SCPG Forums

[a.hoglen]

Well since I have nothing creative in me this week, I decided that I'd cal my lenses to both my bodies...

There are a few ideas on how to go about this, so I'll just post what worked best for me. I also don't have any technical knowledge about optics other than what little I've picked up by doing this for the last 1.5 years, but I have worked in electronics and calibration for over 10 years and applied a lot of the same theory to calibration to this shebang. I'm thinking I should set up a worksheet to help me keep up with the settings and see if they drift over the years.

I got a metal yardstick with standard and metric markings and set it up @ a 45deg angle to the camera. This allowed me to use both the larger standard scale for the wider angle stuff and the smaller mm scale for the tele's.

I set up my tripod and went to work. At first I started to set each lens individually until I was getting wide variances in settings. I realized I had not set my standard (default) yet. So, I went to my sharpest lens that never seems to miss focus, the 105mm 2.8 VR macro. I used this lens to set the default adjustment for the body. Then I went on to calibrate the lenses.

It is a little bit of guess work at first. For the zooms I set the widest angle first then make sure the other end is also in focus. Usually I had to make another adjustment at this point, and then checked the wide angle again. Then to be sure I checked a random point about the middle of the range. Primes were a lot easier.

I was using the viewfinder to check the tune. I'm sure shooting tethered or uploading the pics to a computer might yield a little better tune, but for me it wasn't worth the effort. To each his own, right?

The only issue I had was having to go back on the D700 to set the default to +10 so that I could get the Sigma 50mm 1.4 dead on...Big surprise. With that being done the Siggy is still around +18 fine tune. It is almost at the end of the scale. I'm thinking I should just send it back in because a new lens shouldn't be that far out.

Another interesting point is that on the D300 the siggy didn't seem as far off as it was on the 700. I think I ran a default value of +2 on the body and +6 on the lens. I'm sure it has something to do with sensor size and distance of element to sensor.

Pointers:
-Bright ambient light is your friend
-Set your default first. I used the lens that gave me the best warm and not so fuzzy to set it. It will save you time in the end
-Use a good tripod (seriously... throw the sunpack away or use it for a remote flash and get something substantial)
-Give yourself a good 2-3 hrs to do this. I did 2 bodies and 7 lenses on each body totaling 14 combinations.
-Turn VR/OS/IS off. You don't need it and it could/will affect accuracy results.


What do you think about these methods? Any more advice or input?

[Steve]

I think I would have HAD to shoot tethered to a PC. I think squinting for perfect focus for two hours would have had my eyes far too blurry for function.

I've been looking for an excuse to try out some of the free tethering solutions.... this might be my reason.

Advice on the solid tripod is well.... solid advice.

The technique sounds....sound.

[a.hoglen]

It's not horrible. I have the center button on the D-pad on the back set up to do 100% magnification. Using the ruler's mm marks it's pretty obvious if you are on or off.