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08-28-2015, 10:58 PM   #1
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1.7 vs 1.4?

Hey, folks.

After amassing several K and M series bodies, and all the M-series lenses I'm likely to need, I'm looking to winnow the collection down to what I'll actually use. I'll be keeping a black KX and a black K2, and most (not all) of the lenses. I guess the CBA pendulum has swung the other way, and I'm really only interested in fine-tuning my kit to the most useful items.

My question for the fine folks here is this:my normal lenses are M f/2 and f/1.7 (several of each). I have been pondering getting the f/1.4 50's for the KX and K2. Is it worth it? Is there enough difference in the optics or in the final product to warrant such a purchase? Or is the f/1.8 55 better than both? I'm looking for a streamlined kit to grow old with, and I'm looking to trade quantity for quality.

(For the record, I'm not interested in the 1.4 just to say I have one. If it's better, I'm all in, if not, I'll stand pat.)

All opinions are welcome, and I thank you in advance.

08-28-2015, 11:03 PM   #2
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You're probably not going to be able to tell the difference (especially on film) unless you plan to leverage the faster F stop for bokeh.

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08-28-2015, 11:35 PM   #3
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The 1.4 will give you better critical focus, especially in low light. Whether you use the 1.4 f-stop to take a shot is another matter entirely.
08-29-2015, 03:49 AM - 2 Likes   #4
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QuoteOriginally posted by Lenscap Quote
:my normal lenses are M f/2 and f/1.7 (several of each).
Well, then sell some and get one f1.4, just so you can see for yourself, so you can at least say you have one
QuoteOriginally posted by Lenscap Quote
I'm not interested in the 1.4 just to say I have one
Oh. Huh, the f1.4 is not better than the f1.7 in most respects - except that wide open it will have slightly more background blur, "bigger bokeh balls". Some people like its rendering more than the f1.7, say its more creamy. The rendering will be slightly different, because they are different optical designs. This is why some people have so many 50mm lenses. You can try something even more different and get a third party 50mm f1.4. Some are really good and quite different from the Pentax designs, so they will have different kind of bokeh, colours, contrasts.. But if you are looking at just sharpness, then the f1.7 is probably equal or better.
QuoteOriginally posted by Lenscap Quote
Or is the f/1.8 55 better than both?
This is a cool lens that I am thinking about for some time now. Looks pretty interesting, sharp, with nice bokeh, so if you already have plenty of 50mm, maybe you want to try a 55mm for portraiture or something. It has slightly higher magnification, so the bokeh will still be big, despite the "slow" aperture of f1.8


Last edited by Na Horuk; 08-29-2015 at 04:46 AM.
08-29-2015, 06:12 AM   #5
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I have found the M 50 1.4 to be quite a lot better than the M 50 1.7, especially at the wider apertures, once you get down to f5.6 or f8 then there's no difference.
Despite what a lot of other people say I have found that the K 55 1.8 is not as good as the M 50 1.7, also it seems to be getting more difficult to find a K 55 1.8 that hasn't got cloudiness in the rear lens block.

These comparisons were made with 4 different 1.7's, 3 different 1.8's and my one and only 1.4.
I found quite a lot of difference between the different 1.7's due to sample variation so perhaps I haven't yet found the best 1.7 or maybe my 1.4 is exceptionally good.

Incidentally I have compared my M50 1.4 with 2 different Tomioka design 55mm 1.4 lenses and the Pentax beats them easily.

Last edited by Ray-uk; 08-29-2015 at 06:18 AM.
08-29-2015, 07:11 AM   #6
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In my experience and in my not-so-humble opinion (and this is from K, M and A versions):

The 50/1.4's are the best "all around" 50's - slightly sharper, but they do have more field curvature than the 1.7's, but ultimately they have slightly better bokeh than the 50/1.7's, especially wide open (probably only or mostly due to the 1/2-stop wider aperture).

The 50/1.7's are nearly as sharp as the 50/1.4's, and have a flatter field (maybe important only for macro work with tubes or with a macro-focusing TC).

The 50/2's make nice "fat body caps".

The 55/1.8's (and the optically-slightly-strangled-by-the-Pentax-marketing-department 55/2's) have very nice bokeh, and the "extra" 5 mm of FL does sometimes make a difference.

If I were you (but obviously YMMV), I'd want at least one 50/1.4, at least one 50/1.7, and at least one 55/1.8, and if three 50's were not enough, then "stock up" on the 50/1.4's.
08-29-2015, 07:26 AM   #7
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QuoteOriginally posted by Lenscap Quote
(For the record, I'm not interested in the 1.4 just to say I have one. If it's better, I'm all in, if not, I'll stand pat.)
Optically the A&M50/1.7 & K55/1.8 are pretty close and I like them a bit better than the K50/1.4. If you want a faster lens then get the K50/1.2, that is (and the A50/1.2) are best 50-55mm that Pentax ever made.

If you shoot in low light or in the dark then you will appreciate the faster speed and then there is the bokeh!

