Full Size vs. APC-S sensor comparison

Started Jan 28, 2008 | Discussions thread
T3 Forum Pro • Posts: 20,320
Re: Full Size vs. APC-S sensor comparison

Transitioning from a 35mm analog camera to a 35mm digital camera is obviously going to be more natural than going from 35mm to APS. For example, if you're used to the perspective and depth of field characteristics of a 50mm lens on a 35mm film body, you'll get the same on 35mm digital body. But sticking a 50mm lens onto an APS body becomes quite different. Your perspective is heavily cropped. Look at the diagram below and you'll get an idea of just how heavily cropped things are going to look:

But you can use a 35mm lens instead of a 50mm lens on the APS camera, because 1.6 x 35mm = 56mm, which will give you a field of view that is similar to a 50mm lens on a 35mm body. However, the downside to that is that you're going to get the depth of field of a 35mm lens, not a 50mm lens. In other words, you're not going to get the background blur that you would expect from a 50mm lens on a 35mm body, even though the angle of view is similar to a 50mm lens on a 35mm body. You're going to get less background blur because shorter focal lengths have deeper depth of field than longer focal lengths. That takes a little getting used to. And some people just plain miss not being able to get the shallow depth of field/ nice background blur that they used to get on 35mm bodies.

The other advantage of 35mm sensors is that you get less image noise. 35mm sensors are so much larger than APS sensors that you can have bigger pixels on that larger sensor. And since bigger pixels are able to capture more light, they are able to produce images with less image noise. Smaller sensors generally have smaller pixels, which capture less light, which require more signal amplification at each pixel site, which results in more noise. So a 12mp 35mm sensor will produce less noise than a 12mp APS sensor. And even though the 40D only as 10mp, it still has pixels that are smaller than the 5D's, which means it inevitably produces a noisier image. At lower ISO speeds, there may be no difference, but the difference is more pronounced at higher ISO speeds. Oh, and not only does the 5D produce less noise, it delivers more resolution to boot. But you also have to consider that, whether you're using a 40D or a 5D, the quality that you are going to be able to get at higher ISO speeds is still going to be way better than what you can get from high ISO films. So most likely, you'll be very happy with the high ISO quality that you'll get from a 40D, and simply astounded by the high ISO quality that you'll get from a 5D.

Oh, and not only is the 5D going to deliver lower noise, it has 12mp to the 40D's 10mp. If you're going to be bringing big, those additional megapixels can come in handy.

Also, if you're used to the big viewfinder view you get from a 35mm film body, looking through an APS viewfinder might, at first, feel like looking through a tunnel. The viewfinders of APS cameras, even with high viewfinder magnification, are still smaller than what many 35mm film viewfinders deliver. That's because an APS sensor is so much smaller than a 35mm sensor.

Plenty of people are perfectly happy with APS bodies. And plenty of people love FF bodies. I personally like using both, and so your idea of "getting in with the 40D and later buying a full-frame camera and make the 40D my 2nd body/telephoto camera" sounds perfectly reasonable. It's always nice to have two bodies, anyways.

Bodhidharma wrote:

I'm new here but have been reading quite a bit and you folks seem to
not only be knowledgable and compassionate, but many of your are
really great photographers. So, here goes my first question:

I used to shoot Nikon 35mm for many years, (advanced amatuer/pro).
I'm finally ready to make the leap into DSLR territory and was
looking to get a Canon 40D. Then I saw all the hoopla about no 5D
successor being announced at PMA and been reading a lot about how
many people truly love and respect that camera and it's image making
ability even though it's 2-3 year old technology. The prices here in
US are getting lower and lower on that model and while it once was
out of my price range, now it is not.

I will probably not do a lot of fast sports or anything too extreme
weather wise so I think the 5D could work for me. I'm curious as to
just how much better the image quality would be between a 40D and 5D
if shot side by side? I like to shoot portraits, still-lifes,
travel, landscape, and night photographs mostly. As I'm just getting
back into photography I don't have myself set up to do my own
printing yet, but I'm interested in making up to A2 size (17"x22")
prints and wonder if I'll notice that much difference in quality up
to that size?

Both cameras have pros and cons and both will suit me fine. I just
wonder if this might be a good time to just jump in at the
full-sensor level and cut to the chase? Or would I be better served
getting in with the 40D and later buying a full-frame camera and make
the 40D my 2nd body/telephoto camera?

Again thanks for your time and any help would be greatly appreciated
as I'm just waiting for my least favorite relative, "Uncle Sam" to
give me back a bunch of money he's taken from me last year, so I can
start shooting again.

Happy Shooting!

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