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12-10-2014, 01:07 AM   #1
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Digiscoping PF-CA35 vs T adapter

Hello all my fellow Pentaxians,


I haven't posted before, but I've been following the forums for about a year.
I have finally decided that I cannot rely on holding my camera up to the eyepiece of my Pentax 65edII inline spotting scope and expect decent pictures. Heck half the time I don't get a picture at all because I am either rushing the shot or getting frustrated and merely zooming out then zooming in on the picture. I am an amateur rookie in the photo department. camera kit is K50 with the 18-135 / 18-55 / 55-300mm lens.
So I guess my real question is does anyone have a review or comparison between the Pentax PF-CA35 vs anyone of the T adapter's out there. Is there any advantages to the CA35? I will be using the digi-scoping both in the daylight while hiking/hunting as well as the great northern lights/celestial show's we get in the Yukon.
Any help or guidance would be much appreciated.

12-10-2014, 11:33 AM   #2
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QuoteOriginally posted by Ohmic Quote
Hello all my fellow Pentaxians,


I haven't posted before, but I've been following the forums for about a year.
I have finally decided that I cannot rely on holding my camera up to the eyepiece of my Pentax 65edII inline spotting scope and expect decent pictures. Heck half the time I don't get a picture at all because I am either rushing the shot or getting frustrated and merely zooming out then zooming in on the picture. I am an amateur rookie in the photo department. camera kit is K50 with the 18-135 / 18-55 / 55-300mm lens.
So I guess my real question is does anyone have a review or comparison between the Pentax PF-CA35 vs anyone of the T adapter's out there. Is there any advantages to the CA35? I will be using the digi-scoping both in the daylight while hiking/hunting as well as the great northern lights/celestial show's we get in the Yukon.
Any help or guidance would be much appreciated.
I've got the PF-CA35 and the PF-80EDA. When used on a tripod it gives photos that are suitable to identify the species of bird and therefore adequately document the bird, but too soft for publication purposes. That softness really shows up when you crop the photo.

I think I remember reading somewhere that when using a glass-less T adapter, the image from Pentax spotting scopes would fall too far in front of or too far behind the camera sensor for the focus wheel on the spotting scope to bring the image into focus.

The other major difference between the PF-CA35 and a hollow T adapter is that the optics in the former also serve as a 2X tele-converter, at least according to a user on this forum who is a physicist of optics and whose user name is "Falco". A Pentax brochure from 2005 says that with the PF-80ED that gives you a focal length of 1000mm and a fixed aperture of f12.5. Too long to hand hold steadily or to achieve focus easily because of the shallow depth of field at that focal length. A hollow T adapter would therefore give you a focal length of 500mm with the PF-80ED. The brochure also gives the focal length when using the PF-100ED, but not for the PF-65ED (no explanation in the brochure why this model is skipped).
12-11-2014, 01:39 AM   #3
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Wow, thanks for the info Pete-tarmigan. I have been researching a little on the forums here. There does seem to be a preference to PF-CA35. But I have seen some extendable hollow t mounts that may help with the sensor to scope focus spacing. We lost our local camera shop last year to retirement and its been very difficult to actually get my hands on lens adapter's to see first hand. As well he was a great resource for the very things your discussing. I am not sure by what you mean when you say its too "soft". Are you talking focus or sharpness.


Is there any chance you could post a picture of a bird you have shot with the PF-ca35. I checked the Ricoh website it does say that the PF-65edII is compatible with the adapter.


cheers
12-11-2014, 07:49 AM   #4
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QuoteOriginally posted by Ohmic Quote
Is there any chance you could post a picture of a bird you have shot with the PF-ca35. I checked the Ricoh website it does say that the PF-65edII is compatible with the adapter.

cheers
Here is a photo with the K-5, PF-CA35 and PF-80ED. The rig was mounted on a tripod and the shutter triggered with the Pentax Remote Control F. The file properties as shown in Microsoft Windows Explorer are: shutter speed: 1/90s, ISO: 800, no exposure compensation, sharpness: hard, contrast: hard, saturation: normal, and, of course, a fixed aperture of f12.5. I'm not sure whether I had any in-camera noise reduction turned on. I have resized it to 1204 x 798 using Microsoft Office Picture Manager, but have not otherwise edited it (I am offshore, so I don't have enough bandwidth for large attachments). The EXIF information on the uploaded photo may been stripped off by Picture Manager.

Regarding soft, I mean that the subjects in the images are not as sharp as with my FA* 400mm f5.6, i.e., fine details are not as apparent with the scope as with the lens. I don't know whether that falls under the definition of focus or sharpness.

I recall seeing a few pictures somewhere in Pentaxforums taken with the PF-CA35 and one or some of the Pentax spotting scopes. Unfortunately, there is no sub-form on Pentaxforums specifically for Pentax sport optics. Try searching the keyword "digiscoping".

Oh, and yes, the PF-65ED with the PF-CA35 has a focal length of 750mm with an aperture of f12.

Cheers

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12-12-2014, 01:58 PM   #5
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QuoteOriginally posted by Ohmic Quote
I haven't posted before, but I've been following the forums for about a year.
Welcome to the forum, it's good your speaking to us all at last.

I'll let the real experts around here answer your question, as I'd be the first to admit that O don't have a scoobie.
07-05-2016, 08:04 AM - 1 Like   #6
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The PF-CA35 comes from a time when there were no dslr. It is made for 24x36mm. Therefore with APS-C you will only get a small crop onto your sensor. Regarding the long focal distance and bad seeing (shimmering) many pictures won't be as good as expected.

On my german website, I have a tutorial for digiscoping. There is a page about the PF-CA35. Even though you might not understand what is written there, the pictures show a lot. Pentax Digiscoping Adapter PF-CA35 Digiskopie

Beneath this title 'Pentax Adapter am Zeiss Spektiv' you can see a comparison of pictures. The left was taken with a Pentax K-3 with the 2,8/40mm behind the eyepiece. The image on the right side was taken without the eyepiece and without the 40mm lens but with the PF-CA35 on 35mm film. I used an old PEntax K2 because I didn't have a FF DSLR for the test. Clearly you can see that the PF-CA35 is made for 24x36mm.

As you can see on that webside, I have combined the PF-CA35 with the lens of a microscope. There are many different of those. With some of them combined with the PF-CA35, it is possbile to make good pictures.

Tom
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