[Frank29]

Thanks everyone. I didn't delve much into the medium format/FF focal length debate. But I think the DFA 150-450 is a good option. KEH and MPB have none, nor any DA560s. I imagine they are pretty rare on the used market.

Another thought (which could fire a debate) What if I bought a used Canon 5D Mk II for about $500 and a used long Sigma or Tamron for that? Then I would also gain better video capability than I currently have.

I know, it's sacrilege, on a Pentax forum, and I could be starting a trip to the 'dark side', but it's an interesting alternative.

Frank

[luftfluss]

$2K USD gets you a Nikon D500 + 200-500/Sigma or Tamron 150-600. That was the route a number of Pentax users took.

Keep in mind the Canon 5D Mk II was introduced 13 years ago. A used one will be a pretty old camera.

[Driline]

Thanks everyone. I didn't delve much into the medium format/FF focal length debate. But I think the DFA 150-450 is a good option. KEH and MPB have none, nor any DA560s. I imagine they are pretty rare on the used market.

Another thought (which could fire a debate) What if I bought a used Canon 5D Mk II for about $500 and a used long Sigma or Tamron for that? Then I would also gain better video capability than I currently have.

I know, it's sacrilege, on a Pentax forum, and I could be starting a trip to the 'dark side', but it's an interesting alternative.

Frank

On the Fuji forums many are using a teleconverter and the Canon 100-400 Mark II lens. It renders better than Fuji's 100-400mm. Just a thought.....

[Steve Horstmeyer]

For astrophotography, mainly sun and moon shots and slow-moving or stationary nature subjects I use both the SMC Pentax-M* ED IF 800mm (f/6.7) and 400mm 9(/4) lenses on Sony FF and Canon APS-C bodies.

These lenses are phenomenally sharp and have no chromatic aberration and I have used both with two 2x teleconverters with no degradation of image quality.

On a FF camera the equivalent focal lengths are approximately 1600mm and 800mm respectively. With two 2x converters you have equivalent focal lengths of 6400mm and 3200mm. This is great for subjects that are not light limited like a full moon or the sun (with the appropriate filter). Both moon images are with the 800mm and two 2x converters with a behemoth tripod and head.

Obviously because the 800mm lens weighs 14.3 pounds and with the converters tops out over 15 and is too large to work with a Wemberly gimbal head, this is not a lens for birds in flight. The 400mm lens is 8.1 pounds and does not fit on the Wemberly gimbal head either. For static shots or birds on a limb or resting zoo animals, if you can bear carrying either, the results are great.

The 300mm ED IF is just as sharp and only 3.6 pounds.

The Pentax 645 format ED IF lenses are just a good.

Attached Images

   

[RICHARD L.]

On a FF camera the equivalent focal lengths are approximately 1600mm and 800mm respectively

No, the P67 800 mm lens has an 800 mm Focal Length on FF and the P67 400 mm has a 400 mm Focal Length on FF. These lenses are very rare and very expensive, being highly corrected, and they produce an aerial image with a diameter of 90 mm. The 800 mm becomes a "1600 mm" with one 2X converter and a "3200 mm" with two 2X converters. The 400 mm similarly becomes an 800 with one converter and a 1600 with two. Maybe Bernard Dery, an optical engineer, might explain this more simply.


P.S. I shot P67 film cameras for over 20 years and now I use my 12 P67 lenses on a Pentax 645Z digital.

[Rocketvapor]

I've use my 6X7 lenses on an APSC K-r.
The 105mm radioactive lens seems to be pretty sharp, the 300 (and a 2x sometimes) is a bear and needs a sand bag for support.

Now that I have a K-3ii I'll have to see if the extra pixels exceed the lens sharpness.

I mention the 300 67 as it is dirt cheep and a worthwhile experiment.

Come on, how bad can a hundred dollar lens be?
(needs a $50 adapter)

Another 2 cents
All my 300mm lenses have the same mag and field of view with my 1.5 crop factor cameras.

[RICHARD L.]

