Experimenting with Exposure Indexing, 24 September 2009


I have already written at length about Exposure Indexing and it’s various effects on the resulting images, so I won’t retread over ground already covered. I’m also tired and trying to figure out how to build a roof cricket, so I suppose it’s fair to say that I’m not entirely focused on matters photographic, at this point. As such, have fun with the photo.


Photo Information:

Camera: Canon AE-1 Program
Lens: Canon 24mm f/2.8 FD
Film: Ilford HP5+ ISO 400 (shot at EI 1600)
Exposure: TTL metering

The subject of the photo, obviously, is the southwest view of the Chicago River from the Michigan Avenue Bridge – those of you who have read some of my previous photography posts have probably seen this view a few times. As I’ve mentioned before, it is one of my favorites, so this may not be the last time the composition makes an appearance here.

I’ll briefly note two things about the photo. First, notice that even with the increased visibility of the film grain, the film still captured a fair amount of detail from the various buildings, and even from the water in the river. Second, notice that the lens I used to capture this photo is a wideangle focal length for a 135 (35mm) camera; even though lenses of this type will always exhibit some degree of distortion, there is actually very little distortion to be seen in this particular case. One of the reasons for this relative lack of distortion is that the lens itself is a “prime” lens – i.e. it has a single, fixed focal length, as opposed to a zoom lens, which has an adjustable range of focal lengths available to it. [1] One important aspect of such prime lenses is that their optical elements can be very specifically designed to handle only one focal length; in zoom lenses, on the other hand, the optical elements must be designed to operate at a range of different focal lengths and, as a result, cannot be optimized for a specific focal length. The end result, as seen here, is that the lens can, under the right circumstances, produce superior results to what one can achieve with a similar setting on a zoom lens. [2][3]



[1]: Note that the term “Prime” may also refer to the primary lens for a system camera (typically a normal lens, but this depends on the manufacturer and camera model).

[2]: I have noticed a rather jarring contrast between photos I’ve shot on my film cameras using prime lenses, and those shot on my digital camera at a similar focal length setting. Specifically, the zoom lens on my digital camera tends to exhibit far more distortion than the prime lenses on my various film cameras.

[3]: As a rule, I prefer using prime lenses, even if it means that I need to carry multiple lenses. Granted, most medium format SLR systems do not have zoom lenses anyways, but modern AF SLRs and DSLRs are often combined with various zoom lenses, and while camera manufacturers still produce prime lenses, the variety of available primes is far less than it once was. I find this somewhat sad. My favorite lenses are prime lenses, so much so that I often leave my zoom lenses at home when I’m out with one of my system cameras.


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