was in the film days - the only difference is that today we've got the ability to change the ASA/ISO on the fly (ok you could do this with some film cameras, but it was slower and required carrying multiple film backs). Also new sensors (esp the Sony ones) are significantly improving the recovery possibilities with underexposed photos. Though whilst there is improvement it still won't equal a higher ISO and a proper exposure.

 

[Bebulamar]

I didn't mean that changing the ISO doesn't have an effect on the resulting image as it does. It is difficult to explain but ISO or sensitivity isn't the exposure. You give the film (or imaging sensor) an exposure which depending on the film (or sensor) sensitivity to light (ISO). If you change the sensitivity the result changes but the exposure is still the same. The exposure is a product of Light Intensity times Duration. To change the exposure the Intensity and/or duration must be changed. Changing the sensitivity you get different results but the exposure is still the same.
In another word if 2 people sun bathing in the same location for the same time they both receive the same amount of exposure to sunlight and UV radiation but one person suffers skin burn and the other does not because their skin have different sensitivity to UV radiation but they both receive the same exposure.

 

[chuasam]

I shoot at ISO 64 so there
Seriously, shooting at your lowest ISO is like driving around in only one gear


Sent from my iPad using Tapatalk

 

[Overread]

Bebulamar - yes the exposure is still the same if we stick to the hard-science definition of exposure. ISO has no effect here since its the light amount times the time exposed.

However in general conversation most photographers include ISO because they are talking about the photographic exposure they have - or rather the results of the exposure on the medium which includes the ISO/ASA value as a variable.