Quote Originally Posted by neuroanatomist


I concur with what Ben said, for the most part. The only point I'm not sure about is "There's a pretty big step up in image quality between the 40/50D and the 7D." There's a big step in resolution between the 40D (10 megapixels) and the 7D (18 megapixels), but not much a step from the 50D (15 megapixels) to the 7D. The 5D, as a FF camera, is a significant step up in terms of image quality especially in the ISO noise performance. But keep in mind that with FF, you lose the 1.6x crop factor - in practice that means that if you find yourself frequently cropping your images, you'll lose the benefit of FF (look over your current shots - if you crop shots from your XSi already, a 5D will be worse than the XSi, for you).


Taking FF out of the picture, ISO noise may be a differentiator - from Bryan's review of the 7D, "I'm particularly impressed at the Canon EOS 7D's noise performance against the 50D. Comparing the gray blocks at the top of the 50D's image shows the 7D to have a slight advantage over the 50D at ISO 800 that builds to a solid advantage at ISO 3200. By ISO 12800, the 7D solidly outperforms the 50D." However, as a 7D user I'm not particularly thrilled with ISO 3200, which still looks pretty noisy to me even after cleanup of the RAW file. But then again, an image that's shot at ISO 3200 on the 7D, not cropped much, and printed 8x10" still looks good. The 7D may 'solidly outperform' the 50D at ISO 12800, but I've never been desparate enough to go that high.


In terms of ISO noise on the 40D vs. 50D, they are pretty similar there (and kudos to Canon for a 50% increase in pixel density without taking a hit on noise!).


Having said all of that, honestly, there are not going to be huge differences in image quality between the XSi that you have and the 50D or 7D. Incremental differences, yes. But not huge. I upgraded from a T1i (very similar IQ to the 50D) to a 7D, and really didn't notice a big difference based on sensor performance. IMO, the biggest differences are in other areas.


Build quality takes a big step up from XSi to 40/50D, and another noticeable step up from 50D to 7D. The ergonomics are also better, IMO - having the dial and joystick on the rear means much faster adjustments of image parameters than on a Rebel.


As Ben mentioned, AF Microadjustment can be a significant benefit. Most of my lenses have some amount of adjustment applied. Beyond the microadjustment feature , the AF performance itself will be a bit better with the 50D (9 cross-type sensors) vs. your XSi (similar 9 points, but only the center is cross-type). The 7D's AF system is excellent, with 19 cross-type sensors and lots of customizable options for AI Servo tracking.


If you do shoot wildlife/birds/sports with your 300mm f/4L that's on your camera 90% of the time, the other big benefit you'll notice is frame rate. Your XSi is 3.5 fps, the 40/50D are nearly twice as fast (6.5/6.3 fps), and the 7D is over twice as fast with 8 fps. Here's an example of two successive frames from an 8 fps burst:


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.35.15/IMG_5F00_2847.jpg[/img] [img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.35.15/IMG_5F00_2848.jpg[/img]


EOS 7D,EF 100-400mm f/4.5-5.6<span style="color:red;"]LIS USM @ 400mm, 1/2000, f/6.3, ISO 3200


On the whole, if your reasons for wanting to upgrade your camera body are primarily around image quality, I'd say keep the XSi and consider lenses (what's that other 10% shot with, and do you want better IQ there?), a Speedlite flash if you don't have one, etc. In general, lenses have a much greater impact on image quality than the camera body.


But, if your reasons also include overall performance, ergonomics, etc., then an upgrade is worthwhile. In that case, you can't really go wrong with the 40D, 50D, or 7D. If you can stretch your budget to cover the 7D, it's an amazing camera. If the 50D fits your budget, I'd get that over the 40D.



Good insight, as usual. I do have one question for you though. You say in one sentence that most of your lenses have at least some AF Microadjustment applied to them, so that seems to imply that your IQ would be improved even with just a 50D over a 40D, all else being equal, regardless of resolution advantage.


Then later you said that if IQ were the only concern, that you'd keep the XSi and get better glass. If I am not mistaken the XSi doesn't have AF Microadjust, and wouldn't it be better to optimize the good glass he already has more than buy more glass? I think the 300/4 is an already excellent lens, and it seems like a clear way to optimize it is by properly adjusting its AF to match the body perfectly.


These are really questions to which I don't know the answer, so please don't take it as argumentative. Since I haven't experienced AF Microadjust, and I don't honestly know if my 40D is off with either or both of my current lenses, I don't know what I'm missing. Based on some shots I see here, when compared with some of my own carefully AFed shots, I wonder if mine is slightly out, though, and the problem is I don't think there is anything I can do about it without changing bodies.


Am I wrong?