The Canon EOS and Photography Forums

The new (revised) article is great, but I think you need to put some discussion of sensor sensitivity (ISO) in there.

Digital photography now has *three* exposure dimensions:
Shutter speed - trade off of camera and subject motion blur
Aperture - trade off of depth of field
Sensor Sensitivity - trade off of noise.

All three can be set for any image.

For film, the film would generally fix the sensitivity *and* color balance.  While it is *possible* to change films, in practice, I think it was rarely done.  Even with my APS SLR which actually had that functionality, I think I may have done it twice per thousand rolls of film.  (Of course, I did not have that many film choices, anyway!)

(I have in my head a presentation about this called "Digital Photography - to the fourth dimension!" which adds white balance to the list.)

Keith - That's an excellent point. As you say, when I originally wrote the article, changing ISO wasn't much of an option. Though you could switch films, it was a pain. One of the great advances of digital is the ability to switch from ISO 100 to ISO 1600 and back again on sucesssive frames!

UPDATE:

I added a section on ISO settings and while I was at it I also added a section of the use of neutral density filters to contriol exposure. They are at the end of Part I of the article
(http://www.bobatkins.com/photography/technical/all_about_exposure.html)

Interestingly, this is the same subject of Bryan Peterson on photo.net which is I think taken from his book Understanding Exposures.

These are really very good for beginners or those who forgot the basic.

Thanks Bob.

I hope the article is useful. I did see Bryan's article for photo.net since I'm the technical editor there, so these things come across my desk, but that didn't trigger my article here (which is a bit more technical I think). I actually have a bunch of technical articles which I wrote for publication about 10 years ago and I'm slowly updating them (and converting them into HTML documents for the web) to reflect changes in photography since they were originally written (mainly the rapid advances in digital imaging). There's one on polarizers and a failry long one on depth of field issues that I'll be adding to the pages here before too long.

I will be looking forward for these articles Bob.

Thanks for always sharing.