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Pentax 100 SDUF II vs. SMC Pentax M-67 400mm ED

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#1 Mopman

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Posted 09 February 2013 - 06:58 PM

Assuming same price and availability, which is better for astrophotography ... and for daylight photography: Pentax 100 SDUF II refractor or the SMC Pentax M-67 400mm ED lens? Why :question: Let's not consider the adjustable f-stop. This would be with both medium format Pentax 67 film camera and a full frame DSLR. Thanks! :bow: Gary

#2 Nightfly

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Posted 09 February 2013 - 07:48 PM

Not owning or using such great lenses, I have heard the SDUF produced superior results. As you mention, for daylight photography you will be stuck at f/4 as there is no diaphragm. The SDUF has several attachments for various camera /visual uses. Both would require a knife edge focuser as the infinity stop on the SMC Pentax is adjustable. Both would make a fine optic. I like the adjustable aperture of the SMC if I were to take full advantage of it as a daytime optic. Even for astro, I would like the f/5.6 stop on occasion, especially if using it full frame on the 67.

Good luck.

#3 Hikari

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Posted 09 February 2013 - 11:24 PM

The telescope is most likely corrected for infinity whereas the telephoto is for a greater focusing range. How important that is, I am not sure. I know they share a similar design. And as Nightfly pointed out, you can stop down the lens--I am unsure why you want to ignore that. The lens will be easier to focus for daytime use. The lens cannot be used as a telescope.

#4 Nebhunter

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Posted 10 February 2013 - 01:27 AM

Hi Gary.

I tried using my 80mm apo scope with 35mm camera for daytime photography. Walking around in the 5 acre woodlot near home I managed to sneak up on a nice redtail hawk sitting on a branch. The outfit was already attached to a sturdy wooden tripod, but by the time I got it opened up - and found the hawk in the view finder - out of focus of course - and cranking the 2 speed focuser to get close - never mind fine focus - the hawk was long gone.

It was fine for something where you had lots of time to set up and dial everything in - sort of like using a LF camera. So I gave up on the idea with the scope.

I have the 400 EFif lens - and have shot it hand held on flying Osprey - even with the 1.4x converter turning it into a 560mm lens at f/5.6. Having converters gives more flexibility to the lens. Shooting from a tripod - yes focus is fast and you can pivot around to find a subject and quickly get set to capture it. Having DOF control will give you more options for landscape.

Last item is filters. The lens has a rear filter holder for 67mm filters. There is a top "drawer" that is quickly removed to which you thread the filter. Slide it back in, lock the knob - done. Great if you want to shoot B&W film.
It's a honking big lens - and I love it.

I have found one issue however that has caused some not so sharp astro images - but has nothing to do with the lens. The Pentax 67 - both my astro cameras have this issue. The film door when closed is not fully tight or latched properly due to age and wear and tear on the latches plus gaskets. I found this by squeezing the door and found it could be moved in tighter. Let go and the door would give.

I set up a poster on a wall and levelled and squared the camera with the 200 SMC lens at f/4 as close as the lens would focus. Took some B&W shots with the door in it's looser closed position - and then with a large paper clamp squeezing the door closed tight. The difference was easily seen on the film and when scanned.

No clamp - focus was very good from the middle to the hinge end - but fuzzy towards the latching end with small print very difficult to read.

Clamped shot - sharp from corner to corner with print easily readable. Now I use this paper clamp on both cameras for astro or landscape. Yes - I now have to re-shoot everything - as I know it will be way better. Which is fine by me.

Igor

#5 Nightfly

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Posted 10 February 2013 - 09:38 AM

I mispoke about not having used the SMC 400. I had a brief affair with one. An affair from which I have never fully recovered.

Posted Image

Thanks Igor.

#6 Mopman

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Posted 10 February 2013 - 01:30 PM

Thanks guys!!! Totally hypothetical ... I don't have a line on either (or could afford for that matter) I was just curious about the difference in optics. BTW: I posted the same question in the Refractor forum and hand no response. Both the scope and the lens look fantastic cosmetically. Thanks Igor for the tip on clamping the film door; I will have to check that out! Thanks again :bow: Gary

#7 Nebhunter

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Posted 10 February 2013 - 11:40 PM

We definitely need to try that one again Jim. If all works out well on my end and I get the power of old age security working for me - maybe this fall?

igor

#8 Nightfly

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Posted 12 February 2013 - 06:23 AM

Looking forward to it Igor. There is time to plan. Don't forget the 400 :D

#9 Michal1

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Posted 12 February 2013 - 04:51 PM

Hi Mopman! I've heard some of the DSLR users complained to a certain amout of chromatic abberation of SDUF II. You can see a lot of examples of photos taken using SMC 400 at Nebhunter's gallery and at estellar.de .






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