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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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 Posted: Tue Nov 05, 2013 7:55 pm Post subject: Lens testing with a help of teleconverter |
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macheck wrote:
Having been inspired by Ray Parkhurst http://forum.mflenses.com/yet-another-pancolar-2-50-m42-star-wars-t62546.html, may I present the results of teleconverter as a "magnifying glass" when the one wants to do assess the sharpness of a lens and the sensor is not enough.
I do not know if this methodology is a common practice for you but it was not for me so allow me to share the results.
The subjects of testing were: Pancolar 2/50 (the one and only) , Helios-44M-4 2/58(selected one) and Pentacon MC 1.8/50 (random one). Teleconverter was M42 Beroflex 3X, camera Pentax K10D.
The testing scene, Pancolar 2/50 f5.6:
Pictures were taken: without teleconverter (TC) lens full opened, without TC lens stopped to f5.6 and with (TC) lens full opened.
Auto levels of IrfanView were applied, crops may, between each other, differ a little since were done manually.
Below are 100 % crops with no TC (max aperture and f5.6) and corresponding to 100%, picturec of 33% crops with TC.
Pancolar 2/50 f2 no TC, crop 100%:
Pancolar 2/50 f5.6 no TC, crop 100%:
Pancolar 2/50 f2 with TC, crop 33%:
Helios-44M-4 2/58 f2 no TC, crop 100%:
Helios-44M-4 2/58 f5.6 no TC, crop 100%:
Helios-44M-4 2/58 f2 with TC, crop 33%:
Pentacon MC 1.8/50 f1.8 no TC, crop 100%:
Pentacon MC 1.8/50 f5.6 no TC, crop 100%:
Pentacon MC 1.8/50 f1.8 with TC, crop 33%:
One can observe that the first two lenses are comparable the third being inferior.
To emphasize the differences, below the same as above but the 100% crops are now the pictures taken with TC (corresponding to 300% crops with TC that were done but are here not presented).
Pancolar 2/50 f2 with TC, crop 100%:
Helios-44M-4 2/58 f2 with TC, crop 100%:
Pentacon MC 1.8/50 f1.8 with TC, crop 100%:
Now the details are more visible and the inferiority of the third lens is more pronounced.
I am impressed that the Helios (even the chosen one) can be comparable (by the means of sharpness with Pancolar).
I have a feeling I could use 4x TC (but have one 2x and one 3x).
Comments remarks and other lens testing results are very welcome.
Machek
Last edited by macheck on Wed Nov 06, 2013 10:38 pm; edited 2 times in total |
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ForenSeil
Joined: 15 Apr 2011
Posts: 2726
Location: Kiel, Germany.
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| Posted: Tue Nov 05, 2013 8:09 pm Post subject: |
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ForenSeil wrote:
I would try an ~5x APO barlow lens or an very good APO TC instead of an normal TC or stacket TC, they have much better quality.
Most TC don't work well with short focal lengths, keep that in mind.
Another method would be to use decent high magnification eyepieces from micoscopes or telescopes instead of an TC+camera.
A cheaper and more precise but much more laborious method would be to use a high resolution film, an good analog body and an 4x-10x microscope lens or reversed enlarger lens for digitalisation. That's almost like Zeiss is testing the resolution of their modern lenses.
