SteveL54

Lives in United States TX, United States
Works as a Engineer
Joined on Apr 2, 2004

Comments

Total: 3, showing: 1 – 3
In reply to:

SteveL54: Thanks for the fine article

I just completed intermittent illumination test on Canon 20D with EF 50mm f/1.4 lens. Used a Nikon SB-800 off camera as the light source. The target has very bold black & white lines of irregular width running horizontally. The center AF point was used.

I set up as you specified except the camera was almost 6 feet away from the target (not very near MFD). I could not disable focus search.

I repeated the steps several times. In all cases, when I had the room very dark, two flashes were needed for focus confirmation. ( At higher room lighting level -- but still low -- I had one test cycle that took three flashes. Another cycle took just one, but it's photo was OOF.)

On a few of the cycles I looked at the lens distance scale after the first flash and it had always reached the correct focus distance. On second flash focus confirmation was made and if I had the button fully depressed it took the photo (exposure was several seconds at f/2 and ISO 800)

Steve

I had time early this afternoon and was curious about the Squirrel Test. The AF behaved as you would have expected.

As soon as I initiated AF on the near subject I could see the AF moving into focus on the near subject. But right after quickly panning to the background, focusing direction reversed and stopped on the background with confirmation.

I tried it several times the other way with consistent behavior. Focus would start to move towards the background but reverse towards the forground target once it was swung into the center AF point.

Both near and far targets where directly illuminated by the sun. Near target about two yards away while far target was about 20 yards. Near target a tree trunk with good texture and the far target a mix of brush and small tree trunks. The 20D AF system reliably and smoothly aquired focus lock if I dwelled on the targets so they are both good targets.

I used an EF 50mm f/1.4 lens and a 100-400 L IS. (IS off)

Steve

Link | Posted on Oct 29, 2011 at 18:58 UTC
In reply to:

SteveL54: Thanks for the fine article

I just completed intermittent illumination test on Canon 20D with EF 50mm f/1.4 lens. Used a Nikon SB-800 off camera as the light source. The target has very bold black & white lines of irregular width running horizontally. The center AF point was used.

I set up as you specified except the camera was almost 6 feet away from the target (not very near MFD). I could not disable focus search.

I repeated the steps several times. In all cases, when I had the room very dark, two flashes were needed for focus confirmation. ( At higher room lighting level -- but still low -- I had one test cycle that took three flashes. Another cycle took just one, but it's photo was OOF.)

On a few of the cycles I looked at the lens distance scale after the first flash and it had always reached the correct focus distance. On second flash focus confirmation was made and if I had the button fully depressed it took the photo (exposure was several seconds at f/2 and ISO 800)

Steve

With the 20D I wasn't sure what to expect. I don't use it as much as my Nikon gear.

From tests carried out a few years ago on my Nikon D70 and D300 I was sure they are closed loop under low light conditions or if the target is particulaly challenging. The multiple movements under these conditions are fairly obvious.

I haven't tried the Squirrel Test. (It was too dark to take advantage of the long focus travel distances outdoors. Besides all the neighborhood squirrels were asleep.) The Squirrel Test can test the system under normally bright light conditions when the system *might* normally operate in a mode without the terminal focus confirmation measurement.

I don't know if I can get to it this weekend, so if anone else with a 20D and the time is curious I'd be interested in their results as well.

Steve

Link | Posted on Oct 29, 2011 at 13:43 UTC

Thanks for the fine article

I just completed intermittent illumination test on Canon 20D with EF 50mm f/1.4 lens. Used a Nikon SB-800 off camera as the light source. The target has very bold black & white lines of irregular width running horizontally. The center AF point was used.

I set up as you specified except the camera was almost 6 feet away from the target (not very near MFD). I could not disable focus search.

I repeated the steps several times. In all cases, when I had the room very dark, two flashes were needed for focus confirmation. ( At higher room lighting level -- but still low -- I had one test cycle that took three flashes. Another cycle took just one, but it's photo was OOF.)

On a few of the cycles I looked at the lens distance scale after the first flash and it had always reached the correct focus distance. On second flash focus confirmation was made and if I had the button fully depressed it took the photo (exposure was several seconds at f/2 and ISO 800)

Steve

Link | Posted on Oct 29, 2011 at 03:06 UTC as 8th comment | 4 replies
Total: 3, showing: 1 – 3