In my August 30 post, "The Value of Experience," I said I'd tell interested parties how to make a low-cost diffuser for portable flash units. If you're interested, what follows are detailed instructions and photos showing how I do it.
How sharp is sharp enough? Sharp as a thorn? Sharp as a tack? Pin sharp? I say if it looks sharp, then it is.
Around three weeks ago, Dave Etchells of SLRGear.com published an article titled "Focus Falibility: Lens Test Fallacies." I'd link you directly to the article, but it's a Javascript page. Click the link above and you should be able to find it easily enough. Anyway, the basic point of Dave's article is that for any given lens it can be extremely hard to determine the point of exact focus and thus the point of maximum resolution. To take it one step further, Dave claims that the chances of either you or your camera being able to determine the point of exact focus are slim to none. A bit unnerving, eh?
Read carefully, however, and you'll discover that, according to Dave, the visual difference between "exact" and "pretty damn close" is barely detectable, especially in the center. The edges of the frame are a different story: Minuscule differences in focus can make a major difference in corner resolution. So does this mean you should look for lenses with the flatest field possible?
Personally, what I get from all this is that while exact focus can make a big difference in how well a lens performs in a test, it makes a questionable difference in real world photographs. After all, most photos are of three-dimensional objects, not two-dimensional test charts. Tests are done with the camera mounted to a tripod or optical bench. Real photos are often taken hand-held. Test results are inspected at resolutions equaling a 20x30-inch print. Real photos are often printed no larger than 8x10 inches.
Does this mean I think lens tests are worthless? Not at all. What I do think is that we should concern ourselves more with a lens' actual performance than its theoretical performance. If it does what you need it to do, then that's all that really matters. Another lens might theoretically be better, but then, we might theoretically be a lot better photographers than we actually are, right?
One of the challenges of today's digital age is that you can read your camera's instruction manual six times from cover-to-cover and still not understand how your camera really operates. In some cases its because the manual may tell you how to do something but says little about why you might want to do it or when. In other cases its because certain features aren't fully documented. You have to actually use the camera, try things out, and take careful notice of what it does and doesn't do.
Here's an example from the Canon EOS 10D, 20D, 30D, 40D series cameras: Whatever you set the camera to in Manual mode will stay that way, even if you switch exposure modes. Set the camera to 1/125 at f/16 in M mode and even if you switch to AV, when you later switch back to M, the camera will still be set to 1/125 at f/16. This fact isn't mentioned in the instruction manual, however; I had to discover it on my own.
"So what?" you ask. Well, suppose you were shooting outdoors on a bright sunny day. You could set your camera for the correct exposure in M mode and know that every object lit by direct sunlight would be correctly exposed, even if some of it was in deep shadow. If you went indoors, you could switch to one of the auto modes. When you went back outside you could switch back to M mode and as long as the sun was still shining brightly, you wouldn't have to reset the exposure. (This assumes you didn't also change the ISO, of course.)
I have no idea whether other DSLRs work this way. The point is that unless you take the trouble to develop an intimate knowledge of how your camera operates and how to put these features to good use, then you're really only getting a fraction of its full value. So, what cool but poorly documented features have you discovered about your camera? If you care to share, be sure to mention the camera as well as the feature. I'm sure I'm not the only one who'd love to know how to expand my horizons.
Digital Photography Review (aka DP Review) recently posted an image gallery of photos from the new-but-not- yet-available Canon EOS 1000D. What I found interesting was that of the 30 photos in the gallery, 13 were shot with a Sigma 30mm f/1.4. The rest were shot with an assortment of Canon lenses, but overall, photos taken with the Sigma were in the clear majority. If you're the sort of person who prefers to look at real-world photo samples instead of test charts, I suggest you check it out. If you'd prefer to see more examples I shot myself, you'll have to wait a few more days until I can post them to my own web gallery. I'll do my best to post them this weekend. Enjoy!
