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10-06-2017, 01:48 PM   #1
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Pentax FA & F lenses...

Hello forum!
Thought I would share my experience with my "new" F and FA lenses....

I bought a couple of F and one FA lens together with an old Pentax SFX camera and some other Pentax gear.

The lenses are:
SMC Pentax-F 24-50mm F4
SMC Pentax-F 35-70mm F3.5-4.5
SMC Pentax-FA 35-80mm F4-5.6

All appearing to be in good condition ( apart from the 35-70mm which has some sort of "tiny smearing" inside the front lens elements)


Prior to buying the package, I read about the lenses in the magnificent reviews here on this forum, and the F lenses did receive quite good reviews. So I had my hopes up when they arrived. In particular for the the F 24-50mm, which just by the touch of it felt like a good quality lens, and the reviews were OK aswell.

The Pentax FA-35-80 on the other hand felt like a toy-lens, all plastic and flimsy handling....so I thought that lens would be the least useful.

So I attached them to my Pentax K-50 and quickly compared them to my DA50mm prime for reference, and just for fun, my DA18-135mm @50mm.
As I mentioned, I had big hopes for the 24-50, and I was a bit baffled when it came out as the softest of the trio, and even more astonished when the "junk" FA 35-80 was the best of them, not far behind my modern lenses IQ wise.

I compared the lenses at 50mm, f5,6, iso100, and 1/20s. Camera on tripod, and 2s delay. I focused on the white sign attached to the fence/barrier, pics are heavily center cropped, but otherwise unedited.

I will perhaps check them more thoroughly later, trough the aperture and fl range, but it seems the 24-50 really is not the best of them....
In particular it lacks contrast...or something...it looks just a bit soft.

Just look at the pics: , the F24-50 @50mm on top, and my DA18-135 @50mm middle and FA35-80 @50mm bottom

Any thoughts?

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PENTAX K-50  Photo 

Last edited by fotofinken; 03-21-2018 at 12:57 AM.
10-06-2017, 02:01 PM   #2
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Before you finalize your conclusions, repeat our tests, but use Live View with focus peaking. I suspect you have fallen victim to front/rear focus errors.
10-06-2017, 02:57 PM   #3
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Live view is definitely the best place to carry out these kinds of tests. That said, pixel peeping on digital can quickly expose flaws in film-era lenses, so it's not surprising that these consumer-ish lenses might turn out the way they did.

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10-06-2017, 05:43 PM   #4
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Contrast is definitely lower on the F 24-50. Shooting at 50 is the extreme of its focal range while the others are in the middle of their ranges. Contrast can alter perception of "sharpness" without influencing resolution.

10-06-2017, 05:47 PM   #5
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Also, if you haven't, do a fine tuning on the focus of each lens.
10-07-2017, 03:07 AM   #6
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Also, bear in mind that f/5.6 is not always "the same" f/5.6, with regard to performance...

On my SMC-M 50/1.7, it's the sharpest aperture, and quite far from wide open.
On my 18-55 WR @18mm, it's sharp enough, and far enough from wide open.
On the same 18-55 @55mm, it's wide open, and it's not quite sharp enough.
On my 55-300 @300mm, it's... less than wide open (minimum is f/5.8) and is definitely soft.

All these lenses can be quite sharp, at a certain aperture which could or could not be f/5.6.
10-07-2017, 05:32 AM   #7
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To my eye, the 24-50mm image is not so much lower in contrast as slightly over exposed relative to the other images (compare the darkness of the foreground grass). I think this has slightly washed out the sign making it a little harder to read.

