You have some nice photos in your gallery, and your 28-135 looks like a good copy. Having said that, the 70-200 f/4 L IS is a significant step up from this lens, and is probably the best zoom Canon has ever made in terms of image quality.
What you lose with the 70-200 f/4 IS compared to a f/2.8 IS:
DOF – the f/4 will not be as shallow wide open, this can be either good or bad depending on the shot, but generally it is not a problem.
The 40D autofocus switches into a higher accuracy mode when an f/2.8 or faster lens is mounted, 1/3 DOF for a f/2.8 vs. 1 DOF for smaller apertures. Not a problem as the 40D AF accuracy seems to be quite good to begin with.
Shutter speed or ISO – You lose 1 stop, for most shots this should not be an issue as the 40D can shoot quite well at higher ISOs, and for daylight, flash & other moderate to well lighted work f/4 is fast enough, and this lens can be used wide open. Where the f/2.8 shines is low light photography, where the ISO is already pushed to its limit and you still need a faster SS. However the price to gain the extra stop is very high. Photos at dusk are a challenge, especially if it’s sports related with subjects in motion. The 1 stop gain of the f/2.8 will certainly help, but you may need an even faster lens, and this would be a fast prime.
On the other hand, the f/4 version is very sharp wide open, while the f/2.8 has a tendency to be a little soft. Most folks don’t consider this to be an issue, unless you spend a lot of time examining individual pixels on a PC monitor. The f/4 has the latest IS, which is good for 3-4 stops in hand hold ability, compared to 2-3 stops with the f/2.8. the f/4 is smaller, lighter, and less costly as mentioned in a previous post.
IMHO, the best lens for you is the 70-200 f/4 IS. It will be very good as a general purpose zoom, good for drag racing, football and for portraits. It is so sharp it will show every wrinkle, pore, nose hair and skin blemish in well defined detail with portraits. Not a problem if you’re shooting cowboys, but if you want to stay on the good side of your female friends, you’ll need to do some post processing to soften the rough spots and maybe correct the bright spots that have too much light.
Prinothcat recommended a good WA lens for you to consider and look at. Something else you can do is check PBase. There is a great feature in that you can search for images by camera or lens (after the camera listings). I suggest you make a short list of the top lenses you are considering and check out some of photos. This should give you some realistic, real world examples. A couple of other resources, these with reviews:
http://www.photozone.de/reviewshttp://www.photodo.com/category_2.htmlAt the end of the day, you will have done your homework, probably have a short list of a few lenses, and are going nuts trying to pick the best one. Welcome to the club. Your significant other will be supportive, smile a little less when you mention ‘lens’ and your dog/cat now thinks ‘wide angle’ are bad words. Pick one and go for it, and it’ll be a good choice. The nice thing about lenses is you can always sell them if want to make a change.
I don’t have experience with the various in-camera shooting styles, and how much processing they do, I do all of this outside of the camera. You can explore and try them to see if they meet your needs. You should consider some photo editing software so you can make image-specific adjustments on your PC. There are many programs that will do this, some for free and some for fee. Adobe is probably the leader, I started with Photo Shop Elements and moved to the full version and it works for me.
You’ll see a number of posts from experienced users on different photo editing programs. They’re all good, each with its particular strengths and weaknesses. Elements is a good starting point, and will probably be enough for most photos.
RAW vs. JPG – I suggest you start with JPG and get the 40D experience with composition, exposure, ISO, aperture, etc. After you’re comfortable you can try RAW, IMO its main strengths are recovery of *some* blown highlights (about 1 stop of headroom), and correcting white balance if needed. There are a few other areas it’s helpful with, but for me those are the key ones. If you’re bored on a rainy day you could start to experiment with RAW. You’re using Canon DPP already, and it includes a very good RAW converter.
As a minimum, you need a backup CF. Quality, name branded CFs are cheap today. I suggest you buy from a reputable source and avoid ebay, etc. There are a lot of counterfeit CFs on the market.
Apologies for the not-so short story, I hope this is helpful and it is only my opinion. I hope others will add to the thread.