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05-21-2017, 05:36 AM - 1 Like   #1
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Cosmicar/Pentax 8-48mm/f1.0-1.2 on the Q

This is a test of the Cosmicar/Pentax 8-48mm/f1.0-1.2 on the Q. I have compared the Cosmicar at 48mm with the Pentax 06 at 45mm.


The Cosmicar/Pentax has a solid metal body. It is certainly heavy compared with the 06! Being a c-mount TV lens, the aperture is stepless. But it handles well and focuses easily. It has a six blade aperture mechanism.


But on with the results. I photographed a callistemon flower in the garden. The main pics are cropped and resized at 20 per cent. All shots are jpeg SOOC to keep the playing field as level as possible:


Cosmicar/Pentax at 48mm f1.2 The image has quite a bit of glow and is predictably soft. However, I don't think is comes off too badly for f1.2 Note approaching bee.





Cosmicar/Pentax at 48mm f1.4 The image has quite a bit of glow and is still soft.





Cosmicar/Pentax at 48mm f2 The glow has mostly gone and the image is much sharper.





Now we are getting to the business end. Cosmicar/Pentax at 48mm f2.8 (left) and Pentax 06 at 45mm f2.8 (right). The 06 appears to have the edge. The Cosmicar has a tendency to blow out the highlights. Maybe this could be put down to the difference in coatings. Bokeh is fine, but six-sided in the Cosmicar pic if one looks closely.





Cosmicar/Pentax at 48mm f4 (left) and Pentax 06 at 45mm f4 (right). Another bee in the Cosmicar pic.






Cosmicar/Pentax at 48mm f5.6 (left) and Pentax 06 at 45mm f5.6 (right). Both images look good. The Pentax 06 may render a little cooler than the Cosmicar. The highlights are also better controlled with the Pentax 06.









Now the 100 per cent crops. First the Cosmicar, 48mm f5.6






... and the Pentax 06 45mm f5.6




The Cosmicar appears to have a slight edge in sharpness at this level. But it would be hard to beat the Pentax 06 with AF under most field conditions.


I got the Cosmicar/Pentax because I wanted a very fast lens to use under adverse lighting conditions (such as taking photographs in rainforest, where the light is very dim). It is early days yet, but I think the Cosmicar/Pentax is a winner. It only cost $100 posted. The fact that it says Cosmicar/Pentax on the lens is a bonus.


Comments welcome.

05-21-2017, 08:32 AM   #2
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It's surprising to learn that the Q can explore vistas of fast lens technology the K mount cannot even approach without becoming stupidly huge and expensive. What's the crop factor of a Q? Imagine making an f/1.0-1.2 zoom in the APS-C or - God forbid - full frame equivalent without running well into the five figures (if you could even MAKE a lens like that for K mount; maximum possible usable diameter is 46mm and I suspect you would run out of rear element diameter room before you got to the maximum zoom length).
05-21-2017, 02:34 PM   #3
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I played with a couple of Cosmicar lenses last year, I did look into the 8-48mm but as it was mostly for the Q-S1 I passed as while it will cover the Q sensor it isn't quite rated for the Q-S1 instead I ended up with a pair of C10ZAME-2 10.5-105mm F1:1.4 lenses for 30 sold as seen both work although it cost as much to make a control box to do the zoom / focus and Iris, also a C6Z1218 12.5-75mm F1:1.8 which is at least a bit more practical to use.

I was more looking for a longer range rather than fast speeds although speeds under F4 are useful the 10.5-105mm isn't a very practical proposition while the 12.5-75mm is considerably more sensible I did find both rank for purple fringing though, but am considering giving the 12.5-75 another try as in an unscientific test the other day it did seem at least as sharp as an Adaptall 01A and no worse than the Tamron for CA which in either case was dealt with fairly well by the default settings in Camera Raw which I had not tried last year.

For me in your images above the 06 wins every time but as you say the fast aperture is of use to you.
05-22-2017, 03:32 AM   #4
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QuoteOriginally posted by pathdoc Quote
if you could even MAKE a lens like that for K mount
Based on the lens I have, I estimate the front element would need to have a clear diameter of 225mm and if everything scaled up proportionately (using 5.6 cubed as a multiplier) you would be looking at 75 kg or about 165 pounds - maybe a little less depending on what could be shaved off the body metal. But definitely no plastic mount. Focus would be a bit heavy, I think, so you would have to add the weight of a motor drive (not SDM!) and a specially designed powered trolley to shift the whole rig around.


We shouldn't suggest things like this. You know they'll all want one,

05-22-2017, 04:42 AM   #5
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QuoteOriginally posted by ABBANDON Quote
it isn't quite rated for the Q-S1
The Cosmicar/Pentax is c-mount, so it covers the 16mm movie film frame which has a diagonal (minimum image circle) of 12.7mm. The 1/1.7" sensor has a diagonal of 9.5mm so it would cover it easily. C-mount lenses should cover everything up to 2/3" sensors. Apparently some even get close on a 1" sensor. The Schneider Kreuznach 12.5mm-75mm f1.8 (c-mount) may be an option for longer length. But I take my hat off to anyone who can make their own control box!
05-22-2017, 05:34 AM - 1 Like   #6
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The Cosmicar Lenses are for TV or more often CCTV use though just because they have a C-mount it does not necessarily follow that they were designed to cover the 16mm format and in fact there are quite a range of CCTV format sizes the 8-48mm is listed for 1/2" format whereas the 12.5-75mm is listed as for 2/3" format. The diagonal of 1/2" is 8mm and the diagonal of 2/3" is 11mm

Link to a page giving a comparison of the various format sizes.

Link to Pentax Machine Vision Lenses PDF from 2012

I had a pretty good look into these last year and concluded from my point of view that for me the 8-48mm was not worth it as while it would cover the sensor of the Q10 I have it is not really capable of covering the sensor of the latter cameras at least on paper.


It is a pretty simple control box as it is a motorized zoom you need a reversible power supply to do the focus motor and zoom motor the iris control is a bit trickier as it a video iris but it kind of works it was just by the time you put it in a small plastic project box and get decent switches and sockets for the two cables the bits added up to about 30 the same price I had paid for the lenses.

I'll try and post a few pics of the monster later.
05-22-2017, 06:57 AM   #7
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Would love to see this monster control box lens!
Thanks
barondla
05-22-2017, 02:55 PM   #8
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QuoteOriginally posted by ABBANDON Quote
just because they have a C-mount it does not necessarily follow that they were designed to cover the 16mm format
Thanks for that info. Just out of interest I will check the image circle when I get back home. My lens is totally manual though. There never was provision for a motor drive.

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