I have been shooting with the Canon 7D seriously for about three months now and I thought it would be a good time to offer some thoughts on the performance of this camera body in respect to primarily bird photography. In the last blog on the 7D I gave my initial impressions, but I wanted to take more time and explain the pros and cons of this camera in detail. The Canon 7D (classic) was originally launched in late 2009 and was replaced in 2014 by the Canon 7D Mark II. Packed with a ton of features for sports and wildlife, the Canon 7D was the flagship APS-C camera offered in Canon's DSLR lineup and remained in the place until the release of the Mark II. Among the features on the 7D are an 18 megapixel sensor, 19 cross type AF points and 8 frames per second continuous shooting. Canon's target market for this camera was professionals and advanced amateurs looking for "pro" features and the added reach provided by the APS-C sensor.
When I was searching for a lighter and higher megapixel camera to compliment my aging Canon 1D Mark II, this camera was at the top of my list. The purpose of this blog post is to examine overall quality, noise performance, auto-focus performance and image quality and finally cost/benefit analysis.

Overall Build Quality and Ergonomics
 Let me just say as with any higher end Canon product, this camera is rugged and ready for any outdoor adventure. It is weather sealed against dust and light rain, and is constructed from magnesium alloy. Coming from a 1 series body which are the most durable of all Canon bodies, I can say this camera is comparable, but perhaps not quite as rugged. My feeling is that the 7D will take a drop from backpack level and still be functional although I would not try this.  
 Additionally I like the button layout of this camera as well as the joystick on the back of the camera which is used for moving around the menu options and working in live view. This is the second camera I have owned with live view and I really like using this feature when in a blind photographing birds or shooting still life photographs. Sometimes, it is difficult to be at an angle to look through the viewfinder and the live view functionality makes it easy on my 41 year old neck. In live view I can also easily see my f-stop, shutter speed and histogram information thus allowing me greater flexibility in controlling exposure and previewing my image. The downside to using live view for birds on a perch is it reduces the continuous frames per second to 3 fps. It is adequate but barely. Below is an image taken with live view from a blind.

Noise and Image Quality
 The Canon 7D has been maligned across the internet for its poor image quality at higher ISO and I can verify that this camera could be better in the area of unwanted noise, but I want to look at this subject objectively and explain to you that it is manageable. 
  At ISO below 320 I would say that you have absolutely nothing to worry about. Shoot away with little thought beyond achieving a good exposure. However, above ISO 320 and you need to start thinking about how to maximize your exposure to help mitigate noise. The first way to keep the noise levels down is obvious but I will mention it anyway. Shoot with the lowest ISO possible for the situation and lighting. If you are shooting a photograph of a building on a tripod with no movement then why shoot at ISO 400. Instead change your ISO to 100 and adjust your shutter speed and f-stop accordingly. Next, if you must shoot at ISO 400, 800 or 1600 you should use a process called "exposing to the right (ETTR)." I am not going into great detail about this process here but essentially you are overexposing the image by up to one stop in most cases. Later, in post-production, you bring the exposure and highlights into normal ranges.  The important consideration when using ETTR is that you don't want to blow out the highlights. You want to overexpose enough to reduce noise but still maintain the highlights. This is where practice and experience comes into play.  For more information about ETTR, navigate to this site: http://digital-photography-school.com/exposing-to-the-right/ .  
 Overall, I would say the image quality is quite good and on par with my 1D Mark II. The advantage to the 7D over earlier cameras is it's ability to render backgrounds smoothly without banding. This creates a much smoother bokeh and in my opinion a much more pleasing image. 
 My thoughts on auto-focus will be brief, but hopefully will shed some light on the subject for you. Auto-focus on the 7D is quite advanced with 19 cross-type AF points from which to choose. These advanced points allow the camera to lock onto moving subjects much faster than other APS-C cameras in the past and is a big reason to buy this camera. Using the AF under normal usage such as stationary objects with my Canon 50mm 1.8 I found the auto-focus to lock on so quickly that I couldn't tell when the lens had focused. It is fast and accurate and no issues here. When using my Tamron 70-300 SP VC I found it to also lock on and focus quickly with stationary subjects. Note that live view is much slower to focus because it uses a different auto-focus technology that is not part of the SLR portion of the camera. Eventually I believe the live view focusing will catch up, but for now it is not very useful when photographing wildlife. When I use it from a blind I generally use pre-focusing techniques. In the field I was a bit disappointing in the auto-focus. I was able to get a few in focus shots of turkey vultures on a recent trip to pilot mountain but I didn't get anything good enough to post here. Hopefully I can return to this location in the future and provide some followup as to whether the problems I found were related to my lens or the body. To be fair, I am also comparing this to my 1D Mark II's auto-focus system which is very very good.
Cost/Benefit Analysis vs Canon 7D Mark II
If you are like me, you are constantly balancing cost of new equipment versus what benefit the added cost will do for you.  For me, I am always looking for cameras and lenses which are about 1 generation behind the current models.  The reason for this is because cameras are essentially computers and as such they depreciate quickly.  Currently the Canon 7D can be purchased used for about $600.00 US , but when it was introduced cost about $1,700.00 US.  In other words, buy used if you can because it will save you a ton of money and you still benefit from all the features of a modern DSLR.
It is true that the 7D Mark II has a few more bells and whistles but most "experts" are reporting only a marginal increase in image quality.  For me, I would rather put more money into glass than have a few more features on my body.  On the Mark II we pickup a couple more frames per second continuous shooting, more cross type sensors and the ability to auto-focus at f8 with the center point.  Additionally we get a duel card slot for backup.  The 7D (classic) can shoot at 8fps which is more than enough for action photography. Auto-focus is slightly behind the curve, but still very powerful.  If the Mark II had achieved remarkable increase in image quality I think more of an argument could be made to upgrade.
In conclusion, the 7D (classic) remains a great camera which will continue to provide great results for years to come.  For me it was a modest upgrade on image quality, but 18 megapixels gives me room to breathe on cropping and the live view gives me more options when photographing from a blind. I picked up more of a crop on my images so using a tele-converter is no longer necessary. The benefits from upgrading from my Canon 1D Mark II was well worth it.  If you are looking for a camera with a crop sensor for wildlife I feel I can recommend the Canon 7D.