20D vs. 5D for long lens photography

Calculation of the 5D pixel density based on the pixel size of the 20D/30D is completly wrong because the pixel size of the 5D is bigger than the 20D/30D ones. There is no 21MP density equivalence.

 

But then again, when you crop a 5D image down to 3504x2336 pixels (20D/30D pixels resolution) than you have the same resolution as a picture taken with a 20D/30D. But your 5D image will be bigger than the 20D or 30D.

 

So at the same resolution (cropping the 5D image in pixel count) you have a bigger photo with the 5D (roughly 6%)

Now that is an interesting point: a 5D image cropped down to 20D dimensions will be a bigger file. That would seem to make the resulting image better, generally. Particularly because of the lower pixel density, yes?

 

I am going to pore through these answers to arrive at a conclusion, but despite some contradictory responses I thank everyone for taking the time to contribute. This is much more of a response than I even hoped for.

 

Still would like to hear a reply with someone's personal experience of having shot the same subject with the same lens on both cameras, then cropping the 5D image to 20D equivalent size and comparing results. Bob's article speaks to this but there again I will have to read carefully and parse those results. Ultimately I'll just have to try it myself but that is one 5D body away!

<p><i>Calculation of the 5D pixel density based on the pixel size of the 20D/30D is completly wrong because the pixel size of the 5D is bigger than the 20D/30D ones. There is no 21MP density equivalence.</i></p>Would you please expound on this? I'm not certain I understand what you're saying.

The combination of a 20/30D with a long lens and the 5D with a shorter lens is pretty much an ideal combination. I use my 20D with 300/f4+1.4x for sport and wildlife and the 5D with 17-40 or 24-105 for much of the rest.

 

The 20D gives excellent results with longer lenses, I wouldn't hestitate to recomend it.

If the numbers that Matthias gave in his post are correct and they look pretty close to right, then we can make the following statements.

 

If you look at the central portion of the 5D sensor that is the same physical size at the 20D sensor then you get the following

 

Central portion of the 5D sensor:

(22.5*15.0) * 14025 pixels per mm^2 = approx. 4.7MP

 

This makes sense because the 5D sensor has 2.5X the area of the 20D but only 1.5X as many pixels. This seems to indicate that if you were to crop a 5D image to have the same apparent FOV that a 20D has then the 20D would have 3.5MP more then the 5D image and thus would give better results during enlargement. If you crop a 5D image to the same resolution as a 20D then it represents a larger portion of the sensor and will not have the same (apparent) magnification that the 20D give. So it seems that unless you can get a slightly longer optically equivalent lens then the 20D will yield more pixels then the 5D when comparing FOV.

Patrick, I have a 20D and a 5D. I do a lot of bird shooting (though I don't have the pictures up on this site any more) with a 400mm f5.6. Here's the bottom line: If you find yourself needing to crop an image using the 20D and the longest lens you have then the 20D is the better camera to use. Assuming you're not dealing with very low light conditions then pixel density is what counts here. This is why the 20D and the 5D compliment each other so well and why the people at Canon continue to rake in all of our money.

 

Best of luck!