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04-03-2015, 09:08 PM   #1
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Which 50 to keep? Da vs F 1.7

After not wanting a 50 at all, I've been using a DA 50mm f1.8 for a portrait class and its a nice little lens. Yesterday I picked up a F 50mm f1.7 for a song locally with the intent to resell it... But which to sell? I don't need both, and with a DA 40mm limited and a desire for a DA70ltd in the future (which I could almost afford by selling both 50's) I wonder if either 50 is necessary at all?

WWPFD?

04-03-2015, 09:12 PM   #2
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Sell the F 50/f1.7 to me for a rhyme and a sonnet...

The F 50/1.7 is identical the to M/A 50/f1.7 one of the best normal primes...(I make no secret of being a fan of the F series) It's better built than the DA, (has more CA) I speculate since the front element is somewhat "flatter" than that of the DA it should be sharper edge to edge. Although they're similarly spec'ed expect a 2/3 stop brighter images with the F 50/1.7 and those warm bright vintage Pentax colors....

Last edited by Stavri; 04-03-2015 at 09:21 PM.
04-03-2015, 09:36 PM   #3
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QuoteOriginally posted by Stavri Quote
Although they're similarly spec'ed expect a 2/3 stop brighter images with the F 50/1.7 and those warm bright vintage Pentax colors....
2/3 stop brighter? The F 50/1.7 is only 1/4 stop faster full open and stopped down should transmit about the same light for a given aperture setting. Is there a secret fault to the DA 50/1.8 that sucks light? I don't have the F 50, but I do have the optically identical M and A versions as well as the DA 50. I will have to test this out.


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04-03-2015, 10:17 PM   #4
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QuoteOriginally posted by skierd Quote
After not wanting a 50 at all, I've been using a DA 50mm f1.8 for a portrait class and its a nice little lens. Yesterday I picked up a F 50mm f1.7 for a song locally with the intent to resell it... But which to sell? I don't need both, and with a DA 40mm limited and a desire for a DA70ltd in the future (which I could almost afford by selling both 50's) I wonder if either 50 is necessary at all?

WWPFD?
It's not necessary unless you feel like it is. Which it does not sound like. A 40mm and 70mm is a more versatile combo than a 40mm and a 50mm.

04-04-2015, 03:24 AM   #5
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Get a second body and keep both. Fast 50's are sacred, you know?

My F50/1.7 is my favorite lens. I havenīt tried the 1.8 but they should be close. In terms of performance, sample variation may be a key here. Test both side by side at wide open, f2 and so on and check if one is noticeably better than the other in terms of center sharpness, corners, CA etc.
Another factor is size, weight, looks and feel. That's very subjective and only you can determine how important and which you like better.
Now, the 40/70 idea sounds like a killer combo as well.......

Thanks,
04-04-2015, 04:22 AM   #6
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QuoteOriginally posted by skierd Quote
After not wanting a 50 at all, I've been using a DA 50mm f1.8 for a portrait class and its a nice little lens. Yesterday I picked up a F 50mm f1.7 for a song locally with the intent to resell it... But which to sell?
Both lens use the same optical formula (6 elements in 5 groups). So results should be pretty much the same.

My advise : Keep the F if you are going to use film body, otherwise sell it.
04-04-2015, 06:07 AM   #7
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They're both very good lenses. The DA 50/1.8 has lower chromatic aberration and is a touch sharper in the corners, so if purely image quality is all you're after, sell the F.
04-04-2015, 06:52 AM   #8
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Nothing wrong with the older 50mm. The main draw to the DA 50mm is that you get a brand new lens with modern lens coatings and warranty for.. well, less money than the older, used FA or F series lenses. But other that, the FA and F have more features. Now, optically they might not be any better, but they have distance scales, aperture ring, maybe they come with a lens hood, they have a metal mount and more metal in the actual body of the lens.. Difficult to say which one. Id say look at what is actually available on the used market, maybe you get a good deal. Or look at photos of those lenses and get the one that catches your eye. Or just buy according to least resistance, and get DA 50mm and never look back.
I dont think any of these lenses will disappoint you optically. But think of the features. If you want to use macro bellows or tubes, if you want to use the lens on an older film camera, then you need aperture ring.

