The Crop Factor

[davidb]

Here is an interesting article explaining the difference between the sensor in a full frame camera and a camera with an APS-C sensor.

http://www.eos-magazine.com/articles/eo ... actor.html

It's more for the like of myself and other beginners; Mike Farley and his ilk will find nothing new in the article.

[Mike Farley]

Mike Farley and his ilk

We're inseparable. I never leave the house without it.

The article is OK so far as it goes. It very sensibly does not mention depth of field or equivalent apertures, which can get some correspondents on Internet fora so excited. In many instances, such considerations have no material effect on the final image. Instead it recommends simply getting on with your photography and leaving such matters where they mainly belong. With the imaging scientists.

Which is what I should do, except there are a couple of things which are nagging me. The first concerns the statement "the full-frame sensor is 1.6 times bigger than the APS-C sized sensor". That is certainly true when it comes to the length of the diagonals on the respective sensors, where there is a 1.6* ratio. It is that dimension which determines the crop factor. When it comes to the overall area which is one of the factors which determines high ISO performance, a full frame sensor is actually 2.6 times larger than Canon's APS-C one. Within the frame of reference for the article, it is not necessarily relevant but is misleading.

For anyone interested in the details, this article has all the facts and figures - http://photoseek.com/2013/compare-digit ... inch-type/.

More disingenuous is the suggestion that the user has a choice when it comes to using EF lenses on one of Canon's APS-C cameras. The implication of the article is that there is a full range of lenses in all three of the mounts (EF, EF-S and EF-M) which Canon offers. That just is not the case. There are relatively few EF-S lenses available and even less for EF-M. What is on offer are mostly zooms with slow apertures. Anyone wanting a fast prime lens or a telephoto will usually have no option other than to choose an EF model. This does not hold just for Canon, both Nikon and Sony have similarly failed to support their APS-C customers.

* The APS-C sensors from other manufacturers are slightly larger, which means that the crop ratio is fractionally smaller at 1.5.