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Forum: Pentax Medium Format 02-14-2012, 08:33 AM  
Which lens adapter for Mamiya 646 and Pentax 6x7 lens
Posted By popkrab
Replies: 2
Views: 1,923
Hello, I have a Mamiya 645 200 f2.8 apo and mamiya 645 150 f3.5N. I would like to use these lens with my Nikon D700 as well as Canon EOS 60D. Can anyone suggest me which lens adapter is good for my camera body and the lens?

I bought Fotodiox last 1-1.5 years ago (M645 to NikonF lens adapter pro grade). I don't like it much because between Mamiya lens and the adapter is not connect securely well in my opinion.

I also have a Pentax 6x7 300 f4 ed(if). I also would like to buy an adapter for my cameras too.

I'm looking for a good quality of a lens adapter. Please suggest where I can buy from.

Thank you very much.
Best Regards,
Pornchai POP
Forum: Pentax Medium Format 12-16-2011, 01:35 AM  
different between Pentax 6x7 300 F4 ED(IF) and 645 300 F4 ED(IF)
Posted By popkrab
Replies: 9
Views: 5,021
I don't have any medium format camera. I only have a Nikon D700. But I don't these medium format with my D700 camera. Actually, I will use for a Astronomical CCD camera to shoot star in the sky. I would like to take a shot in wide field. Wide field in astronomy should mean 300 mm. focal length or below.

The reason that I have to use a medium format lens because of the registered flange distance or back focus distance of these medium format lens are larger than in the 135 format lens like Canon or Nikon lens. Penatx 645 lens has a back focus distance around 70mm+/-, Pentax 67 lens has 84.95 mm. of back focus distance. These larger number allow me to an astronomical equipment such as camera filter wheel, focuser between CCD camera and the lens itself.

Astronomical CCD camera mostly are in black and white (monochrome). If I want in color shot, I have to shoot 4 set of color, red, green, blue and no filter (luminance). And then combine them together, after that, the photo will be in color.

I need high quality medium format lens because in the bright point light of subject like star, it usually introduce every aberration such as chromatic, spherical, coma and astigmatism. And I want to shoot wide open or just a little less of a f-stop due to the supper dim light of star. But if I shoot wide-open, it will introduce every aberration in the picture.

Not much medium format that can surpass this quality. I knew that Pentax 67 300 F4 ED(IF) is very good as well as Mamiya 645 200 F2.8 APO. If I use these two lens for a reference, can anyone recommend which lens should be good enough for wide-field astrophotography? I'm looking for a lens which have range of focal lenght around 100 - 300 mm.

1. First pic is a setup for what I described above.
2. 2nd pic is a sample of shot that taken using Mamiya 645 200 F2.8 APO
3. 3rd pic is the enlarge from very corner (red box) from the 2nd pic. Star shape at the corner of the frame should be
- sharp, rounded star shape
- no chromatic aberration. only show pure color of its star.
- no curvature of field. (center frame and corner frame should be same sharpness.
- no coma. no star trail radius from center frame to every corner of the frame.
- no astigmatism. (star must be rounded shape, not triangular, regular shape)

All photos is not mine, there are from Mr.Rolf Geissinger at his website: http://www.stern-fan.de/Seiten/frameset.htm

Thank you very much.
Best Regards,
Pornchai POP
Forum: Pentax Medium Format 12-15-2011, 03:52 PM  
different between Pentax 6x7 300 F4 ED(IF) and 645 300 F4 ED(IF)
Posted By popkrab
Replies: 9
Views: 5,021
Thank you very much Adam. I already read it. It is very useful based-on real use. I would like to hear information in comparing each-others

POP.
Forum: Pentax Medium Format 12-15-2011, 02:17 PM  
different between Pentax 6x7 300 F4 ED(IF) and 645 300 F4 ED(IF)
Posted By popkrab
Replies: 9
Views: 5,021
Hello group,

My name is Pornchai POP who is very new to this forum. I'm looking for an information about Pentax medium format lens. I'm looking for a 300 mm. medium format lens which I found a Pentax 645 300 F4 ED(IF) and also found Pentax 6x7 300 F4 ED(IF). The shape of the lens is very look similar as well as F4 ED(IF) too.

Is it different in the optical formula and sharpness, CA, other aberration? I saw many successful shot with 6x7 300 F4 ED(IF) but never see in a 645 version. The price of 645 version is much cheaper than in the 6x7 version even both are F4 ED(IF) designate.

Thank you very much.

Pornchai POP
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