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Resolution target: a basic question

 
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austrokiwi1



Joined: 14 Sep 2014
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PostPosted: Fri Aug 14, 2015 11:10 am    Post subject: Resolution target: a basic question Reply with quote

I have a standard 1951 USAF resolution target. I want to compare some lenses so started to take some photos of the target... and here came my problem. My eye sight even with the cameras focus magnification assist on can not get the focus accurate enough to even try to resolve group 7. ( I use a cut down Olympus CH2 microscope as a subject stage). I know the 105mm Printing nikkor should be up to the task. so what do I do to actually get an accurate in focus shot of the target?

I have a stackshot so would running a stack with 0.002mm steps be the easiest method to get an infocus shot?

The vertical rig is leveled and is vibration resistant( 29kg granite slab sitting on Sorbothane feet) and the table legs sit on 15 kg concrete pavers
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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rjlittlefield
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PostPosted: Fri Aug 14, 2015 11:33 am    Post subject: Re: Resolution target: a basic question Reply with quote

austrokiwi1 wrote:
I have a stackshot so would running a stack with 0.002mm steps be the easiest method to get an infocus shot?
Yes.

By shooting a short stack with very shallow steps, you will definitely get a shot that is arbitrarily close to best focus. Perhaps more important, by seeing the falloff on either side of best focus, you can be sure that you really do have the best one.

Focusing with magnified Live View to a large monitor can also help you to get good focus, but without the stack you'll always be left with some doubt about whether it could have been better.

--Rik
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austrokiwi1



Joined: 14 Sep 2014
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PostPosted: Fri Aug 14, 2015 11:50 am    Post subject: Reply with quote

Thanks
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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rjlittlefield
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PostPosted: Fri Aug 14, 2015 12:14 pm    Post subject: Reply with quote

One more thing... Be sure to set the StackShot controller into High Precision mode. See HERE for the explanation why. This is not so important if you're using the StackShot controller and motor to control the cut-down CH2 by running its fine focus. But if you're using the StackShot rail to do the movements, then High Precision is critical because without it, you'll will periodically get steps that are much larger than average.

--Rik
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austrokiwi1



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PostPosted: Fri Aug 14, 2015 12:40 pm    Post subject: Reply with quote

I had finished a stack and found in the series of photos some very large changes in focus....now i understand why.
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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rjlittlefield
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PostPosted: Fri Aug 14, 2015 5:44 pm    Post subject: Re: Resolution target: a basic question Reply with quote

One other issue...

austrokiwi1 wrote:
... can not get the focus accurate enough to even try to resolve group 7. ... I know the 105mm Printing nikkor should be up to the task.

You don't mention what camera you're using, or what magnification you're working at.

However, I assume because of the Printing Nikkor that you're operating around 1:1.

In that case, be aware that Group 7 may well be exceeding the resolution of your camera's sensor, even though it's trivially within reach of the Printing Nikkor.

See HERE for an example of the problem. That test was done with a Nikon D800E, 36 megapixels in full frame. That camera has pixels of size 36/7360 = 0.00489 mm, which permits at most 102 line pairs per mm of real resolution, even at the Nyquist limit of 2 pixels per line pair. But USAF 1951 Group 7 Element 1 is already 128 line pairs per mm, 20% above the cutoff frequency for the sensor. If that pattern were to resolve at all, it would be a matter of spurious resolution.

So, what camera are you using, and what magnification are you working at?

--Rik
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austrokiwi1



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PostPosted: Fri Aug 14, 2015 8:49 pm    Post subject: Reply with quote

(You missed my signature )Camera is Sony A7rII so 42MP with out a low bypass filter. EFCS is on, the fully electronic option is effectively a video scan and apparently introduces more noise so I don't use it. The shutter is also buffered against vibration and is rated for 500,000 actuation's. Am using the nikkor at 1X ( and the resolution target is a 1X target.


The Camera is a considerable improvement over the earlier version but it is only slightly better than the D810 for resolution(and just slightly behind the D810 in dynamic range).

