On Mar 9, 2013, at 5:51 PM, Stan Halpin wrote: > Apologies in advance for what may be a dumb question(s) . . . > Are all of these tests using autofocus?
Yes, all of them were with autofocus. > Assuming yes, then > - You say the focus target was the focusing chart. Did you use the > viewfinder and/or liveview to verify that the system was focused on the > target? And not on the numbers on the ruler or some other point? I mounted the camera on the tripod. Selected the focus point on the focus chart. IIRC, it was the upper right focus point. I did not reset the focus point, but I would put my hand in front of the lens. and touch the shutter to get it to defocus. I then pressed the shutter, the camera would focus and then take the photo. I heard the focus motor whir. For each lighting set up, I'd repeat several times. For each lighting setup I'd adjust the shutter speed based on the histogram. Auto exposure in monochromatic light results in one channel being blown out, and two channels still being way underexposed. > - What happens with the same setup if you manually focus? I didn't try that. This was actually about the third or fourth series I ran. On the first set, I had center focus, centered on the focus chart. The plane of the focus chart was even with the wig dummy's eyes. http://www.flickr.com/photos/ellarsee/sets/72157632961487174/ or http://www.fluidr.com/photos/ellarsee/sets/72157632961487174/ > I am trying to grapple with what are the possible failure points in the AF > process . . . I kept hearing about the problems with K-5s front focusing in tungsten light. Usually, when I have problems with front focusing, it is tungsten light, but there is also a microphone in front of the subject, even if the focus point is on the other side of the screen. I tried to come up with a quick experiment that I could do that would shed some light on the issue. I don't have the time I need to properly investigate the issue. One thing that should be done would be to set up a focus chart, and have a yard stick going diagonally across the screen to get a better feel, and quantification, of front and rear focus. What I expected was that red would front focus and blue would rear focus, but that didn't seem to be the case. It would be interesting to do an experiment with light levels and focusing. It is possible that the front focusing has more to do with light level than it does with color temperature. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
