Calibrating A Manual Lens.

tabl10s · 06-20-2014, 04:42 AM

Should it be done wide open or stopped down?

Last edited by tabl10s; 06-20-2014 at 08:24 AM.

stevebrot · 06-20-2014, 06:56 AM

What are you calibrating? Aside from adjusting infinity focus (not always possible), there is nothing to calibrate on a manual focus lens. Now if you are talking about calibrating the PDAF system against one of your manual focus lenses, that is another matter. I am not sure what you have in mind, but it is my understanding that per lens assignment of custom calibration is not possible for lenses that don't support the data contact (are not chipped to provide unique identification to the body). That would include all manual focus lenses that I am aware of. Confirmation would be whether the camera prompts for focal length on start-up. Chipped lenses provide that information. Non-chipped lenses don't.

It may be possible to assign a global setting and save that configuration as a custom user. In that case, you should do the calibration wide-open.

Steve

tabl10s · 06-20-2014, 07:15 AM

It's the A50 1.2. I guess nothing is needed.

ChristianRock · 06-20-2014, 08:45 AM

The only thing you should need to calibrate is your camera's diopter, if for some reason it's not where it's supposed to be

aleonx3 · 06-20-2014, 09:06 AM

Last time I sent my k-5 together with a bunch of lenses (mostly FA, DA but I did include a k 55f1.8 lens) to Pentax Canada repair shop for adjustment/tuning; this was done before warranty expires. They did all calibrations, lens and camera included except the manual k-lens. I think as long as the camera is within the -+10 tolerance, while using MF lens, then it will work (assuming you are using the camera's AF system to help with the focus using MF lens) or alternatively, as others have suggested changing focus screen or adjusting diopter etc.

tabl10s · 06-20-2014, 04:04 PM

Originally posted by aleonx3

Last time I sent my k-5 together with a bunch of lenses (mostly FA, DA but I did include a k 55f1.8 lens) to Pentax Canada repair shop for adjustment/tuning; this was done before warranty expires. They did all calibrations, lens and camera included except the manual k-lens. I think as long as the camera is within the -+10 tolerance, while using MF lens, then it will work (assuming you are using the camera's AF system to help with the focus using MF lens) or alternatively, as others have suggested changing focus screen or adjusting diopter etc.

I was using focus peaking. I tried different apertures for DOF then used it at 1.2. The adjustment seemed to work. I'm going to tien FP off and see I'd I get the focus indicator as on the K-5.

stevebrot · 06-20-2014, 07:49 PM

Originally posted by tabl10s

I was using focus peaking. I tried different apertures for DOF then used it at 1.2. The adjustment seemed to work. I'm going to tien FP off and see I'd I get the focus indicator as on the K-5.

Am I correct that you applied a universal calibration change based on the A50/1.2? The big question now is whether any of your AF lenses are in calibration.

Steve

timo · 06-20-2014, 10:14 PM

Originally posted by tabl10s

Should it be done wide open or stopped down?

As Steve said, what do you mean by 'callibrating'?

Not clear from your reply.

Tim

kh1234567890 · 06-21-2014, 01:30 AM

Originally posted by timo

As Steve said, what do you mean by 'callibrating'?

Presumably trying to get the thing to focus reliably, which at f1.2 won't be easy with the stock focus screen ...

tabl10s · 06-22-2014, 01:10 PM

Calibration to apply to one only. After trying 1.2, stopped down to 5.6 and higher.

**jbondo** · 06-22-2014, 08:44 PM

I've run into this phenomenon when calibrating infinity on the K50 1.2 (same optical formula as yours) and other fast lenses. When using highly magnified live view, there is the superficial impression that infinity is different for wide open (for example f1.2) than for one stop smaller (f1.4).

What is happening is that you can get fooled by the aberration wide open (typically the red channel) and instinctively try to optimize it so that the overall light spread is at the minimum. The problem with that is you are defocusing the green and blue channels trying to make the bad red channel better, and consequently make the overall MFT worse.

Try setting infinity using one stop less than maximum. This is easiest to do on a clear night using a white star as a point source. It may also help if you intentionally under or overexpose the image to better see what the abberations are doing and where the optimal point of focus is. Once you do this, verify that wide open and f8 are also acceptable and you should be good to go.

tabl10s · 06-24-2014, 03:06 AM

Should I use close objects also?

**jbondo** · 06-24-2014, 07:18 AM

No need to calibrate anything up close. The factory distance scale ring will be correct for shorter distances once infinity is calibrated.

tabl10s · 06-24-2014, 05:15 PM

Read long ago that infinity wasn't always the sharpest. I don't remember if this was the case just on one-touch zooms or it if included primes.

tabl10s · 07-08-2014, 05:40 AM

Originally posted by stevebrot

What are you calibrating? Aside from adjusting infinity focus (not always possible), there is nothing to calibrate on a manual focus lens. Now if you are talking about calibrating the PDAF system against one of your manual focus lenses, that is another matter. I am not sure what you have in mind, but it is my understanding that per lens assignment of custom calibration is not possible for lenses that don't support the data contact (are not chipped to provide unique identification to the body). That would include all manual focus lenses that I am aware of. Confirmation would be whether the camera prompts for focal length on start-up. Chipped lenses provide that information. Non-chipped lenses don't.

It may be possible to assign a global setting and save that configuration as a custom user. In that case, you should do the calibration wide-open.

Steve

I just found this on the LensAlign site:

Does LensAlign work for manual focus lenses? / LensAlign / Knowledge Base - Michael Tapes Design Support

06-20-2014, 04:42 AM	#1
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424	Calibrating A Manual Lens. Should it be done wide open or stopped down? Last edited by tabl10s; 06-20-2014 at 08:24 AM.