Edit: Oh, and yeah, why get rid of one? I have a couple 50mm lenses. Some people have dozens. No problem there, as long a you use them. Sell the one that you use the least, or the one that you can get the most money for (if there is no real advantage)


Last edited by Na Horuk; 04-04-2015 at 07:15 AM.
04-04-2015, 07:12 AM   #9
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I have 3 50's... count 'em the DA 50 f1.8, the M 50 f1.7 , and the A 50 f2.0. Do I "need" 3? Well, no I don't; am I going to keep all three? You betcha I am!
04-04-2015, 09:10 AM   #10
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I've got 3 as well, the A 50 f2, the F, and the DA. Also have a takumar 55 f1.8 with adapter.

The F came attached to a good zx-7, so the aperture ring isn't important.
04-04-2015, 06:03 PM - 1 Like   #11
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QuoteOriginally posted by aurele Quote
Both lens use the same optical formula (6 elements in 5 groups). So results should be pretty much the same.
The designs are similar, though not the quite the same. As carpents noted, the two lenses have different image characteristics.


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04-05-2015, 12:36 AM   #12
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QuoteOriginally posted by stevebrot Quote
The designs are similar, though not the quite the same. As carpents noted, the two lenses have different image characteristics.


Steve
i guess, it's due to the coating, because according to Pentax spec' sheet, both lenses use strictly the same 6/5 design.
04-05-2015, 03:56 AM   #13
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Yeah, I think M 50mm f1.7 all the way to DA 50mm f1.8 have the same optical design. Now, this doesn't mean its the exact same lens. For example, regulations on materials change over time, factories and machining technologies change, employees and workers change, and finally lens coatings change as well. So I do believe when people say the DA has the best flare resistance, and the F is the sharpest (but loudest AF). And they might even have different contrast and slightly different bokeh. But the differences between them will be much smaller than in comparison with.. lets say Sigma 50mm f1.4 or Industar 50-2 (f3.5)

Keep in mind that even something as little as changing metal straight aperture blades for plastic rounded aperture blades will affect the image, in terms of bokeh, starbursts, contrast.. and I think the DA 50mm has rounded aperture blades, right? I know my M 50mm f1.7 would produce quite different bokeh because of its aperture shape:


Cosmic fly sitting on a tree
- Pentax M 50mm f1.7, around f2, f2,8. Dark conditions, very high ISO

The above photo would have a very different look if the lens had rounded aperture blades. Those OoF star-like hexagons would be round.

Last edited by Na Horuk; 04-05-2015 at 05:46 AM.
04-05-2015, 05:36 AM - 1 Like   #14
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QuoteOriginally posted by dakight Quote
I have 3 50's... count 'em the DA 50 f1.8, the M 50 f1.7 , and the A 50 f2.0. Do I "need" 3? Well, no I don't; am I going to keep all three? You betcha I am!
QuoteOriginally posted by skierd Quote
I've got 3 as well, the A 50 f2, the F, and the DA. Also have a takumar 55 f1.8 with adapter.

The F came attached to a good zx-7, so the aperture ring isn't important.
Only 3? I'm up to 22...in 5 different lens mounts...
04-05-2015, 06:09 AM - 1 Like   #15
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QuoteOriginally posted by aurele Quote
i guess, it's due to the coating, because according to Pentax spec' sheet, both lenses use strictly the same 6/5 design.
Whatever the cause, they are quite noticeably different.

We (PentaxForums) are currently writing an in-depth comparison article between the DA50/1.8 and the M50/1.7 and two other 50mm lenses. They're all very good, but the modern DA is without question the best for corner sharpness and CA. If that matters to you, then the DA is 'better'.
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