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I'm not a collector, I'm a tester 
My camera: Sony A7+Zeiss Sonnar 55/1.8
Current favourite lenses (I have many more):
A few macro-Tominons, Samyang 12/2.8, Noritsu 50.7/9.5, Rodagon 105/5.6 on bellows, Samyang 135/2, Nikon ED 180/2.8, Leitz Elmar-R 250/4, Celestron C8 2000mm F10
Most wanted: Samyang 24/1.4, Samyang 35/1.4, Nikon 200/2 ED
My Blog: http://picturechemistry.own-blog.com/
(German language) |
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poilu
Joined: 26 Aug 2007
Posts: 10471
Location: Greece
Expire: 2019-08-29
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| Posted: Tue Nov 05, 2013 9:06 pm Post subject: |
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poilu wrote:
| ForenSeil wrote: |
| A cheaper and more precise but much more laborious method would be to use a high resolution film, an good analog body and an 4x-10x microscope lens or reversed enlarger lens for digitalisation. That's almost like Zeiss is testing the resolution of their modern lenses. |
according to Zeiss, only a research microscope can do the job
| Zeiss wrote: |
| The resolution test chart was placed in the center of the frame, and the negatives were inspected directly on a research microscope. No other process involving projection (through even the best enlarging lens) or digitizing (in today’s best currently available scanners) is capable of transferring such high resolution values. |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Wed Nov 06, 2013 12:48 pm Post subject: |
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macheck wrote:
For the reference if anybody is interested.
The distance to yellow wall building is 820 m, the horizontal distance between tiles on its roof is about 0.2 m so it gives about 12 um on the sensor.
The distance to chimney is 11 km.
Distances measured in Google Earth.
ForenSeil wrote:
| Quote: |
| I would try an ~5x APO barlow lens or an very good APO TC instead of an normal TC or stacket TC, they have much better quality. |
It would be nice to have a piece of glass marked APO but for purpose of a quick and relatively simple observation, I think, normal TC will suffice.
Due to the simplicity and crude instruments used it is rather a comparatory method so pursuit for means of absolute readings is a different story.
ForenSeil wrote:
| Quote: |
| Most TC don't work well with short focal lengths, keep that in mind. |
I hope 50 mm is not a short one but I try with shorter focals.
Generally TC gives distortions of its own and magnifies distortions of the lens so as long as the center of picture is sharp then it is OK.
When taking a picture I am not an enthusiast of using TC's at all.
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Wed Nov 06, 2013 3:43 pm Post subject: |
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Ray Parkhurst wrote:
| poilu wrote: |
| according to Zeiss, only a research microscope can do the job |
This is of course marketing BS. This sort of testing is done all the time with simple optical benches. What matters is the quality of the objective, but the majority of Zeiss objectives are unusable outside a Zeiss optical system You won't see folks using them for photomacrography or even photomicrography since the objectives require correcting oculars to fix the (intentional) aberrations. Zeiss could make fully corrected objectives, but choose to make them such that they require matched oculars to fix the aberrations in the objectives. Keeps you from putting a Nikon or Olympus objective on a Zeiss platform.
Zeiss' research-grade optics are fully-corrected, so what they should have said is that "it requires a Zeiss research microscope, with fully corrected optics, to do the job." Any old run of the mill Oly or Nikon system can do just as well, and you don't even need a microscope, just an objective. |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Wed Nov 06, 2013 8:35 pm Post subject: |
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Ray Parkhurst wrote:
It looks like you have the Helios f2 with and without TC images swapped? |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Wed Nov 06, 2013 10:53 pm Post subject: |
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macheck wrote:
Ray Parkhurst wrote:
| Quote: |
| It looks like you have the Helios f2 with and without TC images swapped? |
But what makes you think so.
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Thu Nov 07, 2013 2:29 am Post subject: |
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Ray Parkhurst wrote:
| macheck wrote: |
It would be nice to have a piece of glass marked APO but for purpose of a quick and relatively simple observation, I think, normal TC will suffice.
Due to the simplicity and crude instruments used it is rather a comparatory method so pursuit for means of absolute readings is a different story. Macheck |
My favorite TC for this type of testing is the Vivitar 2x Macro Teleconverter. I have not found a 2x with better performance.
Of course if you're trying to quantitatively measure the lens performance, rather than just doing comparative testing, you need higher magnification. A good rule of thumb is to use enough magnification such that the image on sensor is 2 stops beyond the DLA of the sensor. This allows you to downsize the 100% crops by 2x to reduce the aberrations introduced by the sensor and AA filter. So for the f2 lens, on the K10, you'd use a 10x objective. A Nikon 10x/0.25 objective will give you enough resolution for quantitative tests if that's your thing, and can be purchased for <$100. |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Thu Nov 07, 2013 2:34 am Post subject: |
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Ray Parkhurst wrote:
| macheck wrote: |
Ray Parkhurst wrote:
| Quote: |
| It looks like you have the Helios f2 with and without TC images swapped? |
But what makes you think so.
