lens calibration


royd63uk

Link Posted 14/02/2011 - 13:04
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
regards
Roy

Pentax K3 gripped,and some lenses
https://www.flickr.com/photos/pentaxroy/

my pbase gallery

mujirushi

Link Posted 14/02/2011 - 13:21
I suppose this is what you are looking for =)

http://focustestchart.com/focus21.pdf
Still learning!

Zooms: DA12-24 | DA16-45 | DA*50-135 | DA55-300
Primes: FA31 | DFA100WR | M50F1.7
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xbow

Link Posted 14/02/2011 - 13:48
Or this one:

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

Vic.
K5, LightRoom 5
Sigma 8-16 Pentax DA 16-45 Pentax DA 55-300 Pentax 18-55WR Tamron 90 Di Macro Metz 44 AF-1

royd63uk

Link Posted 14/02/2011 - 14:17
thanks have printed both off
regards
Roy

Pentax K3 gripped,and some lenses
https://www.flickr.com/photos/pentaxroy/

my pbase gallery

Smeggypants

Link Posted 14/02/2011 - 15:26
mujirushi wrote:
I suppose this is what you are looking for =)

http://focustestchart.com/focus21.pdf

This is the one I use


Or you can use a tape measure
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Last Edited by Smeggypants on 14/02/2011 - 15:26

thoughton

Link Posted 14/02/2011 - 15:27
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?
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
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Smeggypants

Link Posted 14/02/2011 - 15:32
thoughton wrote:
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]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

Mike-P

Link Posted 14/02/2011 - 15:37
I use 5 clothes pegs on a washing line.
. My Flickr

johnriley

Link Posted 14/02/2011 - 15:48
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?
Best regards, John

Algernon

Link Posted 14/02/2011 - 18:02
Smeggypants wrote:
thoughton wrote:
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'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.
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

xbow

Link Posted 14/02/2011 - 18:40
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.
K5, LightRoom 5
Sigma 8-16 Pentax DA 16-45 Pentax DA 55-300 Pentax 18-55WR Tamron 90 Di Macro Metz 44 AF-1

Joe S

Link Posted 14/02/2011 - 23:02
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?
Hi. My name is Joel and I'm a travelholic.
Stolen kit: Pentax K7 #3428965 and Pentax FA 43mm #0028350

Smeggypants

Link Posted 14/02/2011 - 23:47
xbow wrote:
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.





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]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

Crossed-up

Link Posted 14/02/2011 - 23:57
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.
My Images
K1 II|K3|DA10-17|DA*16-50|FA31|DA*50-135|DA*200|DA*300|Sigma 150-500

royd63uk

Link Posted 15/02/2011 - 09:06
Quote:
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
regards
Roy

Pentax K3 gripped,and some lenses
https://www.flickr.com/photos/pentaxroy/

my pbase gallery
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