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06-20-2014, 06:56 AM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	What are you calibrating? Aside from adjusting infinity focus (not always possible), there is nothing to calibrate on a manual focus lens. Now if you are talking about calibrating the PDAF system against one of your manual focus lenses, that is another matter. I am not sure what you have in mind, but it is my understanding that per lens assignment of custom calibration is not possible for lenses that don't support the data contact (are not chipped to provide unique identification to the body). That would include all manual focus lenses that I am aware of. Confirmation would be whether the camera prompts for focal length on start-up. Chipped lenses provide that information. Non-chipped lenses don't. It may be possible to assign a global setting and save that configuration as a custom user. In that case, you should do the calibration wide-open. Steve

06-20-2014, 07:15 AM	#3
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	It's the A50 1.2. I guess nothing is needed.

06-20-2014, 08:45 AM	#4
ChristianRock Pentaxian Join Date: Jul 2013 Location: People's Republic of America Photos: Gallery \| Albums Posts: 9,912	The only thing you should need to calibrate is your camera's diopter, if for some reason it's not where it's supposed to be

06-20-2014, 09:06 AM	#5
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	Last time I sent my k-5 together with a bunch of lenses (mostly FA, DA but I did include a k 55f1.8 lens) to Pentax Canada repair shop for adjustment/tuning; this was done before warranty expires. They did all calibrations, lens and camera included except the manual k-lens. I think as long as the camera is within the -+10 tolerance, while using MF lens, then it will work (assuming you are using the camera's AF system to help with the focus using MF lens) or alternatively, as others have suggested changing focus screen or adjusting diopter etc.

06-20-2014, 04:04 PM	#6
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	Originally posted by aleonx3 Last time I sent my k-5 together with a bunch of lenses (mostly FA, DA but I did include a k 55f1.8 lens) to Pentax Canada repair shop for adjustment/tuning; this was done before warranty expires. They did all calibrations, lens and camera included except the manual k-lens. I think as long as the camera is within the -+10 tolerance, while using MF lens, then it will work (assuming you are using the camera's AF system to help with the focus using MF lens) or alternatively, as others have suggested changing focus screen or adjusting diopter etc. I was using focus peaking. I tried different apertures for DOF then used it at 1.2. The adjustment seemed to work. I'm going to tien FP off and see I'd I get the focus indicator as on the K-5.

06-20-2014, 07:49 PM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by tabl10s I was using focus peaking. I tried different apertures for DOF then used it at 1.2. The adjustment seemed to work. I'm going to tien FP off and see I'd I get the focus indicator as on the K-5. Am I correct that you applied a universal calibration change based on the A50/1.2? The big question now is whether any of your AF lenses are in calibration. Steve

06-20-2014, 10:14 PM	#8
timo Veteran Member Join Date: Nov 2006 Location: former Arsenal football stadium Photos: Gallery Posts: 431	Originally posted by tabl10s Should it be done wide open or stopped down? As Steve said, what do you mean by 'callibrating'? Not clear from your reply. Tim

06-21-2014, 01:30 AM	#9
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653	Originally posted by timo As Steve said, what do you mean by 'callibrating'? Presumably trying to get the thing to focus reliably, which at f1.2 won't be easy with the stock focus screen ...

06-22-2014, 01:10 PM	#10
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	Calibration to apply to one only. After trying 1.2, stopped down to 5.6 and higher.

06-22-2014, 08:44 PM	#11
jbondo Loyal Site Supportaxian Join Date: Sep 2013 Location: Texas Photos: Albums Posts: 503	I've run into this phenomenon when calibrating infinity on the K50 1.2 (same optical formula as yours) and other fast lenses. When using highly magnified live view, there is the superficial impression that infinity is different for wide open (for example f1.2) than for one stop smaller (f1.4). What is happening is that you can get fooled by the aberration wide open (typically the red channel) and instinctively try to optimize it so that the overall light spread is at the minimum. The problem with that is you are defocusing the green and blue channels trying to make the bad red channel better, and consequently make the overall MFT worse. Try setting infinity using one stop less than maximum. This is easiest to do on a clear night using a white star as a point source. It may also help if you intentionally under or overexpose the image to better see what the abberations are doing and where the optimal point of focus is. Once you do this, verify that wide open and f8 are also acceptable and you should be good to go.

06-24-2014, 03:06 AM	#12
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	Should I use close objects also?

06-24-2014, 07:18 AM	#13
jbondo Loyal Site Supportaxian Join Date: Sep 2013 Location: Texas Photos: Albums Posts: 503	No need to calibrate anything up close. The factory distance scale ring will be correct for shorter distances once infinity is calibrated.

06-24-2014, 05:15 PM	#14
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	Read long ago that infinity wasn't always the sharpest. I don't remember if this was the case just on one-touch zooms or it if included primes.

07-08-2014, 05:40 AM	#15
tabl10s Veteran Member Join Date: Jun 2011 Location: Sacramento(formerly from B'Ham, England). Posts: 1,424 Original Poster	Originally posted by stevebrot What are you calibrating? Aside from adjusting infinity focus (not always possible), there is nothing to calibrate on a manual focus lens. Now if you are talking about calibrating the PDAF system against one of your manual focus lenses, that is another matter. I am not sure what you have in mind, but it is my understanding that per lens assignment of custom calibration is not possible for lenses that don't support the data contact (are not chipped to provide unique identification to the body). That would include all manual focus lenses that I am aware of. Confirmation would be whether the camera prompts for focal length on start-up. Chipped lenses provide that information. Non-chipped lenses don't. It may be possible to assign a global setting and save that configuration as a custom user. In that case, you should do the calibration wide-open. Steve I just found this on the LensAlign site: Does LensAlign work for manual focus lenses? / LensAlign / Knowledge Base - Michael Tapes Design Support