AFMA methods; software vs. manual contraption vs. "winging it"

[Scott Stephen]

Hi,

Just bought a camera body with AFMA, and naturally thoughts turn to using it. I wonder a bit about my new 85mm f/1.8 in particular. Though I know that shallow DOF will test one's shooting technique, it seems to "hit" a bit less than my cheap old nifty fifty. I'd like to know if it is right, and if not to fix it (and all my other lenses too.)



1.) Some people still advocate the "old school" idea of tacking a newspaper on the wall and using that. Valid?



2.) The Spyder LensCal looks pretty straightforward. (So much so that I wonder if I could make one with a ruler and a shoebox, actually). Has anyone used that, and what do you think of it? http://www.bhphotovideo.com/c/produc...ation_Aid.html

http://www.the-digital-picture.com/R...al-Review.aspx

I would not mind spending the $62.00 for the convenience of not trying to rig something up myself, provided that it is in fact convenient, and accurate.



3.) The FoCal "automatic" software system looks kind of neat.

http://www.youtube.com/watch?v=veyBmZbt7AY

Some commenters say it works, others either can't make it work, or struggle a lot longer than I would ever want to. You have to shoot tethered, though? My computer is set up in a room too small to achieve those long shooting distances. The wife got an I-Pad for Christmas. Maybe I could use that. Anyway, are all those multiple shots and the bell curve plots, etc., really useful or helpful as compared to the simpler "manual" method with the Spyder device? Time saver, or big pain?



4.) None of the above? Any better thoughts?


Thanks for any input!

[herbert]

Hi Scott,

I've tried using a home made device (perpendicular target and angled ruler) and the moire contrast interference approach:

http://1000wordpics.blogspot.co.uk/2...moire.html?m=1

Both were inconsistent. I now use Focal and find that the computer does a lot of the hard work. The key is to have the target setup perpendicular to the lens axis, have a good stable base (so no movement) and to have good illumination. The software will tell you the Exposure Value (EV) so you can see how well the target is lit. I use a couple of spotlights. The stable base is very important. If people are walking around on the floor it will throw out the consistency of the measurements.

The AFMA is not really relevant for walk around shooting since the aperture is not used wide open and the depth of field covers focus errors. It has improved my keeper rate when shooting wide open telephoto lenses: 200mm f2.8 and 400mm f5.6.

Alex

[DanK]

Scott,

I agree with Alex. I have used the typical small target at 45 degrees (really too close for a good test unless you are going to be shooting that close), the moire contrast technique, and FoCal. The all agreed: 4 of my 5 lenses are just fine. one called for a small adjustment, but as Alex said, a small adjustment only matters if you are shooting nearly wide open, and I frankly have not noticed a difference in actual use since adjusting it. OOH, I was lucky--some people find that they need a lot of adjustment.

Having tried all three, I am partial to FoCal. It is very easy to use. I taped the target to a wall and illuminated it with two halogen floods. That worked fine. It showed me that the AF in my camera is somewhat unreliable in the statistical sense--more variation from one try to the next than I would like. BTW, I needed help with something, and their customer service was very good.

Dan