Archived posting to the Leica Users Group, 2000/11/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]The obvious answer is that a slightly out of focus image..... which is what you will normally get shooting wide open with an AF camera .... will not and can not resolve as much as a completely in-focus image... POP photography did a test on it with different systems a while back showing just how much difference there is between an AF camera in AF mode and the same camera and lens focused manually. Kind of scary actually. I should add this bears out my personal experience..... I get far better results manual focusing my EOS 1n than relying on AF..... I use a 70-200 f/2.8 for portraits and often use it at near 200 at f/2.8 or f/4 to blur out the background... with AF I was getting pictures where the focus point was often behind the eyes or on their hair etc... everywhere but the eye.... If you want a really bad looking portrait.... take one where people's ears appear sharper than their eyes... or their forehead is critical sharp but their eyes aren't..... anyhow.... you might not notice the cheek or nose is sharper than the eye as much with a shorter lens at a greater distance and a small enlargement.... But it is probably there. So.....I' personally have stopped using AF for all of my day to day work as I've been burned too many times with it. I've been tempted numerous times to ditch EOS altogether.... If you want to see it for yourself, switch your AF to MF and find some text somewhere about 4 or so feet away ... start with the lens at a closer focus setting and focus the lens slowly until the AF light comes on...... (As I've just done this again with the 28-70L here in my office...) The AF light comes on before the text is anywhere near perfect focus and I can visually see the image go out long before the AF light goes off again. Don't take my word for it.... do it yourself and you'll better understand why AF AF can't resolve as much as MF AF can and why AF AF it is near useless for critical work or situations where DOF can't cover it's inaccuracies Duane Birkey HCJB World Radio Quito Ecuador Duane's Photographs of Ecuador http://duane_birkey.tripod.com Martin Howard wrote: Now, I could go into saying that I understand how this explains grave focussing errors (hunting) on the part of AF systems, but not how you can get higher lp/mm from MF lenses compared to AF lenses, but I won't... ;)