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07-12-2014, 05:57 PM   #1
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Pentax-A* 645 300mm F4, a good choice for budget telephoto?

Hey guys! I'm in the market for a wide-aperture telephoto prime, to be paired with a K-5. I'll have many uses for a telephoto lens, especially wildlife photography, and am willing to try manual focus.

The DA* 300mm f/4 is out of my price range. I can't even rent this lens (I'm in Canada).

I could be convinced to pay $400+ if the quality is significant, and I see that the SMC Pentax-A* 645 300mm F4 can be found in that range, although I would have to purchase an adapter to use on the K-5. Reviews indicate the optical quality is quite excellent, and with the prices of the M* and A* 300's higher right now, the 645 is looking pretty good.

Can someone who has tried this lens tell me if they think it would be worth the extra $250 over something like the SMC Pentax 300mm F4?

I'm open to all suggestions, but stand firm on having a usable aperture of at least f/4. Thanks

07-12-2014, 06:02 PM   #2
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I honestly wouldn't bother- the 645 lens is huge and the adapter will disable both auto-aperture support as well as open-aperture metering. If you can't settle for something like the the DA 55-300mm, then I'd say the K300mm or perhaps a third-party K-mount prime would be worth pursuing.

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07-12-2014, 06:13 PM   #3
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Thanks, Adam. The weight is a consideration but not a deal-breaker. Is there an auto-aperture lens that might work as an alternative? It seems the cheaper SMC Pentax 300mm F4 lacks the A setting too, and doesn't have the same optical quality. I'd love to be convinced otherwise, as I'm just going by reviews and test pictures, but the CA looks pretty bad on the SMC. :-\
07-12-2014, 06:37 PM   #4
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You would need an A level K-mount lens.

I'm with Adam. The cheapest reasonable 300mm is a used DAL 55-300. If you wanted cheaper than that ($200?), I'd guess that the 50-200 cropped down to 300mm would give you better results than the SMC's. On sharpness tests the SMC's might do OK (or might not...) but when it comes down to shooting things at 300mm, A/F and A/E generally trump minor sharpness, and the old telephoto glass usually PF's terribly.

At F/4 though you're out of luck. Everything is $1000 ish, though uou might be able to get a Sigma 100-300 for a bit less than that.

07-12-2014, 06:49 PM   #5
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Ouch, the K-mount SMC is that bad, eh? I have the 55-300, and it was fine for what it was, but even before I damaged it it wasn't capable of the sharp, shallow DOF results I'm hoping for (gave it a knock a couple years ago, and I think it's been fuzzier ever since). I also felt the AF wasn't great at the long end, and that I did better manually focusing anyway, which is why I thought I might get away with a higher quality glass with fewer features. I admit the lack of A/E would cut down on the usable shots, but at the moment I wonder if the K300 might still be better than nothing. Hmn. Thanks for your input!
07-12-2014, 06:59 PM   #6
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QuoteOriginally posted by DK77 Quote
Ouch, the K-mount SMC is that bad, eh? I have the 55-300, and it was fine for what it was, but even before I damaged it it wasn't capable of the sharp, shallow DOF results I'm hoping for (gave it a knock a couple years ago, and I think it's been fuzzier ever since). I also felt the AF wasn't great at the long end, and that I did better manually focusing anyway, which is why I thought I might get away with a higher quality glass with fewer features. I admit the lack of A/E would cut down on the usable shots, but at the moment I wonder if the K300 might still be better than nothing. Hmn. Thanks for your input!
I think a lot of other people would rate it much higher, so take my thoughts with a grain of salt.

I don't know about a damaged 55-300, but I'd much rather use an 'average' 55-300 than the SMC 300.
07-12-2014, 07:16 PM   #7
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Nonetheless, I appreciate your thoughts. :-)

07-12-2014, 07:37 PM   #8
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QuoteOriginally posted by DK77 Quote
I'm open to all suggestions
Just use your favorite K-mount nifty-fifty on a Q!
07-12-2014, 07:46 PM   #9
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I have used a smc DA55-300 and now have a HD DA55-300 WR. I have been very happy with both the lens, and what they can produce.

I also have a M*300/4 which, whilst relatively heavy and a bit bulky is a nice piece of glass and can produce very nice images. This lens is not that expensive and worth considering if you don't mind manually focussing. It also works very nicely as semi auto focus lens with the Pentax AF 1.7x tele convertor
07-13-2014, 09:50 PM   #10
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QuoteOriginally posted by lytrytyr Quote
Just use your favorite K-mount nifty-fifty on a Q!
Haha! That is a different suggestion.


