[raider]

Hi Raider,

As far as premium lenses go, I'd suggest a Canon FD 300mm f4 L as one of the best "bang for buck" 300mm primes. An FD2Q adapter can be gotten cheap, and it's possible to find a decent copy of the lens between $300-400 USD. I have one that was converted to K mount by a user. It was in "beater" cosmetic condition, as a previous owner had more than prominently scratched its initials on both the barrel and integrated hood, probably with a dull axe. . .I covered these with electrician's tape, and it actually looks good from a distance. . . in any case, I paid $225 for it IIRC, and have been impressed with the lens' performance. I have 2 FA* 300/4.5s and 1 each Tamron SP 300 f2.8 Adaptall 2, Sigma EX 300 f2.8 APO, and an FA* 300 f2.8, so I am familiar with most of the top end 300mm lenses in K mount. I find the FD 300/4L (maybe not so surprisingly) in the same league optically with the newer premium AF optics. It's sharp wide open (which you want with the Q) and MF is fine and precise. It controls CA/PF about as well as my FA* 300/4.5s. This is better optical performance than you will find in the K, M*, and A* versions of the 300/4 from Pentax at about the same price point or less. Some samples at https://www.pentaxforums.com/forums/136-pentax-q/180716-my-new-long-lens-q.html#post1887982

An alternative, that might be more useful since you have Pentax DSLRs, is any of the DA 55-300 variants. For me, this is possibly the best compromise between optical performance and practicality (carry weight/size and convenience). The zoom capability makes spotting a lot easier than any of the 300mm primes. Optically, it's not up to the same standards as any of the premium primes, but it's not really that far behind. It's usable at both wide open and stopped down to f8 without losing too much to diffraction (which, in reality, isn't nearly as much of a problem as some may postulate). I have found this combo usable handheld with reasonable technique, using a magnifying loupe only to shoot sparrow sized subjects at 10-15 ft and diving birds like grebes and mergansers at much farther distances. Some examples at https://www.pentaxforums.com/forums/136-pentax-q/204091-q-fw-v1-1-da-55-300-h...ml#post2156152 and https://www.pentaxforums.com/forums/136-pentax-q/223850-q-da-55-300-pied-bill...ml#post2374943.

Personally, I own both an original DA 55-300 (with the metal mount) and a WR version, but the original is the one I usually use with the Q as it's zoom ring is considerably freer to rotate, so it's faster to use. I wouldn't shy away from the DA L version for use with the Q, but I'd get one of the aftermarket hoods for it since it does not come supplied with one.

Scott

Thanks Scott. I used to have a DAL 55-300 which I bought off a forumer here. I find that the IQ is not really as sharp as I hope to be and I sold the lens about a year later. I am very surprised to see your sharp photos using the Q with the DA 55-300.

I will investigate that Canon FD300 lens further, plus looking all the other lenses the other guys suggested. But will see if my Tamron 70-200 is useable (or not) with the Q.

[WPRESTO]

If you could find one, the long-discontinued Takumar/Pentax 300 f6.3 is a decent lens, and very compact/light weight. The original S-thread version was preset, but later a version with pin-push auto diaphragm was introduced. I would go for the pre-set. Doesn't matter, as you'd probably be using it wide open 90% of the time. Had one for my Spotmatic and thought the IQ decent, although not up to modern ED glass lenses. My main objection was a very long minimum focus distance, but adding a Canon achromatic 500T close-up filter would cure that.

[crewl1]

Thanks Crewl but I don't think the Tamron 70-200 has an aperture ring come to think of it....do I just shoot wide open with the converter?

Look for a converter that allows aperture control.
On the budget end Fotodiox makes one.
http://www.amazon.com/gp/aw/d/B006NQ9T34/ref=pd_aw_sim_421_4?refRID=101GT6F7XZ9A83MPKE0V

You will need this type for any new style lens.

The Pentax adapter has a wonderful geared dial for aperture (and leaf shutter,) but the Fotodiox is usable to see if you like the concept.

[raider]

Look for a converter that allows aperture control.
On the budget end Fotodiox makes one.
http://www.amazon.com/gp/aw/d/B006NQ9T34/ref=pd_aw_sim_421_4?refRID=101GT6F7XZ9A83MPKE0V

You will need this type for any new style lens.

The Pentax adapter has a wonderful geared dial for aperture (and leaf shutter,) but the Fotodiox is usable to see if you like the concept.