Macheck |
The "without TC" image has more depth of field than the "with TC". This is optically incorrect, so it appears the images are swapped. |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Thu Nov 07, 2013 10:03 pm Post subject: |
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macheck wrote:
Ray here are:
Helios f2 no crop:
and Helios f2 with TC no crop :
So I think there is no swap.
What is the method of applying microscope lens ?
Where to attach it ?
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Fri Nov 08, 2013 2:41 am Post subject: |
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Ray Parkhurst wrote:
| macheck wrote: |
Ray here are:
Helios f2 no crop:
and Helios f2 with TC no crop :
So I think there is no swap.
What is the method of applying microscope lens ?
Where to attach it ?
Macheck |
OK, I suppose I was thrown off by the change in magnification or something. What this means is that the TC is magnifying the aberrations of the lens as the TC image is less sharp than the non-TC. Not expected, though I suppose it should have been. Apparently the Helios has some issues at f2.
To test the lens with an objective, you must first mount the objective to the camera with proper extension. Usually they require 160mm extension, and this is from sensor to end of the objective. The lens is mounted on a holder that supports the lens such that it points toward the test subject, chart, etc. Let's assume the subject is far away and that the lens is focused at infinity. The camera is then placed such that the objective is 1 focal length plus the objective working distance from the lens. The idea is to have the objective "observe" the virtual image formed by the lens at the sensor plane. The objective axis and lens axis should be coincident. |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Fri Nov 08, 2013 5:19 pm Post subject: |
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macheck wrote:
I did an ad hoc stand modifications, distances not adjusted, is it this method?
I found this Helios' at least center sharpness comparable to my Pancolar's when observing through TC (vide my first post).
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Fri Nov 08, 2013 8:35 pm Post subject: |
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Ray Parkhurst wrote:
| macheck wrote: |
I did an ad hoc stand modifications, distances not adjusted, is it this method?
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Looks good. What mag objective are you using? |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Sat Nov 09, 2013 11:35 pm Post subject: |
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macheck wrote:
I have 5x, 6.5x, 10x, 20x, did some microscope observations of lens with 10x objective and 15x eyepiece.
Recently I accuired Pancolar MC 1.8 50 worth testing and did 3x TC picture, different day different air.
Pancolar MC 1.8/50 f1.8 with 3xTC 100% crop:
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Sun Nov 10, 2013 2:05 am Post subject: |
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Ray Parkhurst wrote:
| macheck wrote: |
I have 5x, 6.5x, 10x, 20x, did some microscope observations of lens with 10x objective and 15x eyepiece.
Recently I accuired Pancolar MC 1.8 50 worth testing and did 3x TC picture, different day different air.
Pancolar MC 1.8/50 f1.8 with 3xTC 100% crop:
Macheck |
With the 3xTC you should be able to go to f3.3 before seeing any diffraction degradation on the image. I'm not sure what the f-stop ratios are for an f1.8 lens, but it would be nice to see an aperture sweep from f1.8 to f4, including f3.3 if possible, to see where this lens has its best sharpness. The 3xTC is giving you a very good test bed for checking sharpness and I expect you'll be able to discern the optimum aperture for this lens using it. |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Sun Nov 10, 2013 3:15 pm Post subject: |
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macheck wrote:
Ok I did it.
Pancolar MC 1.8 50, tripod, aperture stepping as the f-stop pin locks - f1.8, f1.8+1:(f2), 1.8+2:(f2+1), f2.8, f2.8+1 etc... up to f11.
Best to download all of them and view one by one.
