Im Cheap--Do-it youself AFMA Contraption

[neuroanatomist]

Yes, Rick, the long ruler kit for the MkII comes with the bigger target, too. Not sure if it attaches magnetically like the Pro version we have, though.

[HDNitehawk]

John

I deleted that post, I went to lensalign's website to see what the deal was. It is indeed a larger target, and since it is a kit you can add to the mark II, it is most likely a magnetic plate just like ours.

For what it is worth this is lensalign's website:
http://michaeltapesdesign.com/lensalign.html

[bob williams]

Thanks All for your comments. I finally had a chance to go out and test this thing this weekend and here is my assesment of this cheap alternative:

I took great care in insuring that the target and the camera were carefully aligned---Identical height, perpindicular, Level etc. I ultimtely used a laser level that would shoot across my backyard. I also took great care in making sure camera adjustments were correct, i.e. Wide open aperature (F4), ISO 100, MLU, remote triggered etc.

Using the 500L, I set up at a measured distance of 75 ft from the target. At this distance the target seemed to be almost perfect in that the black and white intersection was just enough to cover the center AF Point and still fully view the ruler along the left side of the frame. Since I was fairly sure my camera/lens combo was front focusing, I shot 10 images at 0, +5, +10 and +15 each. I then uploaded the images into LR for review.

Upon review, My front focusing suspicions were confirmed and this is where it became very difficult to judge. With a depth of field of about 11 inches it was very difficult to tell where the in-focus started and where it ended with any level of accuracy. I also noticed that over the 10 shots, the readings were not consistant so I went with what the majority of shots indicated. Ultimately, I decided that the +10 setting was the closest. Not happy with the lack of accuracy at 75 ft, I moved the camera to 37.5 feet and repeated the test. This became much easier with the depth of field cut to approximately 5 inches. AT this distance I was able to confidently narrow down the settings between +10 and +15. I again repeated the test at +10, +11, +12, +13, +14, +15 (10 Shots each and determined that +12 was my best set---but there was still considerable doubt.

One of my biggest problems wasn't the target but instead, the ruler. It just didn't seem to have enough detail to make assesments that I was confident of.

I haven't tested this with smaller lenses and narrower depth of fields yet, But with long lenses, I am skeptical of this devices accuracy simply because the ruler just doesn't have the detail to make solid judgements.

So, Unfortunately, I don't think my $5 device can provide the level accuracy that the $150 device can, but that it can get you close if you you don't have or are unwilling to spend $150.

I will probably spend the $150 to be confident in my lens accuracy. But, It was certainly worth the effort to explore this alternative.

Thanks again for all your comments.

[HDNitehawk]

Bob

Don't give up yet. Some of the problems you have with your set up you will have with the lensalign.

A couple of things, the large target on the lens align is 5 3/16" square. The farthest the edge of the ruler would be from your focus point would be 2 5/8". I think your ruler is to far from your target. That will exaggerate whether you are off if you are just a little bit out of square.

Next, forget testing at the longer distances. With the 500mm lens if it is dead on 37.5' you are going to be dead on at 100'.

Now for your results, it took me a while to really figure out how to read the ruler with the lensalign the easiest. Some times the results are obvious. But results will are never consistent. How I do it is find the farthest numbers out that are in readable focus both back and foward. I take at least 20 pics at a particular setting. I use 1 star for front focused, 1 for dead on and 1 for back focus. I also take several pictures in live view focused at 10x to give me a template of what it should look like. I use the template to decide the numbers I will be reading.

After I download the pics I put them up on full screen. Then I literally scroll through the pics judging them and assigning stars, rather quickly as I do not pick over each one. For example at +4 on my 300mm I came up with Front Focus 18 On Focus 17 Back Focus 18. This seemed to be the best average as I went higher to +5 and lower the results would shift accordingly. (keep in mind when I say front focus or back focus, the lens is probably still within tolerances and whatever you are shooting is falling inside your DOF).

Focus is never dead on each time, and if you try and determine the absoulute zero focus point it may drive you crazy. I found it extremely tedious to do it that way.

One other thing you might do, is set up a flash on your ruler remotely. If not a flash run a light out to it and put it where it lights the ruler.

So I see at least two things to change. Get your focus point closer to the ruler. Make sure you have enough light on the ruler. Possibly change to a white ruler if that doesn't do the trick.

[bob williams]

So I see at least two things to change. Get your focus point closer to the ruler. Make sure you have enough light on the ruler. Possibly change to a white ruler if that doesn't do the trick.

HD, Thanks for the tips. I ran out of time this weekend, but will defintely try your suggestions before dropping the big bucs.

I'll let you know how it goes.

Thanks again