Thanks Crewl. I will be buying the original Pentax OEM converter. It looks like this allows me to adjust the aperture on any DA lens...

[WPRESTO]

FOLLOW-UP. I went on EBAY to see if there were any 300 f6.3 lenses on offer. There were several, prices of (approximately) $45, $160; and $500(!!!!). All were the preset version. It is an S-mount lens, so an appropriate adapter would be required. Several respondents have suggested the old 300 f4 Takumar in its various K-mount versions. I've only seen one IQ test for this lens, and to call the results "disappointing" would be a grotesque understatement.

[boriscleto]

Several respondents have suggested the old 300 f4 Takumar in its various K-mount versions. I've only seen one IQ test for this lens, and to call the results "disappointing" would be a grotesque understatement.

What various K-mount versions? The Takumar 300/4 isn't optically related to the K-mount 300s at all. The Super/S-M-C Tak is 5 elements in 5 groups. The K is 7 elements in 5 groups. The M* is 8 elements in 7 groups. A formula that carried over to the A*. The DA* is 8 elements in 6 groups with 2 ED elements.

The tests I've seen of the M* and A* are not disappointing in the least. The test of the K was with a cheapo Fotodiox.

[raider]

So should we be looking at the M300/F4 and not the Takumar M42 ones? I am not familiar with old Pentax lenses and tend to get these mixed up one way or another....

[WPRESTO]

What various K-mount versions? The Takumar 300/4 isn't optically related to the K-mount 300s at all. The Super/S-M-C Tak is 5 elements in 5 groups. The K is 7 elements in 5 groups. The M* is 8 elements in 7 groups. A formula that carried over to the A*. The DA* is 8 elements in 6 groups with 2 ED elements.

The tests I've seen of the M* and A* are not disappointing in the least. The test of the K was with a cheapo Fotodiox.

Again, I only recall seeing one test of the older 300 f4, and it may have been the original SMC S-mount version. I had one of the S-mount versions for a while, but it was very heavy/bulky. At that time, the 300 f6.3 seemed to have better IQ at the same aperture, but obviously the latter has major limitations being only f6.3.

[boriscleto]

Again, I only recall seeing one test of the older 300 f4, and it may have been the original SMC S-mount version. I had one of the S-mount versions for a while, but it was very heavy/bulky. At that time, the 300 f6.3 seemed to have better IQ at the same aperture, but obviously the latter has major limitations being only f6.3.

This thread has links to tests of the various 300/4s

https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...ce-thread.html

The K was tested using a cheap Fotodiox (unpainted) adapter.

https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...ml#post2247022

https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...ml#post2273920

https://www.pentaxforums.com/forums/136-pentax-q/173602-reach-q-images-39.html#post2272735

[crewl1]

Reminds me that I need to update the index for the new samples posted .

[WPRESTO]

This thread has links to tests of the various 300/4s

https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...ce-thread.html

The two images in the thread above that were taken with an SMC K300 f4 I would classify as having marginal IQ at best.

[boriscleto]

The two images in the thread above that were taken with an SMC K300 f4 I would classify as having marginal IQ at best.

They were marginal photos at best. If I had a K300/4 I would test it with the Pentax adapter...

[crewl1]

The small Q sensor is brutal on lenses so any bad tendencies will be exaggerated.
A lens that might look great on APS-C may not perform well on the Q.

Starting with an excellent lens such as the DA*300 helps.

The index samples give a good indication of expected results.

[Piotrek K]

I tested one more lens today inspired by this thread and maybe found good one that could be purchased really cheap (I bought my copy for about 45 USD including adaptall mount and international shipping).
This is Tamron SP Adaptall 60 - 300 23A (3.8 - 5.4) which I tested today at 300/5.4 with the original Q fitted with generic adapter on the tripod.

The photos below are full frames followed by one 100% crop. They were developed from raw in RawTherapee. These are just boring test images, but I applied standard PP which I use for wildlife photos (including some abberation removal, film simulation (Velvia), use of Topaz Detail and sharpening after resampling to the web size). The abberations are present but not that bad compared to the other old lenses.

Some more crops could be found here: https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...#ixzz3auFc6B9T

[raider]

Thanks for the shots Piotrek. I just searched eBay and Tamron Adaptall 300mm did not get many hits. There are a few Tamron Adaptall 70-200 and 200-500 but 300mm is almost never to be seen. I guess good old lenses is hard to come by.