Pentax 6x7 Lenses w/ adapter - Worth it? Experiences?

cputeq · 07-26-2008, 09:04 AM

I have been looking into perhaps getting some older lenses in 6x7 format and using a 6x7 -> K adapter for them to use on my K20D. I was wondering if anyone else has experience with them?

Pentax | 67 Lens to Pentax 35mm K-Mount Body Adapter | 37954

Here is the adapter I am thinking of. Apparently you cannot use "A" on the aperture, which is fine since many of the lenses I am looking for don't have an "A" anyway. They also note you cannot use open aperture metering, which shouldn't be a problem since you cannot use "A" anyway, right??? I think I am understanding this right - I could just use "M" mode with green button?

There are several decently priced 6x7 lenses on the market -- Currently I am looking at SMC Pentax 300mm F/4 lenses.

I figure with the lenses being medium format, I could keep aperture at F/4 and have very sharp images on APS-C cameras.

For about $550 I can get this combo -- both the lens and adapter - no autofocus or autometering, but perhaps worth the $700 savings over a DA* 300mm f/4?

Does anyone have experience using 6x7 lenses with adapter? Is the IQ worth the loss of AF / metering?

Would anyone else actually do this or is it not worth the hassle?

jslifoaw · 07-26-2008, 09:32 AM

keep in mind how large the 67 lenses are. you might be better off finding a K300/4 for around 300, or an A*300/4 for roughly the 550 you say you'd spend on this combo (with automatic aperture to boot).

cputeq · 07-26-2008, 09:55 AM

Originally Posted by jslifoaw

keep in mind how large the 67 lenses are. you might be better off finding a K300/4 for around 300, or an A*300/4 for roughly the 550 you say you'd spend on this combo (with automatic aperture to boot).

Thank you for your reply!

As for size, I am really not worried about size or weight ;-)
(actually weight is good, I am working out more to improve fitness).
I do not anticipate having to be very mobile using this combo.

Really what I am worried about is IQ, price, and availability.

I searched a lot and cannot find any A* 300mm f/4. or even SMC-K 300mm f/4 lenses

I am currently using Ebay.com, ebay.co.uK and I think B&H photo to search for used lenses, along with the Marketplace here of course.

I will continue to search, though, as I'm interested in getting perhaps older lenses for longer reach, though I have to wonder just how much IQ I would gain (if any) over my current DA 55-300mm

With something like 645 or 6x7 lenses, I feel I will be able to get awesome IQ wide open since they're larger lenses. STill I will have to research more, thank you for your input.
I'm also researching 400mm lenses -- I like to do nature occasionally, and if I can find a decent 400mm + older lens that would be awesome.

pntxjack · 07-26-2008, 11:46 AM

Hi CPU,
I have used 67 and 645 lenses on the 35mm/Digital Pentax SLR.
67: 600mm f/4 (Awesome sharp and contrasty and HEAVY-that is why I gave it up--took two to carry it.) Also the 165mm and 105mm.
From the 645 format I have used many, most notably the 6oomm f/5.6. Awesome too, though not quite as contrasty, and not quite as heavy, but still too heavy.
Here is what I think--don't know if I made this up or read it somewhere:
The larger format lenses are designed to cover a much larger image size than that on a 35mm/DSLR. So, you are using only the center (sweetest part) of the lens. Tack sharp. If there is any gripe at all, it is that the 67 600mm f/4 is too sharp!!!
If you can stand the weight, you will love 'em.
You will also catch a bit of attention with your cannon mounted on a tripod with your little DSLR hanging off the end.
Enjoy.
Jack

ryan s · 07-26-2008, 12:36 PM

Seems like a solid reasoning.

For me, I'd only do it if I were going to use a 67 camera. That's the reason I won't buy any DA lenses, since they can't be used with (most) film cameras.

*Wheatfield* · 07-26-2008, 02:36 PM

This was shot with the SMC Pentax 6x7 300mm f/4 handheld on the K10. I don't recall any of the technical data offhand.
The smaller picture is a 100% crop. It's not crispy sharp like a lot of the stuff I see floating around here, but it's not bad for a handheld very long telephoto shot. I wouldn't want to hang this lens off a tripod mounted K series camera body, I think it is just too heavy.
My F*300/4.5 is quite a bit sharper than this, and is much smaller.
It also has a tripod mount, which I don't use.