Pentax PF80 questions (1 Viewer)

Kevin Conville · Feb 27, 2008

Hi everyone,

I've looked but haven't found the answers I'm looking for.

I have a PF80 scope. I also have a Canon S70 digital camera and a Canon 350D/Digital Rebel DSLR with a Canon EF-s 60 macro lens that is probably the best suited (of the lenses I have) for digiscoping.

I'm confused as how to get started. Pentax' photo adapter for an SLR could work for me (I suppose) with an EOS/Pentax mount adapter, but they're expensive and I don't know what quality they yield. According to Pentax, that device makes for an F12 1000mm lens equivalent.

The other way to go, I've summized, is shooting through an eyepiece. It seems there are threaded adapters that connect the front threads of a lens to the threads of an eyepiece? I'm using a Pentax XW14 eyepiece on the scope now and can't imagine how this works.

I'm also open to the idea of using the S70, but again I don't really grok how these things attach. I've seen a few of the Rube Goldberg devices that hold the camera with an articulated arm but they look awkward and slow to use, to me. Am I wrong? I'm much more inclined to use the DSLR however, as it has much better high ISO performance

Any Pentax/Canon people out there doing this and do you have any photos depicting your setup? Open to all ideas.

Many thanks in advance for your help.

-Kevin

Sout Fork · Feb 27, 2008

Kevin Conville said:
Any Pentax/Canon people out there doing this and do you have any photos depicting your setup? Open to all ideas.

Many thanks in advance for your help.

-Kevin

I use the Pentax SLR camera adapter with a pentax camera and the Pentax 100mm spotter. Don't know how well this would work with any other camera then a Pentax because the adapter terminates in a Pentax K mount and you would need some kind of adapter to get from that to your Canon.

Can't help you with any other method.

Pic taken with this setup ...

Kevin Conville · Feb 28, 2008

Thanks Soutfork,

It's too bad Pentax didn't make this this photo adapter with a universal thread that would allow different T-mounts to be attached for the various bayonet mounts.

I'm OK though as I have a Canon EOS DSLR and this mount allows the use of quite a few other maker's lenses to be attached with simple mount adapters. Something to do with flange to sensor depth and the width of the mount opening.

How is that setup in practice? Is it slow to focus at F12? Your Bald Eagle shot looks good but are you generally happy with the image quality?

Sout Fork · Feb 28, 2008

Kevin Conville said:
Thanks Soutfork,

It's too bad Pentax didn't make this this photo adapter with a universal thread that would allow different T-mounts to be attached for the various bayonet mounts.

I'm OK though as I have a Canon EOS DSLR and this mount allows the use of quite a few other maker's lenses to be attached with simple mount adapters. Something to do with flange to sensor depth and the width of the mount opening.

How is that setup in practice? Is it slow to focus at F12? Your Bald Eagle shot looks good but are you generally happy with the image quality?

I don't know for sure but I would think it would be possible to get an adaptor with a Pentax body mount on one side and a male T thread on the other. That way you could use any conventional T ring on the Pentax camera adapter that you wanted. A more direct method would be an adapter with a Pentax body mount on one side a Canon mount on the other. I don't know if such an adapter is even made however.

I don't find the focus slow. However I'm old school and very comfortable using manual focus. I would never use AF for wildlife - it just isn't accurate enough in my opinon.

As to quality judge for youself. All of the following were taken with this setup.

mmdnje · Feb 28, 2008

One thing is to use the dedicated pentax adapter. You may want to consider this product:
http://www.amazon.com/gp/product/B0...TF8&coliid=I31AISE9QE8T9E&colid=1L04DBY50KT50.

Another thing is to use your camera/lens combo attached to your Scope/eyepiece combo. All you need is a step ring to do this. using the XW14 and a 60mm lens will produce too much magnification, which in turn would result in blurry pictures. I would suggest a 28mm lens, or 50mm maximum.
I agree with Sout Fork that manual focus is the way to go for this approach.
I my gallery ther are some examples using the canon 350D with a 28mm lens attached to the XW20 and PF80A.
JOse

Kevin Conville · Feb 28, 2008

Thanks Soutfork and Jose for your responses.
I'm more inclined to go with the lens/eyepiece method I think.