The reason I am doing it, other than fun, is I want to get a real feel for how good the Sony 90mm F 2.8 macro G lens is. It is reported as being made for high resolution sensors. But there is a lot of hype about the lens at the moment and I want to sort fact from enthusiasm.. I tried it with the micro printing on a 10 Euro note and it appeared to be only slightly softer than the nikkor ( @1-1 and F/2.8 ) A quick try yesterday with the 90mm only managed 6 group 1 and that was "only just"

Last night the best shot was only resolving group 6 element 2 ( with the nikkor) I haven't tried high precision yet. Later today I will try again... and I have just realized I had forgotten to turn off IBIS. When I swap from a native lens I have to check the status of IBIS; either I am doing something wrong or the camera turns it back on. That might account for the lower than expected resolution I was hoping for 7 group 1 but that may be too much?.

the target is a 3 X3 positive from Edmunds... as it was an Ebay find first thing I did was throw a 10X objective on the bellows, using the camera to view. I was able to see that all of Group 7 is there and in good condition!!! with the 10 X objective all of group 7 was sharp( with IBIS on!!).
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8


Last edited by austrokiwi1 on Fri Aug 14, 2015 9:36 pm; edited 1 time in total
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rjlittlefield
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PostPosted: Fri Aug 14, 2015 9:33 pm    Post subject: Reply with quote

austrokiwi1 wrote:
(You missed my signature )

True enough. Signatures are not shown in the "Topic review" panel that appears while composing a message, so if information is contained only in a signature, I'm liable to miss it.

In addition to the 42 MP, I read that the A7rII does not have a low-pass filter. In theory, that makes it similar to the D800E and D810 except for resolution that is about 8% higher on each axis (sqrt(42/36) = 1.080). The steps between elements in the USAF chart are about 12%, so based on specs I would anticipate less than one group more detail than the D800.

I'm thinking a solid Group 6 Element 4, probably Element 5 with very low contrast, but yes, Group 7 Element 1 is out of reach. The Nyquist limit for 7952 pixels in 36 mm is only 110 lp/mm, not quite enough to reach even Group 6 Element 6 at 114 lp/mm. If the little block of bars happens to line up fortuitously with pixels it may appear to resolve, but that's just luck of the draw in where it hits the sensor.

--Rik
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austrokiwi1



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PostPosted: Fri Aug 14, 2015 9:42 pm    Post subject: Reply with quote

Thank you good to know that info ( I was editing my post while you entered yours so that is why your post now seems to include redundant info) from what you have said group 6 element 1 with the Sony 90mm is reasonably impressive. The sony ( camera) also has a back illuminated sensor. Would the greater light gathering ( less than a full stop I believe) make any difference, from what you have said I would anticipate a "no"
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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rjlittlefield
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PostPosted: Fri Aug 14, 2015 10:52 pm    Post subject: Reply with quote

austrokiwi1 wrote:
Would the greater light gathering ( less than a full stop I believe) make any difference, from what you have said I would anticipate a "no"

Correct. For high contrast detail, resolution is determined by the pixel size. The effective resolution for low contrast detail may be determined by noise, which is related to light gathering capacity, but that should not be an issue in this case.

Quote:
from what you have said group 6 element 1 with the Sony 90mm is reasonably impressive.

I would expect more. My experience with this sort of test -- high contrast target, central resolution only -- is that any decent lens should outresolve the sensor by several elements. Remember that HERE I demonstrated that an EL Nikkor 50 mm f/2.8 set on f/5.6 (f/11 effective) clearly resolved Group 7 Element 1 in the optical image, even though the D800E could capture only Group 6 Element 3. The 50 mm f/2.8 Schneider-Kreuznach Componon S, also not an expensive lens, was resolving Group 7 Element 4, maybe 5, in the optical image.

When testing your 90 mm, be sure to play around with the aperture setting. The highest ultimate resolution is likely to occur at wider apertures, even though overall contrast may be higher at narrow apertures.

--Rik
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austrokiwi1



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PostPosted: Sat Aug 15, 2015 12:53 am    Post subject: Reply with quote

Appreciate the advice. I will try again tonight. I just had another go. I manged to get group 6 element 4 resolved but then I realized yet again IBIS was on. So I deleted the series of shots re did it with IBIS off and bizarrely none of group 6 was in focus. Group five also looked pretty sick. Given that IBIS was set to the last manual focus lens I had on the camera( a zoom and I set IBIS to 70mm) I am a little puzzled ( only 3 axis stabilization was working). I am travelling tomorrow so if You don't see any more on this thread you will understand I have left this project till my return in 2 weeks.

I suspect my rig has some issues that need ironing out. I now have a geared column that has a locking screw but to assist with leveling issues I have two panorama Arca clamps which mounted vertically instead of Horizontally may be causing some problems
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Still learning,
Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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austrokiwi1



Joined: 14 Sep 2014
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PostPosted: Mon Aug 31, 2015 4:21 am    Post subject: Reply with quote

Got back from Holidays and had another go with the Sony Fe 90mm MAcro, @ 5.6 Group 6 element four is easily seen. I am still to try out various apertures. From what Rik has said as far as checking the resolution ability of the lenses I am not going to get very far simply because I am at the limits of the sensors resolution. For me whats more important is showing my rig is will allow me to get the best out of the camera and objectives. Now its just down to my old eyes
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Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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