10-07-2017, 06:47 AM   #8
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QuoteOriginally posted by Pentax Syntax Quote
Contrast is definitely lower on the F 24-50. Shooting at 50 is the extreme of its focal range while the others are in the middle of their ranges. Contrast can alter perception of "sharpness" without influencing resolution.
I agree, to me I would definitely say the second picture which I believe is the 18-135 is the best of the three in overall sharpness of the entire picture. For that lens you are probably in its sweet spot, whereas with the F lens you are at its limit. Based on what I read from others, and what I have or had, I draw two conclusions.
1. I have F28mm f2.8 and FA50mm f1.7. I used to have F 35-70 but sold it. The F series primes are better built (more metal) than FA primes but optically the same. They seem sharp unless you crop them heavily. Very good lenses but they are not quite equals of DA 21, 40 and 70 Limiteds.
2. I have no inclination to go for film era consumer zooms. The ones I had, or had a chance to buy felt flimsy and cheap compared to the current zooms (DA 16-85 and 55-300 PLM) that I have. I would safely expect that the 16-85 and PLM would easily outperform equivalent film era zooms. This post appears to bear that out with the 18-135 giving a better image than the F and FA zooms. True there are variables such as the best aperture and best focal length for each lens to consider but I still think the 18-135 will be better than the film era zooms here.
10-07-2017, 10:41 AM   #9
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Doesn't really surprise me. The DA 18-135mm is quite a fine lens, especially from 18-70mm. I have believed for years that the old FA 35-80mm "cheap" zoom lens for 35mm film bodies has been under-rated, and is really quite good.
10-07-2017, 11:56 AM   #10
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QuoteOriginally posted by jddwoods Quote
I agree, to me I would definitely say the second picture which I believe is the 18-135 is the best of the three in overall sharpness of the entire picture. For that lens you are probably in its sweet spot, whereas with the F lens you are at its limit. Based on what I read from others, and what I have or had, I draw two conclusions.
1. I have F28mm f2.8 and FA50mm f1.7. I used to have F 35-70 but sold it. The F series primes are better built (more metal) than FA primes but optically the same. They seem sharp unless you crop them heavily. Very good lenses but they are not quite equals of DA 21, 40 and 70 Limiteds.
2. I have no inclination to go for film era consumer zooms. The ones I had, or had a chance to buy felt flimsy and cheap compared to the current zooms (DA 16-85 and 55-300 PLM) that I have. I would safely expect that the 16-85 and PLM would easily outperform equivalent film era zooms. This post appears to bear that out with the 18-135 giving a better image than the F and FA zooms. True there are variables such as the best aperture and best focal length for each lens to consider but I still think the 18-135 will be better than the film era zooms here.
I own all three of them... if the FA is the same silver, plasticky version I have.
Despite its build (below average), the image quality impressed me. It performs much better than it looks/feels.

The Pentax-F 35-70 is a great, little lens. If your example is in good conditions, it should be more or less at the level of a 50mm prime at f/8. At central diaphragms it should be fine at all focals.

The 24-50 was considered one of the best consumer zooms of the F series, but if I remember it suffers at the extremes, especially at the tele end, and its sweet spot should be between f/8 and f/9.
To see if it performs the way it should, I'd test it at 35mm f/8, in LiveView.

I have my personal opinion about vintage Pentax AF zooms.
The difference with modern consumer (read: moderately priced) zooms is due to the availability of lens profiles, much more than to a real improvement in optical quality, QC, or build tolerances.
The little Pentax-F 35-70mm was the kit lens of my Sfx-n. Despite its wobbly focusing ring (AF motors were not on par with modern ones) the build quality is definitely better than a modern kit zoom.

Cheers

Paolo

10-07-2017, 12:20 PM   #11
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QuoteOriginally posted by fotofinken Quote
Hello forum!
Thought I would share my experience with my "new" F and FA lenses....

I bought a couple of F and one FA lens together with an old Pentax SFX camera and some other Pentax gear for a small amount.

The lenses are:
SMC Pentax-F 24-50mm F4
SMC Pentax-F 35-70mm F3.5-4.5
SMC Pentax-FA 35-80mm F4-5.6

All appearing to be in good condition ( apart from the 35-70mm which has some sort of "smearing" inside the front lens elements)


Prior to buying the package, I read about the lenses in the magnificent reviews here on this forum, and the F lenses did receive quite good reviews. So I had my hopes up when they arrived. In particular for the the F 24-50mm, which just by the touch of it felt like a good quality lens, and the reviews were OK aswell.

The Pentax FA-35-80 on the other hand felt like a toy-lens, all plastic and flimsy handling....so I thought that lens would be the least useful.

