TL;DR: With the Epson flatbed, all tested apertures of this lens, with and without the teleconverter, resolve the same at 28 line pairs per mm. About enough to make a 10 inch print at 35mm. With the Pentax K-1 and pixel shift, the lens without teleconverter at f/5.6 outresolves the camera and test target at greater than 44 line pairs per mm. Nearing 20 inch print at 35mm and 30 inch for medium format. Using the teleconverter at f/5.6 is about the same resolution as using the lens by itself wide open at f/2.8: both very sharp and approaching the resolution limits of my DSLR digitization rig. A person can use this lens and teleconverter together for a 380mm f/5.6 lens which is quite good for the price, either on 35mm or medium format.
Disclaimer: I am someone who enjoys photography, not a professional photographic scientist, to whom some of my methodology would make cringe. However, these findings are good enough to be illuminating to me and others interested in the performance of the Pentacon Six Carl Zeiss Jena Sonnar 180mm f/2.8 and the Arsat 2X K-6B Teleconverter. There wasn't much to look at on the internet in terms of tests of this so I made my own.
Canon EOS Elan 7E. Evaluative metering with +2 stops exposure compensation, tripod, MLU, 10 second timer. Pentacon Six to EOS glassless adapter. Test target shot near minimum focus distance of 1.7 meters without teleconverter, and roughly double that with teleconverter.
Frame Aperture Shutter Speed
22 TC f/2.8 1/30
23 TC f/4 1/15
24 TC f/5.6 1/8
25 TC f/8 1/4
26 f/2.8 1/125
27 f/4 1/60
28 f/5.6 1/30
29 f/8 1/15
5% added to all LP/MM values due to negatives including 5% extra outside of test chart. Limitation of viewfinder.
Kodak Vision 250D film used @400. Cinestill C-41 kit, developer 5 minutes 37C, blix 8 minutes.
Note that "True Megapixel" values will seem low because digital cameras don't really resolve true detail between every pixel. In other words you can't shoot 3000 white and 3000 black lines on a digital camera that has 6000 pixels on the long side and be able to tell the lines apart. The megapixel counts of digital cameras are very inflated as far as resolution goes. You need about 3 true megapixels to make a good 9x6 print and about 8 true megapixels to make a good 15x10 print for the purpose of this analysis. Don't try to compare it to the rated pixel counts of digital cameras.
Note that LP/MM values are the limits using my particular setup, not necessarily the upper limit of the lens itself.
No digital sharpening was applied at any point in these comparisons. You could possibly improve these numbers by adding some, but I just don't like the look of digital sharpening.
These results are from the center of the frame, but in my previous testing the Sonnar maintains great resolution right to the edge of a 6x6 frame. The teleconverter only drops in resolution on the extreme edge of a 6x6, the part you might accidentally crop off, so it's pretty good too.
Crops shown are the center 4 megapixels of 36-megapixel full frame images. You need to view them at 200% to observe the line pairs. Link to large test image.
Epson 4490 @2400dpi (increasing beyond this dpi does not really improve resolution) results:
True for all apertures with and without teleconverter.
Adjusted LP/MM: 28
True Megapixels (36x24mm): 2.7
True Megapixels (56x41mm): 7.2
True Megapixels (56x56mm): 9.8
Epson results not shown in image as they are all too similar to be interesting.
Pentax K-1 50mm f/2.8 macro pixel shift digitization results:
f/2.8
No Teleconverter
Horizontal Lines Per Picture Height: 18.5
Vertical Lines Per Picture Height: 19.5
Horizontal Adjusted LP/MM: 40
Vertical Adjusted LP/MM: 43
True Megapixels (36x24mm): 5.9
True Megapixels (56x41mm, stitched frames): 16
True Megapixels (56x56mm, stitched frames): 22
With Teleconverter
Horizontal Lines Per Picture Height: 12.5
Vertical Lines Per Picture Height: 14.5
Horizontal Adjusted LP/MM: 27
Vertical Adjusted LP/MM: 32
True Megapixels (36x24mm): 3
True Megapixels (56x41mm, stitched frames): 8
True Megapixels (56x56mm, stitched frames): 11
Notes: Teleconverter images perfectly usable wide open, if intent on 35mm is prints 10 inches or smaller, or intent on 56mm is prints 16 inches or smaller. For teleconverter, wide open result is same resolution on Epson vs. DSLR digitization and no advantage is gained. Without teleconverter, significant resolution is gained from DSLR digitization.
f/4
No Teleconverter
Horizontal Lines Per Picture Height: 19.5
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 43
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 6.5
True Megapixels (56x41mm, stitched frames): 17
True Megapixels (56x56mm, stitched frames): 24
With Teleconverter
Horizontal Lines Per Picture Height: 14.5
Vertical Lines Per Picture Height: 17.5
Horizontal Adjusted LP/MM: 32
Vertical Adjusted LP/MM: 38
True Megapixels (36x24mm): 4.2
True Megapixels (56x41mm, stitched frames): 11
True Megapixels (56x56mm, stitched frames): 15
Notes: Not much difference between f/2.8 and f/4 when no teleconverter is used. Moderate difference when teleconverter used.