Jose- I bought a Pentax -EOS mount adapter as your link depicts. Even if I don't use the dedicated Pentax photo attachment I have a few Pentax lenses around here I can try.

You say all I need is a step ring to mount a lens (in your case a 28) to a XW eyepiece. This is where I'm missing something. I've tried unscrewing the eyecup but can't. Can you advise me please? A photo, if you happen to have one, would be great.

The Canon 350D with 28mm lens mounted and attached to an XW20 eyepiece yields what in magnification? Roughly what is it equivalent to in camera telephoto terms, do you know? What are your thoughts of using a 28mm lens mounted to an XW14?

In your photos, very nice BTW, they're showing some vignetting. Is this a by-product of this setup or are you added that for artistic merit?

Sorry for all the questions, I appreciate your help.

ullihoeger · Feb 28, 2008

If I understand the Pentax adapter setup correctly you have to rely on manual focus with it anyway, since there is no objective to do the autofocussing for you?
Specifically with the Pentax scope and it's ability to accept astro eyepieces I wonder if there are other ways to get a digital SLR hooked up to it. I am pretty sure the astro folks have adapters for this purpose.........

UH

mmdnje · Feb 29, 2008

setup

here are some pics of my set-up
The camera is a canon 350D (I use a sony alpha too), the lens is a canon 28mm f2.8. The eyepiece is a pentax XW20mm. If you remove the eyecup (unscrew) it exposes a 43mm thread (2nd pic). Using a 52mm-43mm step down ring i attach the camera/lens combo to the eyepiece, and the put it in the scope.
Hope the pics make sense.Jose

Kevin Conville · Feb 29, 2008

Thank you Jose! Those pics are just what I wanted. Very kind of you to take those for me.

I still have a few questions and I'm sorry I'm leaning on you for this but we have the same equipment and your images are very high quality.

Why the Canon 28mm lens? Is it because after the 1.6x crop factor it is close to a "normal lens" view?

Do you know the magnification of your setup?

What would be the issue (if any) doing the same setup with the XW14? Too much magnification? Does it make the f ratio slower?

Regards,
Kevin

mmdnje · Feb 29, 2008

Q: Why the Canon 28mm lens? Is it because after the 1.6x crop factor it is close to a "normal lens" view?
A: I had looked through a 50mm lens and it was too much magnification. Images were too blurry for my like. I could not find a 35mm lens so I settel for the 28.

Q: Do you know the magnification of your setup?
A: XW20/PF80A=X25 (1250mm). 28mmm lensX1.6 crop factor= 45mm. however the image is slightly cropped so the 'effective magnification" is ~50mm. So in my mind the overall magnification is ~1250mm.

Q: What would be the issue (if any) doing the same setup with the XW14?
A: It may work. But remember that most of the "great" digiscoped pictures you see out there where shot at close distance. (7-15meters)
The less light in the system the higher the f number, so a more powerful eyepice wil result in slower shutter speed.

I hope this makes sense
Jose

Kevin Conville · Feb 29, 2008

Indeed, it makes perfect sense Jose and meshes with what I had figured.
Thanks for articulating these issues and for your photos.

One more question, what f stop do you set the lens at?
I'm guessing somewhere in the middle F5.6 or 8.

Regards,
Kevin

mmdnje · Feb 29, 2008

Actually the lens is usually at f/2.8. I'm still trying to decide if the lens is sharper at f/3.5-4. I read somewhere that in DSLR digiscoping there is no increased DOF if you stop-down the lens; so I usually keep it wide open, to gain some speed also. Whatever you decide to do, please post your results so we can all learn from it. Jose

JGobeil · Mar 3, 2008

Kevin,

I use a setup similar to Jose's and find it quite promising.

See here:
http://www.birdforum.net/showthread.php?t=100519&page=5

I don't have a prime W/A lens so I cannot comment on its use but Paul Corfield seems to have good results with one (see same thread). I also posted formulas to calculate magnification in the same thread.

Good luck with digiscoping
Jules

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