[Fat Albert]

I love my 1.7, but I'm wondering if I should upgrade to the A 50 f/1.4 (because I'm insane). Thoughts?

[kiwi_jono]

Well I have both and I love the 1.4 and have not used the 1.7 (which I have had a long time) since I got the 1.4.
The 1.7 is still a great lens but the 1.4 is better. Some people say that they find the 1.7 is sharper stopped down a bit but I have not found that to be the case with mine.
Particularly like the way it performs at f2 (balance of bokeh and sharpness), and sharpness is getting pretty good at f2.8 (see: Gunns Bush - moss carpet | Flickr - Photo Sharing! ).

So for me it was definitely worth the extra price - especially if priced around $150 or less (see: SMC Pentax-A 50mm F1.4 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database )

[SpartanD63]

To be honest, I'd seek out a K55/1.8 if you don't absolutely NEED the A setting. I went from M50/1.7 to the A50/1.7 to the FA50/1.4 then finally to the K55/1.8. I absolutely love this thing. In fact, it's the only 50/55mm lens that I still have.
I ended up selling all of the others at a loss and I have absolutely no regrets.

It's wonderfully sharp, even wide open, but stopping down, as with any lens, leaves things even crispier. The "bokeh" is pretty good, especially as it only has 6 blades, rather than the more modern 8 bladed designs. It can be a bit "choppy" at times, but is very smooth in many situations without harsh contrast in the background. The difference in DOF between 55/1.8 and 50/1.4 at 2m (roughly my most common working distance) is less than a centimeter. (.3cm in fact) So if DOF control is what you're after, the K55/1.8 will do it. And it'll give a FOV more "equivalent" to the 85mm "portrait" standard of 35mm.

The best part? It only costed me $85. (That included the shipping)
Check out the shots taken with it in the K Lens Club thread and see if it'd be worth it to you.

BTW, you're only truly insane if you don't mind stop-down metering or just winging it. But the Takumars and K lenses are well worth the effort.

[DSims]

K-nooow. Not unless you hate the backgrounds of the A50/1.7.

To be honest, I'd seek out a K55/1.8 if you don't absolutely NEED the A setting.

I haven't owned this lens, but this is easy to believe.

[SyncGuy]

The biggest ever joke that i have always heard between the 50/1.7 and 50/1.4 is, the 50/1.7 is sharper wide open than the 50/1.4 is..

I mean, seriously?! I supposed these jokers never knew that the 50/1.4 could be stopped down to f/1.8.. LOL!

Nevertheless, i would say, just go for the 50/1.4! Why? Because it's nice... really.. very, very nice..

Alternatively, like what Spartan recommends, the K55/1.8 if you do not need the A setting..

[MadMathMind]

The biggest ever joke that i have always heard between the 50/1.7 and 50/1.4 is, the 50/1.7 is sharper wide open than the 50/1.4 is..

I mean, seriously?! I supposed these jokers never knew that the 50/1.4 could be stopped down to f/1.8.. LOL!

It's true, but I always interpreted this statement as that 1.4 isn't so good, so the major selling point of the 1.4 over the 1.7 is kinda pointless. The question then becomes how do the two compare at 1.7/1.8? No one ever seems to do that comparison.

I suppose it depends on the actual lens series. The M series f/1.4 goes f/1.4 to f/2.0, so if you want a slight stop down south of f/2, you can't have it. Fortunately, this is not the case on the F series (not sure on the A).

[PPPPPP42]

Bad question to ask, too many people praise what they have and get defensive in general.

Ignore the people suggesting pre A series lenses. If you use the A1.4 on a DSLR and use the rear dial to set aperture you will find there are a ton of intermediate stops you can't get mechanically but the DSLR can do stopping it down automatically, they go:
1.4, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8, 3.2, 3.5, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1, 8.0, 9.0, 10, 11, 13, 14, 16, 18, 20, 22

Since you have an A1.7 my answer would be no, its not worth upgrading to the 1.4, but I always suggest people go for the A50 1.4 if they don't have one already. Its just that much more range to work with before you hit wide open. I would expect the 1.4 will always be sharper at F1.7 (or 1.8) than a max 1.7 lens.

EDIT: Keep an eye out for one cheap, I just saw one local on craigslist with some other Pentax stuff for $50, at that price I woulda bought a second one myself but someone beat me to it.