Phil.
08-29-2015, 08:04 AM   #8
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Thanks for the input. I have been happy with my 1.7's so far, I just wondered if I didn't know what I was missing.

I have looked at the 1.2's, but the prices on the ones I have seen for sale have kept me from buying one. I suppose an equipment selloff like I'm planning would help fund the purchase.

Gut feeling right now is probably to get a 1.4 and do some comparison work.

And the 1.2 prices don't sound as bad if you say them really fast...

08-29-2015, 09:07 AM   #9
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QuoteOriginally posted by gofour3 Quote
If you want a faster lens then get the K50/1.2, that is (and the A50/1.2) are best 50-55mm that Pentax ever made. If you shoot in low light or in the dark then you will appreciate the faster speed and then there is the bokeh!
Phil just reminded me that, in my earlier reply, I hadn't mentioned any 50/1.2's. [Without a whole lot of thinking (LOL), I merely responded to your original mention of the 50/1.4, 50/1.7, 50/2, and 55/1.8 lenses.]

I have had both of the 50/1.2's (the K for a short while and the A for a longer time), and, as Phil has mentioned, they are beautiful lenses, with beautiful, creamy, dreamy bokeh. However:

1. I personally had a fair amount of trouble focusing with them, so that using them wide open (or close to it) and then hitting the focus within the very shallow field was a hit-or-miss proposition for me. [I would assume that not everyone would experience this.]

2. Some users have found them to seem less sharp than other 50's, but that had not been my experience -- I suspect that at least some of these reports were due to difficulties in focusing (see #1). I found that, when I did happen to nail the focus, the lenses were indeed quite sharp (not wide open, of course).

3. They are not cheap.

So, I'll still basically stick with my suggestion, "If I were you (but obviously YMMV), I'd want at least one 50/1.4, at least one 50/1.7, and at least one 55/1.8, and if three 50's were not enough, then [I'd] 'stock up' on the 50/1.4's".

And ~then~, I suppose, you could always spring for a K 50/1.2 later on down the road -- it would ~really~ be ~home~ on that black K2.

08-29-2015, 09:09 AM   #10
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I was going to suggest the 1.2 as well. Better low light visibility for focusing, even if you don't use 1.2, and it's there if you need it. And I think you'll use it once you have it available. Especially if you get a DSLR with live view and focus peaking, which will be much easier to focus with aging eyes (since you want it to grow old with), and wouldn't result in wasted film for missed shots with the shallow DOF
https://www.pentaxforums.com/forums/122-lens-clubs/74819-post-your-1-2-photos-1-2-only.html
08-29-2015, 10:30 AM   #11
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QuoteOriginally posted by narual Quote
I was going to suggest the 1.2 as well. Better low light visibility for focusing, even if you don't use 1.2, and it's there if you need it. And I think you'll use it once you have it available. Especially if you get a DSLR with live view and focus peaking, which will be much easier to focus with aging eyes (since you want it to grow old with), and wouldn't result in wasted film for missed shots with the shallow DOF
https://www.pentaxforums.com/forums/122-lens-clubs/74819-post-your-1-2-photos-1-2-only.html
Good point - my 50/1.2 experience was back in "Ye Olde Film Days of Yore", and I have only recently (with my K-3) discovered focus peaking in live view. While I have found it quite useful for nailing the focus with long tele lenses, I can see that it would indeed be very useful for focusing an f/1.2.
08-29-2015, 10:41 AM   #12
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Good points about hitting the focus with a 1.2 DOF. My eyes aren't what they used to be, and the combination of dim enough light to require f/1.2 and that crazy-shallow DOF might be an issue. (I have come to really appreciate the little flip-out magnifier on my TLR.)


Edit to add: at the moment, I don't own a DSLR. I'm using film SLRs, and digital P&S for everyday snapshots.
08-29-2015, 12:17 PM   #13
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I've also found the 1.7 a better all around lens than the 1.4. At wide apertures the 1.4 has a more noticible "unsharp zone" about half way to the edges than the 1.7 (on full frame). the center is quite sharp even at 1.4, but if your subject is off center you may think you missed focus slightly. This isn't field curvature, but even best focus in this unsharp zone is a bit soft. I have a few of each lens, and this is quite consistent if you look for it. You can still get great pictures with either lens. I shot the 1.4 for decades without noticing this.
I also have an f1.2, which isn't bad - but I prefer the 1.7.
08-29-2015, 01:28 PM   #14
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I've all the mentioned lenses above besides the 1.2 and IMO there is a big difference between the 1.4 and the 1.7 ones: besides the building quality that for the A 50mm 1.7 is appalling the M50 f1.4 and K50 f1.4 are much better optically speaking than the 1.7, I also prefer the old 55mm f1.8 to the new 50mm f1.7, personally I wouldn't bother having a 50mm f1.7 or f2 at all.
08-29-2015, 02:36 PM   #15
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I agree the build of the SMC-A lenses I've tried is not up to the earlier lenses. The f1.7s I have are SMC-M. My complaints about the 1.4 vs. 1.7 have shone up on FF digital (A7) where trying to focus with mag live view at different points you find the soft areas.
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