f/5.6
No Teleconverter
Horizontal Lines Per Picture Height: Over 20
Vertical Lines Per Picture Height: Over 20
Horizontal Adjusted LP/MM: Over 44
Vertical Adjusted LP/MM: Over 44
True Megapixels (36x24mm): Over 6.7
True Megapixels (56x41mm, stitched frames): Over 18
True Megapixels (56x56mm, stitched frames): Over 24
With Teleconverter
Horizontal Lines Per Picture Height: 17
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 37
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 5.6
True Megapixels (56x41mm, stitched frames): 15
True Megapixels (56x56mm, stitched frames): 20
Notes: Highest number of fine lines resolved at f/5.6 with no teleconverter. Beyond the ability of my Pentax K-1 with 50mm macro lens at f/10 and pixel shift to pick up. At f/5.6 with teleconverter, it's about as sharp as f/2.8 without teleconverter.
f/8
No Teleconverter
Horizontal Lines Per Picture Height: 17
Vertical Lines Per Picture Height: 20+
Horizontal Adjusted LP/MM: 37
Vertical Adjusted LP/MM: Over 44
True Megapixels (36x24mm): Over 5.6
True Megapixels (56x41mm, stitched frames): Over 15
True Megapixels (56x56mm, stitched frames): Over 20
With Teleconverter
Horizontal Lines Per Picture Height: 14.5
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 32
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 4.9
True Megapixels (56x41mm, stitched frames): 13
True Megapixels (56x56mm, stitched frames): 18
Notes: Even though f/8 has slightly less resolution than f/5.6, it appears to make the sharpest image to the human eye, probably from an increase in microcontrast from reduction in ghosting and flaring. Only on this aperture can I clearly see the fine texture of the paper in the black areas on the test target.
Conclusion: f/8 makes the image which appears to be most detailed, while f/5.6 contains the highest actual resolution. Wide open is perfectly usable for moderately sized prints. The lens is a little better at resolving vertical lines than horizontal ones. The teleconverter is not a huge disadvantage in resolution for such a good lens. The main disadvantage of the teleconverter is losing 3 stops of shutter speed while handholding. The Pentacon Six 180mm Sonnar is an excellent lens that is sharp enough to use with or without a teleconverter even on 35mm format, and is superb on medium format. If you can manage its weight and slow focusing, it's a more affordable alternative to buying a 200mm f/2.8 35mm lens, or 400mm f/5.6 lens. And it's famous for having smooth and artistic out of focus areas and rendering.
Disclaimer: I am someone who enjoys photography, not a professional photographic scientist, to whom some of my methodology would make cringe. However, these findings are good enough to be illuminating to me and others interested in the performance of the Pentacon Six Carl Zeiss Jena Sonnar 180mm f/2.8 and the Arsat 2X K-6B Teleconverter. There wasn't much to look at on the internet in terms of tests of this so I made my own.
Canon EOS Elan 7E. Evaluative metering with +2 stops exposure compensation, tripod, MLU, 10 second timer. Pentacon Six to EOS glassless adapter. Test target shot near minimum focus distance of 1.7 meters without teleconverter, and roughly double that with teleconverter.
Frame Aperture Shutter Speed
22 TC f/2.8 1/30
23 TC f/4 1/15
24 TC f/5.6 1/8
25 TC f/8 1/4
26 f/2.8 1/125
27 f/4 1/60
28 f/5.6 1/30
29 f/8 1/15
5% added to all LP/MM values due to negatives including 5% extra outside of test chart. Limitation of viewfinder.
Kodak Vision 250D film used @400. Cinestill C-41 kit, developer 5 minutes 37C, blix 8 minutes.
Note that "True Megapixel" values will seem low because digital cameras don't really resolve true detail between every pixel. In other words you can't shoot 3000 white and 3000 black lines on a digital camera that has 6000 pixels on the long side and be able to tell the lines apart. The megapixel counts of digital cameras are very inflated as far as resolution goes. You need about 3 true megapixels to make a good 9x6 print and about 8 true megapixels to make a good 15x10 print for the purpose of this analysis. Don't try to compare it to the rated pixel counts of digital cameras.
Note that LP/MM values are the limits using my particular setup, not necessarily the upper limit of the lens itself.
No digital sharpening was applied at any point in these comparisons. You could possibly improve these numbers by adding some, but I just don't like the look of digital sharpening.
These results are from the center of the frame, but in my previous testing the Sonnar maintains great resolution right to the edge of a 6x6 frame. The teleconverter only drops in resolution on the extreme edge of a 6x6, the part you might accidentally crop off, so it's pretty good too.
Crops shown are the center 4 megapixels of 36-megapixel full frame images. You need to view them at 200% to observe the line pairs. Link to large test image.