P67 lenses are "sharp enough" for the 50 Mpx sensor of the 645Z.

P67 165 mm f/2.8

P67 90 mm f/2.8

P67 45 mm f/4

[Rocketvapor]

Pixel pitch of the 645Z is 5.32um, close to the pitch of the K-r,
it's 3.88um on the K-3ii.

But I still suspect a good lens will Hold up.

My current old 6X7 300mm has a little fungus from being left in a box in the garage.
In 6X7 I have a 105, 165, 200 and the 300, and two 2X TCs.
I got the 105 cheap (really sharp lens) because it was yellowed. Took care of that easily enough.

I have a newer 300 coming from Japan for just over $100 bucks.

It will have to suffice until the next stimulus round
Nice pics BTW.
Even the extra ones you posted.

[RICHARD L.]

P67 lenses are the "Major Leagues" of medium-format lenses. They cover a very wide field (aerial image of 90 mm or more), produce lovely, true colors and exhibit "deep" contrast. They do not veil or ghost when shot against the light source. It's true they are heavy and manual-focus only but are built to last a lifetime.

P67 75 mm f/2.8

P67 90-180 mm f/5.6

P67 75 mm f/2.8

P67 90-180 mm f/5.6

P67 105 mm f/2.4

P67 105 mm f/2.4

P67 55 mm f/4

Plus you can find huge P67 telephoto lenses too ... lol !



P67 500 mm f/5.6

[Rocketvapor]

Love the rifle sights on the 500
Don't have one of those.

The 300mm might not receive the best reviews, but for anyone thinking about testing out a longer lens, I'll say it again,
How bad can a hundred dollar lens be?
And if you don't like it, sell it.

[Lowell Goudge]

Please stop the discussions and comparisons of other formats to what the op is shooting. It is a waste of everyone’s time, because the OP does not know anything about other formats, especially medium format cameras, therefore references betweeen 645 or 6x7 cameras and lenses on full frame are useless and confusing. Go back to the basics, focal length is focal length. Image magnification is a function of focal length and subject distance. That’s all

[RICHARD L.]

I used a regular 300 mm f/4 almost 25 years ago. On 6X7, it vignetted badly up to f/8, showed green/purple color aberrations and didn't have a tripod mount, making it difficult to handle because of its weight. Of course all of those deficiencies are without consequences on a smaller sensor as you exploit only the center of the aerial image. I sold it and got the M* 300 mm f/4 for over 1000 $. All my gripes were alleviated then : extraordinary sharpness, no CA, tripod mount, I couldn't be happier.

Regards

P67 M* 300 mm f/4 @ f/8 on Ektar 100

On a Pentax 67 II film camera, the M* 300 mm had only the field of view of a 135 mm lens on FF.

P.S. Sorry Lowell, I have finished this aparté. I may seem overly enthusiastic when someone mentions medium-format optics ... Back to the original OP question, please.

[bdery]

No, that's incorrect. The FoV of a 645 300mm on a K-1 will be ~468mm, because only 64% of the available diagonal FoV of the 645 Lens are used by the K-1.

So there's a crop-factor for the FoV of a 645 lens on a K-1 of ~1,56x.

That is not true. Focal length is a property of the lens, not the sensor.

You're confusing field of view and focal length. The field of view of a 300mm will be different on a 645 and a 35mm sensor (as long as the lens covers the 645 format of course).

The better way to see this is to understand that using a FF sensor, comparing a "300mm designed for FF" and a "300mm designed for 645" will deliver the exact same image.

[vijaykishan]

The better way to see this is to understand that using a FF sensor, comparing a "300mm designed for FF" and a "300mm designed for 645" will deliver the exact same image.

This I agree , I did not somehow manage to put that thought in a simple manner that you have done - Thank you.

[vrphoto]

um - what camera does OP actually have?
If K1, I'm under the impression that the x1.4 converter is incompatible.

Also, where is OP intending to photograph wildlife - that is, how portable does the equipment have to be?