[jeffshaddix]

I've owned the A50 1.7/1.4/1.2, K55/1.8, and the auto-takumar 55/2.2, as well as many other 3rd party 50mm lenses. I'd recommend keeping the A50/1.7 - the difference is not worth the hassle if you have a lens you like.

As mentioned before, the 55's (both K and takumar) are great, and they do have a different rendering style.

You're not insane to want to get a faster lens - but I'd recommend using the funds for something else.

[SpartanD63]

Bad question to ask, too many people praise what they have and get defensive in general.

Ignore the people suggesting pre A series lenses. If you use the A1.4 on a DSLR and use the rear dial to set aperture you will find there are a ton of intermediate stops you can't get mechanically but the DSLR can do stopping it down automatically, they go:
1.4, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8, 3.2, 3.5, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1, 8.0, 9.0, 10, 11, 13, 14, 16, 18, 20, 22

Yup.
And this is a good point. The pre-A lenses do have limitations. But optically, some of them are worth the hassle IMO. (And yeah, the pre-A lenses can be a major hassle at times) To be honest though, I can't say I've ever missed the extra intermediate stops, but YMMV.

[PPPPPP42]

Its not so much the intermediate stops I use the A series for, its the use of the front and rear dials, the aperture dial is hard to read and access with the beak that Pentax DSLR's have hanging over it, and its totally impossible to use quickly and accurately with gloves wheras I can operate the rear dial to control aperture for an A lens with thick winter gloves on with no need for extra button pressing to make the camera meter correctly. Being able to constantly meter normally to check out parts of a scene (using spot meter mode with a shutter half press) and then make quick adjustments is worth it for me.

[stevebrot]

I mean, seriously?! I supposed these jokers never knew that the 50/1.4 could be stopped down to f/1.8.. LOL!

And the 50/1.7 is sharper wide open than the 50/1.4 at f/1.8 and at f/2.8.

To be truthful, unless you need the wider aperture for DOF purposes, the extra 1/2 stop does not buy you much of anything. OTOH, it might be worth the upgrade just to get the better build of the A 50/1.4.


Steve

---------- Post added 03-10-14 at 10:20 PM ----------

The question then becomes how do the two compare at 1.7/1.8? No one ever seems to do that comparison.

The comparison was done back in the ancient past (about the time I joined this site) in a well-illustrated thread with lots of comparison images. There were also lens reviews from back-in-the-day. It is an open secret that most f/1.4 and f/1.2 lenses are not really superior in any way other than letting more light in and having narrower DOF. I have a couple of f/1.4 lenses that see very little use because their f/1.7, f/1.8, and f/2 brethren are better and smaller and lighter. I will have to find the resource, but back in the 1980s one of the photo magazines (Modern Photography, I think) did a study where they attempted to attain 100 lp/mm resolution with available 35mm films. They used cameras and "fast 50s" from all the major lens makers (Leitz, Canon, Pentax, Nikon, etc.) and NONE (yep none) were faster than f/1.7 and one was f/2 (I will let you guess which one). The f/1.4 lenses were considered to not be up to the task even at moderate apertures.


Steve

[bassek]

A good copy of the A50/1.7 often beats a bad copy of a A50/1.4.

Seb.

[Kerrowdown]

I'm wondering if I should upgrade to the A 50 f/1.4

Perhaps not, but an upgrade to a SMC Pentax-A 50mm F1.2... most certainly.

[Fat Albert]

And the 50/1.7 is sharper wide open than the 50/1.4 at f/1.8 and at f/2.8.

See, this is why I was thinking of upgrading. I figured that the 1.4 would be sharper at f/1.8 because it's not wide open. But if that's not the case, then it doesn't make much sense. Is the build quality of the 1.4 really that much better than the 1.7?

The K 55 f/1.8 looks intriguing, and the price is certainly right. However, I got rid of my M 50 f/1.7 because of the green button issue, so I'm loath to return to such a lens. From what I've been reading, the debates between K/M/A lens quality are quite contentious and I haven't seen a clear consensus regarding which is best.

---------- Post added 03-11-14 at 10:15 AM ----------

Perhaps not, but an upgrade to a SMC Pentax-A 50mm F1.2... most certainly.

See, THIS is the kind of advice I DON'T need. I can't afford a divorce!

[bassek]

From what I've been reading, the debates between K/M/A lens quality are quite contentious and I haven't seen a clear consensus regarding which is best.

Trust me, this will be debated forever! K was the talk like built series, M was compact and A series has the "A"-setting with slightly less high quality build according to some.
I have them all, and like them for different reasons.

Seb