Epson 4490 @2400dpi (increasing beyond this dpi does not really improve resolution) results:
True for all apertures with and without teleconverter.
Adjusted LP/MM: 28
True Megapixels (36x24mm): 2.7
True Megapixels (56x41mm): 7.2
True Megapixels (56x56mm): 9.8
Epson results not shown in image as they are all too similar to be interesting.
Pentax K-1 50mm f/2.8 macro pixel shift digitization results:
f/2.8
No Teleconverter
Horizontal Lines Per Picture Height: 18.5
Vertical Lines Per Picture Height: 19.5
Horizontal Adjusted LP/MM: 40
Vertical Adjusted LP/MM: 43
True Megapixels (36x24mm): 5.9
True Megapixels (56x41mm, stitched frames): 16
True Megapixels (56x56mm, stitched frames): 22
With Teleconverter
Horizontal Lines Per Picture Height: 12.5
Vertical Lines Per Picture Height: 14.5
Horizontal Adjusted LP/MM: 27
Vertical Adjusted LP/MM: 32
True Megapixels (36x24mm): 3
True Megapixels (56x41mm, stitched frames): 8
True Megapixels (56x56mm, stitched frames): 11
Notes: Teleconverter images perfectly usable wide open, if intent on 35mm is prints 10 inches or smaller, or intent on 56mm is prints 16 inches or smaller. For teleconverter, wide open result is same resolution on Epson vs. DSLR digitization and no advantage is gained. Without teleconverter, significant resolution is gained from DSLR digitization.
f/4
No Teleconverter
Horizontal Lines Per Picture Height: 19.5
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 43
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 6.5
True Megapixels (56x41mm, stitched frames): 17
True Megapixels (56x56mm, stitched frames): 24
With Teleconverter
Horizontal Lines Per Picture Height: 14.5
Vertical Lines Per Picture Height: 17.5
Horizontal Adjusted LP/MM: 32
Vertical Adjusted LP/MM: 38
True Megapixels (36x24mm): 4.2
True Megapixels (56x41mm, stitched frames): 11
True Megapixels (56x56mm, stitched frames): 15
Notes: Not much difference between f/2.8 and f/4 when no teleconverter is used. Moderate difference when teleconverter used.
f/5.6
No Teleconverter
Horizontal Lines Per Picture Height: Over 20
Vertical Lines Per Picture Height: Over 20
Horizontal Adjusted LP/MM: Over 44
Vertical Adjusted LP/MM: Over 44
True Megapixels (36x24mm): Over 6.7
True Megapixels (56x41mm, stitched frames): Over 18
True Megapixels (56x56mm, stitched frames): Over 24
With Teleconverter
Horizontal Lines Per Picture Height: 17
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 37
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 5.6
True Megapixels (56x41mm, stitched frames): 15
True Megapixels (56x56mm, stitched frames): 20
Notes: Highest number of fine lines resolved at f/5.6 with no teleconverter. Beyond the ability of my Pentax K-1 with 50mm macro lens at f/10 and pixel shift to pick up. At f/5.6 with teleconverter, it's about as sharp as f/2.8 without teleconverter.
f/8
No Teleconverter
Horizontal Lines Per Picture Height: 17
Vertical Lines Per Picture Height: 20+
Horizontal Adjusted LP/MM: 37
Vertical Adjusted LP/MM: Over 44
True Megapixels (36x24mm): Over 5.6
True Megapixels (56x41mm, stitched frames): Over 15
True Megapixels (56x56mm, stitched frames): Over 20
With Teleconverter
Horizontal Lines Per Picture Height: 14.5
Vertical Lines Per Picture Height: 20
Horizontal Adjusted LP/MM: 32
Vertical Adjusted LP/MM: 44
True Megapixels (36x24mm): 4.9
True Megapixels (56x41mm, stitched frames): 13
True Megapixels (56x56mm, stitched frames): 18
Notes: Even though f/8 has slightly less resolution than f/5.6, it appears to make the sharpest image to the human eye, probably from an increase in microcontrast from reduction in ghosting and flaring. Only on this aperture can I clearly see the fine texture of the paper in the black areas on the test target.
Conclusion: f/8 makes the image which appears to be most detailed, while f/5.6 contains the highest actual resolution. Wide open is perfectly usable for moderately sized prints. The lens is a little better at resolving vertical lines than horizontal ones. The teleconverter is not a huge disadvantage in resolution for such a good lens. The main disadvantage of the teleconverter is losing 3 stops of shutter speed while handholding. The Pentacon Six 180mm Sonnar is an excellent lens that is sharp enough to use with or without a teleconverter even on 35mm format, and is superb on medium format. If you can manage its weight and slow focusing, it's a more affordable alternative to buying a 200mm f/2.8 35mm lens, or 400mm f/5.6 lens. And it's famous for having smooth and artistic out of focus areas and rendering.
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