QuoteOriginally posted by NZ_Ross Quote
I have used a smc DA55-300 and now have a HD DA55-300 WR. I have been very happy with both the lens, and what they can produce.

I also have a M*300/4 which, whilst relatively heavy and a bit bulky is a nice piece of glass and can produce very nice images. This lens is not that expensive and worth considering if you don't mind manually focussing. It also works very nicely as semi auto focus lens with the Pentax AF 1.7x tele convertor
Thanks! That M* does indeed look great, but it's out of my range right now. Sigh. Maybe I will have to settle for another 55-300.
07-13-2014, 10:36 PM   #11
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QuoteOriginally posted by DK77 Quote
Thanks! That M* does indeed look great, but it's out of my range right now. Sigh. Maybe I will have to settle for another 55-300.
Keep your eyes open, I got mine on the PF Marketplace a while back for a very fair price - less than I thought it would be.
07-14-2014, 11:49 AM   #12
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I have used the K300/4 successfully for years, along with the 1.7x autofocus adaptor. The A300/4 for the MF camera is likely similar where it counts the most, that being the fringing etc when you miss even slightly the focus.

I would not pay the premium over the K300/4 personally
07-14-2014, 11:50 AM   #13
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My Tamron 70-300mm f/4-5.6 LD Di is very decent and a mint copy only cost me 80 dollars. Sharpness is pretty good, I think, and color rendering is not quite as good as Pentax lenses but it's something you can work with in PP. Also, it's a full frame lens. It gets a bit softer towards 300mm but still very useable - and good at f8. At around 200 it's still very sharp. Even 270mm looks pretty good to me.
Earlier versions of this lens had tons of purple fringing but I find that this Di version (coatings for digital sensors) pretty much solves the issue. Also, the AF hunts in low light so focusing manually is necessary sometimes, but it's not bad to MF this lens.

For low light or when I don't need AF I have a SMC Pentax-A 70-210mm f4 which is a good lens wide open and very sharp at f/5.6 throughout the range. Colors are wonderful, to me at least. It even doubles as my portrait lens sometimes, it's got some magic at 70-100mm for someone like me who's never had limiteds or * lenses. It can usually be had for around 70 dollars. Downside is manual focus (it's pretty easy actually), and purple fringing is worse than the aforementioned Tamron.

That would be my suggestion for low budget tele work under 200 dollars - just combine these two lenses, they'll both still probably be lighter than that 67 monster
07-14-2014, 01:12 PM   #14
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QuoteOriginally posted by DK77 Quote
Ouch, the K-mount SMC is that bad, eh? I have the 55-300, and it was fine for what it was, but even before I damaged it it wasn't capable of the sharp, shallow DOF results I'm hoping for (gave it a knock a couple years ago, and I think it's been fuzzier ever since). I also felt the AF wasn't great at the long end, and that I did better manually focusing anyway, which is why I thought I might get away with a higher quality glass with fewer features. I admit the lack of A/E would cut down on the usable shots, but at the moment I wonder if the K300 might still be better than nothing. Hmn. Thanks for your input!
I had the old K SMC 300/4 in the past. It is big, heavy and shows very strong CA and purple fringing. I sold it off and got an A* 300/4, which is a wholly different beast. Sleak, relatively lightweight (considering its all metall construction and old fashioned optics) and focuses nicely, if one doesn't need AF. Fringing and CAs are not an issue and a slight remnant fringing can be easily removed, without destroying sharpness. Overall it is a very sharp lens and well-worth the extra money over the old K version.

Besides that, the old K desperately needs a tripod ring, which isn't available (except for a plastic thingy by a hobbyist, which flexes too much), whereas the A*, due to its much reduced weight and bulk excerts much reduced torque on the camera mount and can be used on a tripod, without fear of tearing out the mount off the camera body.

Ben
07-14-2014, 06:48 PM   #15
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I've also got a 645 A* 300/4. It's an excellent, sharp lens, in a different league entirely than the K-mount M 300 I had years ago. You can also use it with the matched 645 1.4x and 2x teleconverters. Results with the 1.4 TC, giving a focal length of 420mm, match the quality I get with Canon's L 100-400 at 400mm on a 7D.

That said, it's not an easy combination to use. Manual focus is tricky on a crop-body camera, meaning you miss a lot of shots, and Pentax's in-body shake reduction simply isn't as effective as Canon's built-in IS at longer focal lengths. I've also tried it with the 1.7x AFA converter. It works, but again, you're probably better off in the long run with real autofocus for the kind of subjects (birds, wildlife) long lenses are usually wanted for,

See examples here.
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