Thanks for that. It's wierd to read your own old posts. Mine is # 17
For anyone using the 7D I found these essential reading:
http://photography-on-the.net/forum/...t-1134233.html. Particularly amfoto1's input which is so informative that I have again copied it in full just in case someone happens to come across this post.
"I've been using a pair of 7Ds for a bit over two years now and have had to learn how to get sharp images out of them... there are a few tricks.
1.Yep. The images are softer due to the strong AA filter on the sensor. Images require considerably more sharpening than any other Canon DSLR I've used (probably around 10 or 12 different models, over the years). For example, 50D have almost as much resolution with 15MP APS-C sensor, but I find 7D images need 40% to 80% more sharpening. The detail is hiding in there, and sharpening brings it out. RAW images in particular will require stronger sharpening. But even if shooting JPEGs, you may need to set stronger in-camera sharpening, unless you plan to apply it in post-processing instead (which might be a good idea if you plan to change the size of the image). I have not had opportunity to closely compare the other 18MP cameras (60D, T2i/550D, T3i/600D) with 7D... If they don't need as much sharpening, I'd just suspect they use a weaker AA filter and/or are applying more sharpening to the files in-camera. The other 18MP cameras came after the 7D and Canon might have "tweaked" the sensor and/or algorythms a bit.
2. If you have a filter on the lens, remove it. The very high resolution of the 7D is super critical of any flaws with lens or any optics in front of it.
3. Bump your shutter speed up... the high resolution of the camera also is more sensitive to even the least amount of camera shake. Canon has a white paper about this, on one or the other of their websites, that explains how the ultra dense sensors are more sensitive to slight movement. By default, I try to use 1/200 and 1/400 with 7D, where I use 1/100 and even slower with 5DII, 50D, etc. Note: The 7D sensor has more than twice the pixels per square mm than the 5DII's does.
4. Use an optimal aperture. Stop down a bit and don't be fooled by slight loss of sharpness that most lenses exhibit wide open. Depending upon the lens, f5.6 to f8 will usually give better results. But don't get carried away... Diffraction starts to set in with 7D's crowded sensor at around f7.1. That causes loss of fine detail which might be mistaken for "softness", too. You won't see it much at f8, very little at f11, but it starts to become apparent at f16 and smaller apertures. I suggest shooting a group of test shots with your particular lenses, of a highly detailed, flat subject (the classic brick wall or newspaper taped to a wall). Learn the optimal apertures of your particular lenses, and how much loss you can expect at larger or smaller apertures.
5. Between the need to use higher shutter speed and smaller apertures, you might need to use a higher ISO. I use 200 and 400 minimum usually with 7D. It also is good to do this because 7D's low ISOs are less noise free than some other cameras (but I find it's high ISO about one stop more usable than, say, 50D).
6. Be practical about your expectations. Particularly if coming from a significantly lower resolution camera, you might be in the habit of inspecting your shots at 100%, which is almost silly with a much larger image file from 7D. That's like looking at a 5 foot wide print from 18" away, viewing a 7D image at 100% on many computer monitors (even worse on lower resolution monitors). Will you really be printing the image that large and viewing it from such a close distance? Back off on the magnification. Also make an actual print... preferably with a good printer and on smooth, matte paper to see what you are actually getting. At best your computer monitor is around 96 pixels per inch, while most inkjets use at least 240 ppi and some printers use 300 or even 400 ppi. You might find yourself down-rezzing a 7D image to make a common print size, where you were having to up-rez it or print it at it's native resolution before, with a lower resolution camera.
7. Avoid underexposure, which makes for muddy images that tend to look soft. Also, contrast and the type of lighting being used can effect apparent sharpness in an image. Compact fluorescent lighting is becoming common, and is a pretty awful light source for photography. Common household types of fluorescent lighting even can cause focus errors... though it probably even more often causes exposure problems (due to the light cycling). There are photography-optimized/stabilized CFLs and fluorescent tube lighting available, but they are comparatively expensive.
8. Sure, use focus Micro Adjust to fine tune the camera to your particular lenses... but be aware of it's limitations. For example, you can only set one correction factor for a lens, and that might not be accurate across the entire range of focal lengths of a zoom. You probably should test a zoom at 2 or 3 different focal lengths, then either arrive at an average that's as close as possible or set a biased correction for whatever focal length you tend to use most with that particular lens.
9. There are different ways to do MA, too... Some may be more accurate than others, some folks might find one type of test more convenient and effecive to use than another... To be more or less repeatible. And be sure you are doing it right, at appropriate distances (for example, Canon recommends the target be 50X the lens focal length from the camera's image plane... so a 50mm lens would use a target that's 2500mm away, or a little over 8 feet). Use a tripod, make sure your target is parallel with the sensor or set up at the proper angle (depending upon the type of target and testing method you are using). To eliminate any possibility of camera shake, use mirror lockup and either a remote release or the camera's self timer so you don't have to press the shutter release button during the test.
10. Learn the focus methods and tweaks of the camera so that you can avoid some of the common focus errors, which make images look quite soft. The 7D's AF system is complex and highly customizable. This allows us to set the camera up for specific situations, to get very good results. But it also opens up many opportunities to set it up wrong and get worse results than we'd get with a "less capable" camera. Finally, stop worrying about it so much. Really... Go out and shoot, then make some prints. That's really what will show you how well the camera can do. No camera is perfect... I do get some small percentage of images ruined by missed focus or camera shake or general softness from atmospheric effects or flare... mostly "user error", but some of them are camera misses too, I'm sure. I throw those away... Clients never even see them. My percentage of "bad" shots has gone down considerably as I've practiced with the cameras and gotten better using them. I do editing and post-processing: Lightroom for quick edits & minor adjustments to make initial thumbnails, and Photoshop to more fully finish images prior to use. Now after a couple years using them, I've sold hundreds or perhaps even thousands of images made with 7D"
The articles/posts don't really deal with cars approaching but do help in getting control of your camera.