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Author Topic: PQ / PQS lens offset techniques - Hy6  (Read 3154 times)
KevinGSaunders
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« on: April 14, 2013, 09:11:33 AM »
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Hi All,

I recently got my Hy6 back from Germany to get the Mod2 update. There were some other issues and I am pleased with the results. I have heard about Eric and company doing specific lens offsets and wonder if there is a specific protocol to do so.

I have also been doing some testing and on my 350mm PQS lens, I was surprised to find the best images at F45. I had never considered sharpness at this extreme but the CA is so bad as one opens up I thought the lens was going to be unusable. Today I am going to test the full range on my 180 and 110 as well. I thought that diffraction would take over on the 350 but this did not appear to be the case.

Back to the original topic, I greatly appreciate any advice to get the lenses focusing perfectly.
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FredBGG
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« Reply #1 on: April 14, 2013, 09:20:35 AM »
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Hi All,

I recently got my Hy6 back from Germany to get the Mod2 update. There were some other issues and I am pleased with the results. I have heard about Eric and company doing specific lens offsets and wonder if there is a specific protocol to do so.

I have also been doing some testing and on my 350mm PQS lens, I was surprised to find the best images at F45. I had never considered sharpness at this extreme but the CA is so bad as one opens up I thought the lens was going to be unusable. Today I am going to test the full range on my 180 and 110 as well. I thought that diffraction would take over on the 350 but this did not appear to be the case.

Back to the original topic, I greatly appreciate any advice to get the lenses focusing perfectly.

The fact that you are getting the best result is at f45 leads me to beleive that it is a focus calibration issue.
Long lenses in general have little CA. It could be that the CA you are seeing is longditudinal CA as a result of focus being a bit off.
At f45 your getting more depth of field so you are getting a sharper image. There may also be a small focus shift that is bringing the focus closer at f45, but I doubt it.

Try doing some focus bracketing to see if you can get a shaper image on one of the focus stacking shots before without blending the focus stack.
« Last Edit: April 14, 2013, 09:23:38 AM by FredBGG » Logged
Neil Folberg
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« Reply #2 on: April 14, 2013, 02:15:29 PM »
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Hello,

I also got the mod2 upgrade at the same time as I fixed power supply issues. It's a different camera - works so much better after the repair and the modifications are lovely. The big one for me is the AF offset which adjusts itself automatically when changing AF lenses - and it is SO accurate. I have been photographing bees collecting nectar with the AF 180 + 1.4 x + extension tubes and was shocked to see how easy it is to use the nominal aperture of 2.8 and get crisp focus with the leaf aptus 12 - you can see every hair on the bees.

I don't mean to imply that the AF can track the bees with that extreme telephoto and macro, but I do use it to get a quick focus on a petal or stem and then follow the bees manually.

I spent a solid day in the studio using a bar code sticker to adjust the focus offset of each lens. the camera was tethered so I saw the results pretty quick. For each lens, I tried a series of close and mid-distance shots using the AF or focus confirmation and then used the results to determine the best focus offset for each lens. It did take a while and it was a pain, but you have to do it just once. I stuck a little sticker on each lens with the correct number, but as I said, for AF lenses it is set automatically.

This is one heck of a system, it is just a pleasure and so exquisitely precise. There are occasional hiccups on the electronics, which are annoying, but I shot hundreds of frames today.

You'll work through this, no problem, just a little time.

Neil
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KevinGSaunders
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« Reply #3 on: April 14, 2013, 04:00:48 PM »
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Thanks Fred for the advice.

Neil, I am going to follow your plan here as well. BTW I do find a significant difference with the Mod2. I only have the 80 mm AFD, and have a 40, 110, 180 and 150 mm lenses all manual focus. I think the camera is fabulous and am so glad I got it over the others. My Aptus II-12R is cool too as the rotating sensor makes life very good indeed.

I ran a focus stack and am downloading it now for the 350 and will report back with results.

Thanks again.
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KevinGSaunders
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« Reply #4 on: April 14, 2013, 04:07:18 PM »
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Ok. I ran a focus stack and did in fact find one frame that was tack sharp at F11. Now somehow I have to duplicate this and then get the focus indicators to line up at this point.
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KevinGSaunders
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« Reply #5 on: April 14, 2013, 04:32:14 PM »
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So here is the result:

350mm 5.6 PQS.

33 plus offset yields perfect focus.

The big surprise, I found out the mirror slap was shaking the camera enough to cause movement. When I locked the mirror up, no problems!

Does this surprise anyone out there with long lenses?
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Gigi
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« Reply #6 on: April 14, 2013, 09:22:21 PM »
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Mirror lockup is key for long lenses. No surprise there at all. With MLU, you can get amazing results - once stuck in a jungle shooting on a monopod with the three little feet for stability - about 4' high, and was able to shoot a 4-8 seconds, once the mirror was up.

