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12-21-2013, 09:48 PM   #1
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just got DA 50mm f1.8 maybe should get FA50mm 1.4 insted?

DA is not tack sharp till stepped down to around f2.5 on K-5II. kind of first prime so pardon my ignorance.
I wonder if this is "normal". how is the FA 50mm f1.4 performing? i know the price difference is quite steep but im willing to pay the difference if FA is much better than DA. Any users of both that could chime in I would appreciate it.
Thank You

12-21-2013, 09:59 PM   #2
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It may be a focus issue. Fast 50s have a very shallow DoF when used wide open.
12-21-2013, 11:11 PM   #3
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If you expect the f/1.4 to be sharper wide-open than the f/1.8, you will be disappointed. The Pentax 50/1.7-1.8 family of lenses have generally been the "sharp" ones, while the 50/1.4 family were the "fast" ones. Some say the 50/1.4 doesn't get sharp until around f/4.
12-21-2013, 11:43 PM   #4
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QuoteOriginally posted by dronek75 Quote
DA is not tack sharp till stepped down to around f2.5 on K-5II. kind of first prime so pardon my ignorance.
I wonder if this is "normal". how is the FA 50mm f1.4 performing? i know the price difference is quite steep but im willing to pay the difference if FA is much better than DA. Any users of both that could chime in I would appreciate it.
Thank You
Tack sharp at F2.5 is already pretty good Most fast primes aren't really sharp until they're stopped down by 1-2 stops.


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12-22-2013, 01:05 AM   #5
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As already said, the FA50mm f1.4 is not the answer. In fact the FA50mm f1.4 has a 'reputation' to be somehow soft. As pointed by THoog, the FA50mm f1.7 (and earlier variants) is much sharper.

However, if you want a fast 50mm that is sharp, I would recommend you to consider the Voigtlander Nokton 58mm f1.4. The lens is a tank, very solid, but also to provide superb image quality (IQ). Although MF and no longer maufactured in Pentax mount, you can regularly find it on the market place.

Have both the FA50mm f17 and Voigtlander Nokton 58mm f1.4. The VL58mm f1.4 is my 2nd most used lens, after my DA18-250mm and before my FA31mm Ltd. The FA50mm f1.7 is Ok but the VL58mm is a rare beauty.

My 5 cents, hoping that it may help.
12-22-2013, 01:20 AM   #6
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Or the new Sigma...
12-22-2013, 03:02 AM   #7
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I'm in the same boat, slightly disappointed with my DA 50 1.8 wide open but from reading above seems this is normal. I have had to apply some focus adjustment to it as well so worth you checking that out.
12-22-2013, 04:39 AM   #8
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Even the DA*55 is not tack sharp @f1.4, but really is @f1.8 ... but it is much more expensive !

Also, keep in mind that very good lens wide open are usually very big.

12-22-2013, 04:46 AM   #9
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My FA 50 1.4 is very sharp at f1.7 and sharp wide open with a hood. I've had tons of fifties, 1.7, 1.8, 1.4... Not the DA, though. Kept the FA 50 1.4.
12-22-2013, 04:51 AM   #10
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I own the Tak 50 1.4, the K 55 1.8, and the Sigma 50 1.4. The Sigma wins hands down in every respect.
12-22-2013, 04:55 AM   #11
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So yeah, classic sharpness blues.
At f1.8, the DoF is very shallow, so its very easy to see it as "soft", and misfocusing is easy, too. Focus and recompose technique is almost impossible at that aperture
The other problem could be high ISO or slow shutter, as either of those can make the photo less defined/blurry.
Adam also pointed out something important. 99% of lenses are poor wide open and only improve when you stop down. If you buy the DA 35mm f2.4, it will be quite good wide open, but it will be better yet at f4.0. Similarly the DA 50mm f1.8. It is still brighter, though, because even when stopped down, it will be a wider aperture than a slower lens stopped down. And in a pinch, you can still use it wide open.

Also, keep in mind things like white balance and light quality. Light balance can drown out some detail. And if you have poor light conditions, you cannot get a lot of detail/sharpness. A lens hood can also improve IQ, by increasing contrast and reducing flare (lots of people highly recommend a good lens hood as the first step to improve IQ). For optimal sharpness you almost have to use a tripod with 2sec timer/remote trigger, and possibly a flash or two. But considering bang for buck, the DA 50mm should offer you a lot, and is not any worse than 50mm lenses of similar cost from other brands. However, if you insist, you can buy a M 50mm f1.7 - all manual, but very sharp and almost inexpensive. (but even this highly regarded 50 is still not that great wide open)
Maybe the only way to get perfect wide open results is a lens like the Zeiss Otus But it is manual focus and costs around $3900
12-22-2013, 06:26 AM   #12
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Only my DFA 50mm is sharp wide open, but it's f/2.8 :-D
but I am using my DA easily @f/2 onwards. And I had SMC-A 50 f/1.7 which regarded as a sharp fifty, but that was soft wide open also.
12-22-2013, 12:03 PM   #13
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Focus with live view and see if it is any sharper. If not, then it is what it is. My experience with the FA 50 f1.4 is that it gets sharp around f2.8. DA *55 is a lot sharper, although I don't usually shoot it wider open than f1.8.
12-22-2013, 01:22 PM   #14
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My FA is very sharp from f2.8 too. Sigma should be sharper lens in f1.4 but its muchbigger size.
12-22-2013, 02:31 PM   #15
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Good point! Live view, maybe with focus peaking, can help you nail the focus. Some photographers go so far as to get a different focusing screen, split prism or something, for easier MF and focus verification.
Also, using a focus chart and doing an AF adjust can help you out. That is, provided the problem is focusing.
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