[jon.partsch]

Any real difference between these lenses? I want the best, but I can't decide. I care about IQ more than any of the oter features of the lens. That said, if the difference is marginal between a K-mount 50/1.4 for $100 and the FA version for $350, I'd rather save my money and get the cheaper lens.

I would appreciate some advice.

Thanks!

[Blue]

Optically, there isn't much difference. The K is longer and that can give different results more related to a style or appearance. With the M and K, you don't have the A contacts but is still workable and many do it. I have the M version of this lens and the f1.7 that I use on my K film bodies. I have the FA for my digital bodies and MZ-3. The A does allow the use of p-ttl flash and the M and k do not.

[bdery]

If you don't value auto exposure and AF, go with the cheaper, fully manual. Optically they are near enough that it would be about impossible to tell them apart. Coatings are a little different, so the final result might be different also (a LITTLE bit) but none is really better or worse.

I personally used a M 50 f2, a A 50 f1,4, and an F 50 f1,7 (plus a FA 50 macro...). I kept the f because AF is invaluable for me (and the wife), plus I think the f1,7s are slightly better optically than the f1,4s. However, the lens that gave me the most enjoyable "picture taking experience" was the A f1,4. I felt connected to my scene in a way that an AF lens will not give you.

[glasbak]

A little warning about the K version, it can suffer from yellowing.

[Blue]

A little warning about the K version, it can suffer from yellowing.

If that is true, then it must be due to thorium in the coating which would indicate that it is the same as the SMC taks that have that. It is reversible in sunlight.

[Egg Salad]

If the FA 1.4/50 is like my K 1.4/50, I wouldn't go for a f/1.4 at all unless it is cheap to get.
Yes, the K's build quality is just awesome and it has the best focusing feel of all my lenses but the F 1.7/50 is better in almost all respects.
The 1.4 has strong field curvature which makes it pretty unuseable for macros and it isn't as sharp either wide open or better than the 1.7 at smaller apertures. Also my K has a slight colour tint - that well known yellowing - and has more CAs.

I couldn't test it yet but I expect the 1.4 to have the nicer bokeh.
Still if you can get one for 50€/$75 go for it.

FYI. the A and F 1.7/50 are virtually the same lens: I can't find any difference in their pictures although they have different aperture blade designs.

[estudleon]

If the FA 1.4/50 is like my K 1.4/50, I wouldn't go for a f/1.4 at all unless it is cheap to get.
Yes, the K's build quality is just awesome and it has the best focusing feel of all my lenses but the F 1.7/50 is better in almost all respects.
The 1.4 has strong field curvature which makes it pretty unuseable for macros and it isn't as sharp either wide open or better than the 1.7 at smaller apertures. Also my K has a slight colour tint - that well known yellowing - and has more CAs.

I couldn't test it yet but I expect the 1.4 to have the nicer bokeh.
Still if you can get one for 50€/$75 go for it.

FYI. the A and F 1.7/50 are virtually the same lens: I can't find any difference in their pictures although they have different aperture blade designs.

I don't have the K 1,4, but my S-M-C 1,4 (said to be the same as K) hasn't field curvature and very little CA (only in extreme situations).

So, K is not the same than S-M-C ?

Your K copy is under average Ks lenses or my S-M-C copy is above average SMCs lenses?

Or I'm using other lens!!

[rockmaster1964]

I don't have the K 1,4, but my S-M-C 1,4 (said to be the same as K) hasn't field curvature and very little CA (only in extreme situations).

So, K is not the same than S-M-C ?

Your K copy is under average Ks lenses or my S-M-C copy is above average SMCs lenses?

Or I'm using other lens!!

Yours is a K lens. The k lens never actually had a K on them.

[Egg Salad]

As rockmaster wrote, my "K" is the SMC you mentioned.

The CAs aren't very distracting but they are more prominent than on the f/1.7 lenses (only a real problem up to f/2) and the stronger field curvature can be seen claely even in non-macro use.
Oh, and another thing the SMC is noticeably shorter in focal lenght than the 1.7s.

Here's a macro example:
first the "K" 1.4/50 and then the F 1.7/50 - both wide open

[gofour3]

A little warning about the K version, it can suffer from yellowing.

I think you mean the screw mount Takumars suffer from yellowing.

The Pentax SMC “K” series lenses released in 1975, (with bayonet mounts) do not suffer from yellowing. I have over 25 K series lenses, some from 1975 and have never seen or heard of this issue. As far as I know the yellowing issue was fixed with the introduction of the K series lenses.

Phil.

[glasbak]

I think you mean the screw mount Takumars suffer from yellowing.

The Pentax SMC “K” series lenses released in 1975, (with bayonet mounts) do not suffer from yellowing. I have over 25 K series lenses, some from 1975 and have never seen or heard of this issue. As far as I know the yellowing issue was fixed with the introduction of the K series lenses.

Phil.

Indeed, several of my takumars have severe yellowing, and a few weeks treatment with UV light (for erasing eproms) dit not have any effect in curing this.

But my two copies of the K 1:1.4/50 both show also a yellow cast, not as bad (yet) as my takumars though.

And I think that I am also able to compare lenses


George

[monochrome]

A little warning about the K version, it can suffer from yellowing.

If that is true, then it must be due to thorium in the coating which would indicate that it is the same as the SMC taks that have that. It is reversible in sunlight.

Not disputing your contention, but - in nearly 35 years experience with the K50/1.4 I have never seen nor heard of yellowing on the K50/1.4 lens. (SMC PENTAX 1:1.4/50)

I have, however, de-yellowed three 50mm f/1.4 Takumars over the years (two S-M-C and one SMC Takumar), including the one I now own.

[Blue]

Not disputing your contention, but - in nearly 35 years experience with the K50/1.4 I have never seen nor heard of yellowing on the K50/1.4 lens. (SMC PENTAX 1:1.4/50)

I have, however, de-yellowed three 50mm f/1.4 Takumars over the years (two S-M-C and one SMC Takumar), including the one I now own.

I didn't think there were any thorium elements ever used in the K series lenses. However, it may be possible that Asahi had some inventory to use up at the beginning.

Edit: I think some of these guys maybe seeing the actual coatings.

[glasbak]

Not disputing your contention, but - in nearly 35 years experience with the K50/1.4 I have never seen nor heard of yellowing on the K50/1.4 lens. (SMC PENTAX 1:1.4/50)

Looking at your forum name, I can't be supprised

I did not notice it either, but recently I acquired a 'Paterson Optical Test Target 2', and used it to compare various lenses.
From all the 50mm lenses I tested, I noticed a yellow cast in my white target for the K 1:1.4/50. Then I looked throug these lenses at a white surface, and these K 1.4 lenses clearly have a yellow cast.

George

[Blue]

Looking at your forum name, I can't be supprised

I did not notice it either, but recently I acquired a 'Paterson Optical Test Target 2', and used it to compare various lenses.
From all the 50mm lenses I tested, I noticed a yellow cast in my white target for the K 1:1.4/50. Then I looked throug these lenses at a white surface, and these K 1.4 lenses clearly have a yellow cast.

George

Do you have access to a geiger counter?