Trading 5D for 50D for crop sensor?

I think what I am looking for is for someone to confirm my logic.
For better or worse, I now have 300 f/2.8 canon lens and photograph birds.
My lens has a 2.5 meter min focal length, and my 5D has a full frame sensor, so I found that
photographing tiny birds was challenging w/o a TC. Without a TC the tiny birds
fill up only maybe a quarter of the frame. And with all shots the ff sensor does not give the
zoom boost the crop sensor does. When I went from the Xti to the 5D I started shooting
everythiing in ISO 400-640 and am worried the 50D will make me wary of these modes like I was
with the Xti. From what I have read, that will no be the case.
Lastly, I think the full frame sensor gave me a lot of indirect image stabalization, and am
wondering if my handheld images will suffer with the 5D and the smaller sensor. I havent
seen much discussion about this.
thanks much,
tom

Tom,
The crop factor has nothing to do with telephoto reach. (I think I've typed these words a dozen times on BPN and other groups in the past week.) Here is stuff I posted in a recent thread:

First, crop factor does not affect telephoto reach. The keys for pixels on subject are:
1) distance to subject, 2) focal length, and 3) pixel pitch.

So moving to a camera with a smaller pixel pitch will help. You might check the recent thread on a birding setup:
http://www.birdphotographers.net/for...ad.php?t=50170

This is from that thread (with some editing for clarity):
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A couple of years ago a cutting edge combination was a 500 mm on a 1D Mark II with 8 frames per second. The key in this is the 8.2 micron pixels. The means that one pixel sees 206265*.0082/500 = 3.4 arc seconds.
The rig weighs about 11 pounds. (smaller arc-seconds means more pixels on subject)

Then came the 1D Mark III (7.2 micron pixels) + 500 mm which = 2.97 arc-seconds and weighs about the same as the combination above. (1DIII = 2.54 lbs + 500mm f/4 = 8.53 lbs = 11.07 lbs)

Now look a 7D (4.3 micron pixels) with a 300 mm f/4 L IS lens: 1 pixel is 2.95 arc-seconds.
7D = 1.8 pounds + 300 mm f/4= 2.6 pounds = 4.4 pounds.

The 300 f/4 +1.4x TC = 420 mm f/5.6 and autofocuses on the 7D and the 300+1.4 is very sharp.
And you have 8 frames per second. less than $3,000 for camera + lens + 1.4x TC.

Much lower cost, much lower weight. What do you lose over the 500 mm + 1D Mark III? Weight and a little bit of high ISO performance, and 2 extra frames per second; but you save thousands of $ and you get more pixels on the subject than either of the above 1D + 500 mm combinations.
----------

Note, a 50D also has small pixels and will have similar effect to the above. The pixels on subject over the 5D (or do you mean 5D II?) will be: 5D: 8.2 micron pixels / 50D: 4.7 microns = 1.74x. The signal to noise ratio will also drop by the same factor, so if you liked ISO 640 on the 5D, then about 400 on the 50D would be the equivalent noise wise. If you mean the 5DII, then the increase in pixels on subject will be 6.4/4.7 = 1.36x.

Regarding image quality, yes it will be tougher with smaller pixels, but the 300 f/2.8 is a wonderful lens so I wouldn't worry about it (or use a tripod and gimbal head). As you push resolution up, it will get harder and
harder to get sharp images. But people do it all the time, just develop good technique.

Back to crop factor. This web page explains the effects and gives the equations for the number of pixels on the subject:
http://www.clarkvision.com/photoinfo/cropfactor

<!-- / message --> Roger

Although the 50D is one of the best cameras in terms of photographing birds in flight, the noise is quite bad. I sold mine, as I believe many have, after only a few months. If yo go back in this forum, you will see several threads regarding the 50D. The 7D may be an alternate possibility.

I have had crop cameras for about 5 years. Had a 50D and just sold it and picked up a 7D. Last year I purchased a used 5D. I don't use it as much and thought about selling it but I shot my sisters wife's wedding and a few other events this summer. Had my 24-105 on the 5D and 70-200 on the 50D. That 5D sensor sure has this quality to it for portraits. If you can swing maybe keep your 5D if you can. I'm glad I held onto mine. I'd never use the 5D for birding though.

If you can afford it, go for the 7D.

http://www.prophotohome.com/news/200...utofocus-king/

Another link

http://www.prophotohome.com/news/200...-torture-test/