Lens calibration shop


schnitzer79

Link Posted 28/05/2014 - 07:29
Hi everyone,

Wanted to know if there is a reputable shop that calibrates lenses for back focus issues (+10 on fine tune wont quite cut it).

Thanks

gartmore

Link Posted 28/05/2014 - 09:27
How you go about this is dependent to some extent on which camera body you have
Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

schnitzer79

Link Posted 28/05/2014 - 09:49
sorry i forgot to mention it.its for the k-50.plus i live in Cyprus so I was hoping I would be able to send in the lens alone without the body. camera is fine since all of my other lenses are ok.

the lens is the smc da 15mm ltd.it seems to be okayish at +10 but was wondering if i could get it even better with a shop calibration. I did the test with a focus chart yesterday at f/4 even though its really hard with such a wide angle lens to give accurate results.
well 95% of the time ill be shooting at apertures smaller than f/8 since i got this lens mainly for landscapes so maybe its not worth it after all. just would be nice to know if theres a decent shop in the UK so I can rely upon since I also come over once a year and could take the lens in then
Last Edited by schnitzer79 on 28/05/2014 - 09:59

johnriley

Link Posted 28/05/2014 - 10:00
There are repair houses in the UK and the official one is JPS. You could perhaps book your lens in in advance of arriving in the UK, or maybe send it ahead and then collect it while you were here.
Best regards, John

schnitzer79

Link Posted 28/05/2014 - 10:41
thanks john. ive emailed them now

Gamka

Link Posted 28/05/2014 - 17:42
Which part of Cyprus?

The main part of Cyprus is EU so there will be no issues of duty/VAT even though they can be legally avoided it can be a problem. However, if you are in Northern Cyprus you will need to deal with the issues before sending or you could get a nasty bill.

Smeggypants

Link Posted 28/05/2014 - 23:45
I've always wonder how lenses are calibrated. I've taken some apart to fix them and there doesn't appear to be any adjustments to alignment of lenses.
[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

Gravelrash

Link Posted 29/05/2014 - 00:52
Smeggypants wrote:
I've always wonder how lenses are calibrated. I've taken some apart to fix them and there doesn't appear to be any adjustments to alignment of lenses.

Obviously your hammer isn't big enough
Steve

Sometimes I'm serious and sometimes not, but I consider sarcasm an artform. Which is it today?

kh1234567890

Link Posted 29/05/2014 - 01:33
Smeggypants wrote:
I've always wonder how lenses are calibrated. I've taken some apart to fix them and there doesn't appear to be any adjustments to alignment of lenses.

It's all in software* - they just rewrite the look-up tables

* if by 'calibration' the OP means having the liveview focus the same as the phase detect focus and not having the lens so broken that it can't focus on infinity in liveview.
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dpm

Link Posted 29/05/2014 - 06:53
^yup.

Whilst lenses do have plenty of adjustment for centration and position of the internal elements, this is to do with setting the length and centration of the intermediate images. It will however affect overall sharpness and bokeh (this is the variance we see within batches).

It should not affect focus because- as per kh above- focus is about flange distance from sensor and AF module. Only if the helicoid hits its' stops before infinity focus is achieved is there an issue.

schnitzer79

Link Posted 29/05/2014 - 07:21
Hi everyone,

got an answer from JPS and told me to contact my nearest repair agent which ive contacted a few months ago for another problem and were totally useless.
I did fine tune the lens as i said to +10 on my k-50 which is the maximum,it seems kind of ok since i had to crop the image to check it properly.heres a before and after so you guys can help me out a bit. focused on the 0 in the 2nd column from the right at f/4.


Smeggypants

Link Posted 29/05/2014 - 07:25
kh1234567890 wrote:
Smeggypants wrote:
I've always wonder how lenses are calibrated. I've taken some apart to fix them and there doesn't appear to be any adjustments to alignment of lenses.

It's all in software* - they just rewrite the look-up tables

You can of course physically adjust the AF module ( with s screw underneath the bottom panel IIRC ) to place the lenses within the +/-10 parameters range on the camera's AF software parameter. That wouldn't use look up tables though as it's a physical adjustment. Given it's phase detect I would have thought some kind of comparator circuit would be used to detect Focus. The AF parameter could use look up tables to avoid a real time calculation if the numbers aren't linear in proportion to the actual compensation required, ut I can't see this being the case.


However I'm talking about calibrating the lens itself, not the camera.


dpm wrote:
^yup.

Whilst lenses do have plenty of adjustment for centration and position of the internal elements, this is to do with setting the length and centration of the intermediate images. It will however affect overall sharpness and bokeh (this is the variance we see within batches).

It should not affect focus because- as per kh above- focus is about flange distance from sensor and AF module. Only if the helicoid hits its' stops before infinity focus is achieved is there an issue.

While I am interested in how these centration and position of elements are calibrated ( something else that has elided me ), I'm also interested in how the lens itself is calibrated to allow the cameras AF calibration to be more accurate.

I know from experience that different lenses, even different copies of the same model lens can need different AF settings in the camera but I still cannot work out why. If the distance from the flange to the main sensor and the distance to the AF Sensor is exactly the same then in theory the AF should be accurate for any lens attached to the camera.

But it's not. I can only assume that aberrations in each lens makes the difference, so ergo reducing those aberrations by physically more accurately aligning the lens elements should result in a smaller compensation value if at all being needed to be dialled into the camera.
[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 29/05/2014 - 07:33

Smeggypants

Link Posted 29/05/2014 - 07:36
schnitzer79 wrote:
Hi everyone,

got an answer from JPS and told me to contact my nearest repair agent which ive contacted a few months ago for another problem and were totally useless.
I did fine tune the lens as i said to +10 on my k-50 which is the maximum,it seems kind of ok since i had to crop the image to check it properly.heres a before and after so you guys can help me out a bit. focused on the 0 in the 2nd column from the right at f/4.



I can see +10 still isn't enough. What AF settings do you need for your other lenses? Of they are mostly in the plus range then it's likely the AF Module in the camera will need adjusting physically ( screw underneath the bottom plate in other Pentax models I've seen )
[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

schnitzer79

Link Posted 29/05/2014 - 08:03
all my other lenses are fine but its been a while since i checked them with the focus chart. which number do you see in focus on the picture in the right?because for me both 0 and the 8 above it seem ok whereas 16 isnt (referring to 2nd column fm right again)

Smeggypants

Link Posted 29/05/2014 - 09:10
schnitzer79 wrote:
all my other lenses are fine but its been a while since i checked them with the focus chart. which number do you see in focus on the picture in the right?because for me both 0 and the 8 above it seem ok whereas 16 isnt (referring to 2nd column fm right again)

-8 looks sharper than +8 here so it's still slightly back focussing.
[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
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