The offset on telephotos is quite nice - I thought my 150 Telexenar was a soft lens, only to find it needed to be dialed in. Once that was done, it came back into sharpness.

However, I think there is focus shift in the 300, as long shots seem a bit different for offset than closer ones - but its not used so much and usually around f 16.
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Geoff
Neil Folberg
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« Reply #7 on: April 15, 2013, 12:47:18 AM »
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On good solid ground, and without a center column, I find I can usually do without mirror lock up. A higher shutter speed helps significantly. By the way, Capture1 version 7 finally added mirror lock up to tethered operation for the Hy6.

Neil
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dergiman
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« Reply #8 on: April 15, 2013, 01:38:36 AM »
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Please stop mentioning how great the AFi-12R is! My Sinar 75LV is jealous.  Tongue
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Philipp Derganz Photography
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KevinGSaunders
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« Reply #9 on: April 15, 2013, 05:27:55 AM »
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Thanks all. I apologize for causing pain with the Aptus 75, but we have to soldier on with this project.

At this point I have done three panoramas, one with the 350, one with the 180 2.8 and another on my Rollei X-Act2 view camera with a Schneider APO Digitar 180. I have attached screen grabs from Capture One 7 and it looks like the accuracy of the VC lens makes that the winner, even though I can't get quite the reach. This hotel was about a mile away.

There is also no lens profile in C1 for the 180 or the 350, and I don't need one for the APO Digitar 180 as it is so accurate.

If you have any perspectives, I would be most grateful. Thank you all for your kind assistance here too.
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Gigi
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« Reply #10 on: April 15, 2013, 11:34:39 AM »
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what ISO are you shooting at? The Leaf files will sharpen up v. nicely at ISO 50.
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Geoff
KevinGSaunders
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« Reply #11 on: April 15, 2013, 01:29:53 PM »
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These are all at ISO 50.
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jdabir
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« Reply #12 on: April 15, 2013, 08:41:20 PM »
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Thanks Fred for the advice.

Neil, I am going to follow your plan here as well. BTW I do find a significant difference with the Mod2. I only have the 80 mm AFD, and have a 40, 110, 180 and 150 mm lenses all manual focus. I think the camera is fabulous and am so glad I got it over the others. My Aptus II-12R is cool too as the rotating sensor makes life very good indeed.

I ran a focus stack and am downloading it now for the 350 and will report back with results.

Thanks again.

Hi there,

Is the Focus adjustment only for digital backs or is it also applicable for 6X6 film back?

Thanks,

Jim 
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KevinGSaunders
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« Reply #13 on: April 16, 2013, 09:23:51 AM »
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Jim, I think the focus adjustment is for the camera, which is independent of what is on the back. It should work for film as well but I cannot confirm.
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EricWHiss
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« Reply #14 on: April 16, 2013, 10:56:52 AM »
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This is correct.  It will work for both.   
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jdabir
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« Reply #15 on: April 18, 2013, 12:25:45 PM »
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Thank you.  I guess I am confused about its need.  My 6008i/6x6 and 6008AF/6X6 could not do this and photos were always super sharp.  Why would I need to adjust for hy6mod2?

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Gigi
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« Reply #16 on: April 18, 2013, 04:52:08 PM »
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In one sense, you don't. The tolerances for film are greater than they are for digital - and the offset allows for a micro-adjustment, to get the focusing exactly on the film/sensor plane. If you are happy with your film back and lenses without this, there is no reason to get into this. But there is another level of precision required for digital backs, and this kind of tuning is more necessary than one would at first think. Some years back, Joseph Holmes broke open this issue, as he shimmed an Alpa back and got a much higher level of sharpness with the back "dialed in" than he (or anyone else) expected.

The Rollei Hy6 is one of the first cameras to have this capability built in, although it is now available in a number of others. It also allows for some discrepancy between the film plane location (as designed) and the digital back plane (as provided by third party vendors) to be easily corrected.
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Geoff
KevinGSaunders
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« Reply #17 on: April 19, 2013, 11:16:06 AM »
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I purchased a Lens Align system and calibrated all the lenses at relatively short range. All needed it. I was surprised at how far off the lenses were. I need to repeat the testing at infinity or thereabouts to see if the settings are consistent throughout the range.
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Gigi
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« Reply #18 on: April 28, 2013, 01:24:41 PM »
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Attached here is a writeup on how to setup focus offset, as well as other information on the Hy6:

« Last Edit: April 29, 2013, 06:59:30 AM by Geoffreyg » Logged

Geoff
jdabir
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« Reply #19 on: April 28, 2013, 07:55:42 PM »
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Looks like there is an issue with the site.
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