1. f1.8
2. f1.8+1
3. f1.8+2
4. f2.8
5. f2.8+1
6. f4
7. f4+1
8. f5.6
9. f5.6+1
10. f8
11. f8+1
12. f11
I think the best is at f5.6
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Sun Nov 10, 2013 6:19 pm Post subject: |
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Ray Parkhurst wrote:
Nice aperture sweep! I agree that f5.6 seems to be the best aperture for this lens in the 3xTC system. The f4 image is also quite sharp, but the f4+1 is less sharp, which seems odd, then the f5.6 is slightly sharper than f4 but a lot sharper than f4+1. This method works best when the effective aperture at its optimum is at the DLA of the lens. You're not too far off, though your optimum is slightly beyond the DLA of the sensor so it's tough to tell if the sensor diffraction effects are limiting, or the lens, but I doubt you'd end up with more than 1/2 stop difference either way. One way to eliminate sensor limiting is to simply downsize the images by 2. This doubles the sensor DLA, and reduces the effects of the AA filter (if there is one). Here are your images downsized by 2x:
Downsized, I think the 5.6+1 is best...Ray |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Sun Nov 10, 2013 10:55 pm Post subject: |
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macheck wrote:
Thank you Ray, you have noticed that f4+1.
I think there was a micro motion blur or something similar, so have to repeat f4-f5.6 (it is so dark in those days), otherwise this lens has an oddity at f4+1  .
Macheck
Last edited by macheck on Mon Nov 11, 2013 1:31 pm; edited 1 time in total |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Mon Nov 11, 2013 1:29 pm Post subject: |
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macheck wrote:
The addendum: Pancolar MC 1.8/50 at f4, f4+1 and f5.6, there was no oddity just a micro-blur.
f4:
f4+1
f5.6:
Macheck |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Wed Nov 13, 2013 9:35 pm Post subject: |
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macheck wrote:
T aus Jena 2.8/50 M42 (CZJ Tessar):
f2.8
f2.8+1
f4
f4+1
f5.6
f5.6+1
f8
f8+1
f11
My observations (keeping in mind that it was done with 3xTC): relatively sharp at f2.8 to f4+1, DLA very pronounced starting at: f5.6.
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Thu Nov 14, 2013 1:35 pm Post subject: |
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Ray Parkhurst wrote:
f2.8+1 looks sharpest, though I think f4 suffers from microblurs since it seems less sharp than either f2.8+1 or f4+1. You can already see diffraction coming in at f4+1. |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Mon Nov 18, 2013 9:40 pm Post subject: |
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macheck wrote:
Thank You for the reply Ray, I hope others are interested too.
Comparing 2.8/50 Tessar to other tested lenses is the diffraction caused effect so visibly and quickly manifested (about f4-f5.6). I think other abberations played their role too.
Continuing - Helios 44m-4 2/58:
f2:
f2+1:
f2.8:
f2.8+1:
f4:
f4+1:
f5.6:
f5.6+1:
f8:
f8+1:
f11:
f16:
Sharpest at f2.8 to f4+1.
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Tue Nov 19, 2013 4:42 am Post subject: |
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Ray Parkhurst wrote:
Nice and sharp at f2.8+1...f4. I assume f2.8+1 is ~f3.3, which is f9.9 effective with 3xTC, right on the edge of your sensor's DLA, so is the sweet spot for this system... |
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macheck
Joined: 30 Oct 2013
Posts: 131
Location: Poland
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| Posted: Tue Nov 19, 2013 7:18 pm Post subject: |
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macheck wrote:
Nevertheless, Auto Revuenon 1.9/50 (Chinon):
f1.9:
f2.8:
f2.8+1:
f4:
f4+1:
f5.6:
f5.6+1:
f8:
f8+1:
f11:
f16:
"Best" at f8 to f8+1 !?
Macheck |
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Ray Parkhurst
Joined: 04 Jul 2011
Posts: 497
Location: Santa Clara, CA, USA
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| Posted: Wed Nov 20, 2013 3:04 am Post subject: |
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Ray Parkhurst wrote:
Disappointing for a f1.8 lens. Oddly, it looked worse at f2.8 than f1.8. |
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