So I attached them to my Pentax K-50 and quickly compared them to my DA50mm prime for reference, and just for fun, my DA18-135mm @50mm.
As I mentioned, I had big hopes for the 24-50, and I was a bit baffled when it came out as the absolute worst of the trio, and even more astonished when the "junk" FA 35-80 was the best of them, not far behind my modern lenses IQ wise.

I compared the lenses at 50mm, f5,6, iso100, and 1/20s. Camera on tripod, and 2s delay. I focused on the white sign attached to the fence/barrier, pics are heavily center cropped, but otherwise unedited.

I will perhaps check them more thoroughly later, trough the aperture and fl range, but it seems the 24-50 really is a bad copy....
In particular it lacks contrast...or something...it looks just really soft.

Just look at the pics: , the F24-50 @50mm on top, and my DA18-135 @50mm middle and FA35-80 @50mm bottom

Any thoughts?
Aha, so it was you who ended up with that one. I considered buying that lot for the 24-50 as the price was really good. Even if just one lens should turn out well you've still made a decent catch.

To me the first image looks out of focus. The suggestions above to use live view are good ones - then you'll avoid any issues with front/back focusing.
10-08-2017, 05:59 AM   #12
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QuoteOriginally posted by cyberjunkie Quote
I own all three of them... if the FA is the same silver, plasticky version I have.
Despite its build (below average), the image quality impressed me. It performs much better than it looks/feels.

The Pentax-F 35-70 is a great, little lens. If your example is in good conditions, it should be more or less at the level of a 50mm prime at f/8. At central diaphragms it should be fine at all focals.

The 24-50 was considered one of the best consumer zooms of the F series, but if I remember it suffers at the extremes, especially at the tele end, and its sweet spot should be between f/8 and f/9.
To see if it performs the way it should, I'd test it at 35mm f/8, in LiveView.

I have my personal opinion about vintage Pentax AF zooms.
The difference with modern consumer (read: moderately priced) zooms is due to the availability of lens profiles, much more than to a real improvement in optical quality, QC, or build tolerances.
The little Pentax-F 35-70mm was the kit lens of my Sfx-n. Despite its wobbly focusing ring (AF motors were not on par with modern ones) the build quality is definitely better than a modern kit zoom.

Cheers

Paolo
You may have a background similar to mine. I bought an SF-10 back around 1987 and with it the F35-70 kit lens, the F28mm and a Sigma 70-210 Ultra Compact. That was my kit. This replaced an old completely manual Minolta SRT 101. When I bought the Pentax autofocus kit I did notice the difference in build quality from the vintage all metal minolta lenses from the early 1970's to the modern (at the time) Pentax lenses. Still the lenses got good usage with the SF-10 for many years despite the wobbly focus and zoom rings on the 35-70 and 70-210 sigma. Fast forward to digital I bought K10D (now my son has it) K-5 and K-3 which are my current bodies. Regarding the Sigma I got rid of it, it was not good on the SF-10 and even worse on digital. I sold the 35-70 more out of my being too critical of build quality than for any other reason. In hindsight, I should have kept it and really evaluated it on my K-5. The F28mm remains a key part on my kit and I used it fairly frequently. Nothing to be critical about the build of this one. It had the same gray exterior as the 35-70 but a solid mostly metal build. I am not looking to replace the 35-70 since I have the DA 16-85 and am very happy with that but I am on the lookout at charity auctions for good vintage F series lenses. I still remember the day when someone a few footsteps ahead of me got an old SF-1n for $15 USD and it had an F50mm f1.4 on it.
10-08-2017, 07:09 AM   #13
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It's not just you, in one of my tests at 35mm, the FA 53-80 image was preferred by 28% of poll respondents.... although only 7% preferred the pixel peeping version. The FA 35-80 is clearly a few people's preferred lens. For the most part, many people who claim to need modern glass, would prefer older glass if they gave it a chance.

My gripe with the FA 35-80 is it feels so flimsy. Maybe I worry about nothing but it feels like it would be easy to break.
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