Originally Posted by neuroanatomist
Is the overhead light your only light source? If so, is the LensAlign positioned far enough back so the focus target is well-lit? Here's the setup I use for longer focal lengths, where I need the target near a wall so I can set up the camera up to 32' from the target. There's a light shining down onto to the ruler so that's illuminated (the side light on a Tiffany torchire lamp, in this case), but also notice the gooseneck light pointing at the LensAlign from the front for a bright, even illumination of the focus target plate.
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I set it up several diffrent ways. One of the locations I noticed later I was getting uneven lighting on the ruler portion. So I discarded those results. One way I had good lighting from the windows. Two others I set up directly underneath overhead lights. The last place I used was in my living room, setting up directly underneath the overhad ceiling fan fixture. Of course the fan was turned off so there was no vibration. Then I turned on selected lights in the halls, other rooms and tried to keep the same lights on continualy. I reset WB to K at 3200 so that it was about right for ambient.
I thought about buying some cheap tungsten lights to brighten the rooom, but for the 35mm and 24mm the lighting I am using right now is probably going to be very similar to the situations I want the AF to be accurate in. Outside shooting and landscapes the AF usally isn't going to matter as much.
I think some of the problem was lighting and it was causing slight variations. This is good info to know, even though it doesn't affect it much it seems toaffect some.From now on I will just be consistent from one test to the next and do each the exact same way.
I am thinking that possibly just the act of just changing the AF adjustment over and over can create a little diviation. So what I am going to do from here on out, is establish the actual value I want by running through the scale once or twice and then retest just that single point value several times over the course of the next few days just to verify it is consistent. If it seems like it is off I can just go up or down 1 and recheck again later. I did this last night with both lenses. I took a series of 20 pictures with both lens, which are mounted on seperate cameras. Rather than trying to determine a exact centernumber on the scale(which is kind of hard with these wide lenses) I just logged Front Focus, Dead On and Back Focus. The 35mm F1.4L tested exactly the way it had been the night before, it came up with 3 FF, 4 DO, and 14 Slight BF which is what I wanted (I may adjust this by one if I feel the bf is to much). The 24MM came back 7FF, 4 DO, 10 BF and its test was consistent with the day before. So far from one day to the next the results at just that AF adjustment location appear to be consistent. I am going to recheck this over the next few days to see how it fairs.
(Side Note: I really haven't comared the two as I had no need because they are diffrent focal lengths. But the 35mm F1.4L and the 24mm F1.4L II are sister lens with the same similar body (which I already knew). But side by side the last few days I the II version of the 24mm F1.4L puts out better looking pictures than the 35mm. The color and contrast arenoticablybetter on the 24mm. Not that the 35mm isn't an awesome lens, it is, I would like to see the updated 35mm F1.4L IIvesrion some time in the future)
Thanks for the help
Rick
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