Cropping with 40D vs. 7D

[ammagal]

Bob,

Your nice review of the 7D points out that, under normal conditions (eg., not much information in the highest spatial frequencies in the image), the 40D doesn't lag behind that much in resolution when an image is cropped and appropriately compared (i.e, taking into account the pixel sizes of each camera as you did).

I have a 40D and enjoy bird photography with my 100-400mm f/5.6 Canon zoom. Would that comparison mean that there wouldn't be much to be gained by cropping images taken w/ the 7D compared with 40D crops? You end up doing frequent crops in bird photography, and this the reason I'm asking.

I'm neglecting here the several new features of the 7D, of course, such as its new AF system. Could you please care to comment on the AF speed vs. the 40D's, again with bird photography in mind?

Thanks,

Antonio

[Bob Atkins]

If you have a good enough lens (e.g. one of the Canon telephoto primes), then there would be something to be gained by using a EOS 7D over a 40D, especially if you are making large prints or medium prints after significant cropping. The 7D will record more detail, if that detail is present in the subject and if the lens is capable of resolving that detail with good contrast. If you are using a consumer grade telephoto zoom, you might not see much difference. The 100-400 IS is a pretty decent lens, so I suspect that you would see a little more detail in the 7D images.

As for the AF system of the 7D, it's better. It may track a little better in servo mode, so that sharper "birds in flight" images may be easier to get. It has a higher density of AF zones which will help to hold focus if the subject moves around in the viewfinder. On a static subject both systems should be equally accurate. The AF system of the 7D is certainly much more versatile and clearly an improvement on that of the 40D.

The best AF performance of any EOS body is found on the EOS 1D MkIV (which I'm currently testing). However at $5000, it's out of the reach of most amateurs (including me!).

[ammagal]

Great, thanks for your input, Bob.

About the 1DMIV, yeah, no kidding... :-) I too can't justify that expense either, at least until I retire from the University and start selling more photos! ;-)

On the other hand, I've switched (haven't we all, I guess) to greater emphasis on glass. Eg, 5 grand on a 500mm f/4 would be instead something not too insane perhaps, especially knowing that lenses do not devaluate that much over time (this line is what I'm hoping to convice my wife with...).

The $6k question of course is whether my good ol' 40D could make good use of it, esp. in the AF arena, knowing I could move to a 7D when an '8D' comes out in a couple of yrs.

Cheers,

Antonio

[Bob Atkins]

You're right that good lenses don't lose a lot of value over time, and if you can buy them used you lose even less. The only exception is perhaps when a newer, better version of a lens is released, but with the long telephotos that's probably not going to happen. It's possible at some point they might update the IS on them. They were all released quite a while ago and so have fairly early IS systems with a 2 stop capability. Most currently released IS lenses have 4 stops, but I don't know if the updated technology would be applicable to the long telephoto lenses.

Of course new versions always come with a sizable price increase, so the devaluation of the previous model isn't so bad. On the other hand new camera upgrades are often cheaper than the models they replace, so the devaluation of older models just gets worse! You can lose 80% of a camera's value in a few years, but with a good lens you're very unlikely to lose more than about 20%, even if you buy it new.

[marcfs]

I have a 7D and 40D.   The 7D replaced a 20D that was my backup camera.  The 40D is now my backup camera.  Birds are a primary area of focus, and when I shoot birds I am primarily using a 500 and 1.4 extender.  I also use the 400 f/5.6 L for BIF.

So far I have found the 7D to provide the following advantages (and I am constantly learning new ones) over the 40D:
•   Significantly better AF system in AI Servo
•   Overall better focusing with AF expansion
•   Spot AF
•   8 frames per second image capture
•   Ability to capture images at high ISO’s
•   Ability to use auto ISO
•   Greater ability to crop versus 40D
•   Print output is excellent
•   Many others, such as battery, etc.  You can read Bob’s review for more details

Negatives: 
•   Need to put in the required time to learn how to use camera and set it up correctly
•   Using the 40D in AI Servo on center point is very straight forward and effective;  7D requires more initial work (big payoff)


I still like the 40D and it is a good camera with solid IQ.  IMHO the 7D is one step closer to a one series, but this is probably true about each new Canon entry.

You can view my 7D and 40D images on my website.  The majority of images on the home page slide show were captured with a 7D.  In the featured gallery, NY-NJ Wonders, camera and lens details are listed for each image.  BTW, one of the images in the slide show was captured with a Panasonic LX-1. 

Good luck with your decision.

Marc
www.marcschoenholz.com