lens calibration

I think my 55-300 is front focussing,i think there was a chart you download from somewhere to test this,does anyone know where i can get it

I suppose this is what you are looking for =)

http://focustestchart.com/focus21.pdf

Or this one:

http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.h...

Vic.

thanks have printed both off

This is the one I use


Or you can use a tape measure

I use Yvon Bourque's one(the link from xbow above).

I'm always hesitant about using a tape measure. How can you be sure what the camera is focusing on?

Well the little red square in the view finder is pretty small. I assume that this point is the where the camera focusses.

I use the chart now but when used a tape measure it produced a calibration that worked.

I use 5 clothes pegs on a washing line.

Clothes pegs are a wonderful focusing aid. Attach string to peg, knotted at known intervals. Walk up to subject and attach peg to lapel or other suitable point. Walk back the correct number of knots, pull string to release peg.

Subject is amazed and smiles. You take picture, having preset the correct distance.

As for focusing tests, why not just choose a detailed subject, focus on it and see if it's sharp? You can forward and back focus slightly using QuickShift to check planes of focus just in front and just behind the subject.

I presume this needs doing at various zoom settings and various distances to average out any errors?

I've never found the little red square to be very accurate and the flat lens tests are pretty useless unless you stand something up vertical that you can actually focus on.

The expensive Lensalign is much better because it gives you a vertical target. The poormans solution is probably something along the lines of a Cornflake box with a 12" ruler on a 45deg ramp at the side.

It's also impossible to focus accurately by any means, every time so you need to take at least 4 shots and compare them.

I should have said that I don't like any that I've tried but looking at the Lensalign system it does look a better proposition:

http://67.18.178.219/videos/LensAlign.mov

I think I'll have to spend a few minutes drawing up something similar and making my own version.

Vic.

I have just done it - calibrated lenses all day using the mentioned lens chart. In support of Algernon's comment: No, the red square are not to be trusted so get something vertical in place to focus on! Also, if you print the chart make sure it is attached to something completely flat. When done, it is a lovely feeling that everything is optimized in the most scientific ways

Searching I found another method based on moire interference patterns. Didn't try myself. Anyone with experiences?

Over £100 - WTF!!!

I didn't consider a vertical surface would be better for focus. I can see why.


I could knock something up like the lensalign in about 20 minutes out of MDF.

In fact I will soon

I often use my computer keyboard leant at a 45 deg angle. I just focus on a specific letter key and check the image to see if the same key or the ones in front or behind are the ones in focus.

cool might try this too