I have found that a 75mm to100mm adapted lens on the Q is about as long as I am comfortable shooting with hand-held. Above that length the size and weight kind of defeat the idea of the Q being a small camera and framing is a real challenge. Recently, I picked up a Navitar 100mm f2.8 machine vision lens on eBay and I thought I'd compare it to other lenses I have of a similar focal length. My criteria were center sharpness, edge sharpness, contrast and fringing. I wasn't too concerned with distortion or vignetting—usually no problem on a small sensor at these lengths.


Here are the subjects:



Top row: 06 zoom (a little short for this test but I used it as a known quantity), Navitar 100mm f2.8, Canon LTM 100mm f3.5, Navitar 75mm f1.3, and Ampex 75mm f1.4. The bottom row (shown without K to Q adapters) is 90mm APO-Rodagon APO (adapted) SMC-M 100mm f2.8, Pentax 50-200 zoom, and an old film-era Tamron 28-200 zoom. You can see the comparative sizes; although the Navitar 100 is the smallest of the lot it wasn't really designed to be used on a hand-held camera—the focus ring is very stiff and there were no grips on it when I got it. It does work, however, and the test I made with it looks OK (click through for detail):



Decent sharpness edge and center, good contrast but severe fringing (above image was after removing most of it in PS.)

For a comparison, here is the test from the APO—Rodagon 90mm f4.5 (click through for detail):



The other lenses had their own characteristics: the 06 zoom (@45mm) had the highest contrast but was a little soft on the edges. The Canon LTM has good edge sharpness (as would be expected from a full-frame lens) and average center sharpness, contrast and fringing. The 75mm Navitar f1.3 was very good in all respects as was the 75mm Ampex (Cosmicar) except for some fringing. Of the Pentax K mount lenses only the SMC-M100mm f2.8 was usable, although a little low in contrast. The zooms, as to be expected, were awful with the Tamron poor in every respect. The top performer was the APO-Rodagon. This is an enlarging lens that I spliced into a de-glassed SMC M 50mm f2. With the adapter and hood it becomes kind of unwieldy although I have used it with extension tubes for macros.


In spite of the fringing, I think I’ll find a use for the Navitar 100mm. It is really small; a perfect lens to have in your pocket on a walkabout.

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Last edited by Unregistered User; 04-28-2019 at 12:39 PM. Reason: typo

[PJ1]

Very interesting. It is easy to get carried away with the crop factor but experimentation soon shows which lenses are useful. I think micro contrast is critical for adapted lenses.

The Q system is defined by size, any really big lens on it tends to defeat the purpose. That said, the APO-Rodagon shows how much potential there is in the Q-S1 and Q-7 sensors, but there is no free lunch when it comes to size/performance ratios, only acceptable compromises. The Navitar 100mm is small and sharp but has a definite problem with fringing. I also have the Pentax Auto 110 70mm which is only okay overall (it also suffers from excess fringing) and is a fixed aperture lens making it not as versatile. The Cosmicar 75mm has the smoothest rendition (lack of micro-contrast?) that makes it my first choice for portraits.

The Navitar 75mm is probably the best lens overall but it is heavy, as to be expected for its speed. The idea of a f1.3 340mm FOV lens (with the DOF of a 75mm lens) is mind-blowing.

[barondla]

The Q system is defined by size, any really big lens on it tends to defeat the purpose.

Defeats the purpose of a small carry camera. Doesn't defeat other uses - like tele monster. My most used and irreplaceable set up is a Q/Q7 on a Pentax DA 300 f4. Which is still small vs a 1500mm+ lens on a PKA body.
Thanks,
barondla

Defeats the purpose of a small carry camera.

I have found that a 75mm to100mm adapted lens on the Q is about as long as I am comfortable shooting with hand-held.

I know what you're saying but this thread is for a hand-holdable telephoto. I've used a 300mm telephoto on my Qs and for me I really need a tripod, even my 135mm is pushing it.