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08-02-2021, 01:14 PM - 1 Like   #1
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Appalling quality (sample variation) of Samyang 14mm f/2.8 lenses

Folks,

Understanding the highly variable quality (sample variation) of the Samyang/Bower/Rokinon lenses, I recently purchased two copies of the 24mm f/1.4 (a Bower and a Samyang). I was pleased to test them and discover that they both performed very well! Infinity focus was correct, and resolution was great, distortions/aberrations minimal. I sent the Bower back due to slightly higher coma in one corner.

I then purchased 4 copies of the Samyang 14mm f/2.8, and was appalled to discover major flaws with all of them. All four of them didn't focus to infinity. Lend #1 and #2 were off by at least 1/2 inch turn of the focusing ring. I adjusted all of them, which is easy to do with tutorials in various forums and on YouTube. I then took them out to my favorite semi-dark sky location to test them. Aimed at the zenith, Vega was in just about the middle of the frame. I was further frustrated upon opening my raw images in Lightroom to discover additional flaws. Having the constellation Lyra in the center of the frame was great because it also gave me the visual double Epsilon Lyrae to work with along with the super-bright star Vega. I tested all the lenses at f/2.8 and f/1.4.

Lens #1 was astonishingly sharp in the center! Epsilon Lyrae was clearly resolved as two distinct points of light and Vega as a very small round white dot with no color fringing. There was virtually no difference between f/2.8 and f/4.0. Oh, if only performance across the frame was so good!!! I assume one of the elements controlling coma correction was de-centered as the coma distortion was extreme on the left hand side, rendering stars as thin lines pointing toward the center of the image - coma was also terrible here at f/4.0. As I look at the coma distortion all the way around the edges of the image, the lines of light do not point to the center of the image, but to a point about 2/3 of the way across the image in the area of the middle-right side of the image. Coma on the right side of the image was significantly better, and what I would call acceptable.

Lens #2 had about 3/4" of free play in the focusing ring. The action was dampened, but change in focus was not actually engaged until the ring is turned about 3/4". Turn the ring back the other way, and it has to move about 3/4" again for the plane of focus to actually start changing. I thought perhaps I had not tightened the set screws on the focus ring enough when I adjusted the infinity focus point, so I tightened them and tried focusing again the next day, but the free play in the focus was not improved. This lens is not usable.

Lens #3 had optical de-centering - the left side was completely out of focus at both f/2.8 and f/4.0

Lens #4 was the best all-around performer (across the frame), but it was worse in the center than #1 and #3 (#2 couldn't be evaluated due to the play in the focus ring). Vega wasn't as sharp and Epsilon Lyrae was barely resolved as two points of light. In addition, there was hazy color fringing on the left side of stars (not green, magenta, or purple, but instead the expected color of the star e.g. blue for Vega). I don't know what kind of distortion or issue this is, but it was also somewhat evident on lens #3.

Anyway, I am keeping lens #4 for the time being and sending the other three back for replacement, so I will receive three more copies to test. I am hoping to be able to improve upon lens #4.


Last edited by jon.partsch; 08-03-2021 at 08:31 AM.
08-02-2021, 02:08 PM   #2
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Yeah, the infinity is easy to adjust so I didn't worry about that, but it also took 3 or 4 tries for me to get one that wasn't decentered. (I've been told adjusting that also isn't as hard as you might think, but haven't tried it.) Once I got a good one, it is sharp all-around, although I've still only ever used it on APS-C so it could be that the extreme edges aren't as great (or uneven).

Last edited by vonBaloney; 08-02-2021 at 03:45 PM.
08-02-2021, 03:13 PM   #3
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Agree, infinity focus is no big deal to sort (although it shouldn't be as bad as it is - as my copies have been a long way out!).
I'm very happy with my Bower 85 f1.4, and somewhat happy with my Bower 8mm (mainly issues with getting infinity focus right and softness and wide open which I sort of expected).

On the other hand I tried to get a Samyang 14mm for my K-1 and it was badly de-centered (maybe could have used APS-C but useless for FF). Sent back and apparently manufacturer said it was all in spec and any replacement could be the same, which is concerning (retailer gave me my money back anyway). While I would love a FF 14mm prime I don't want to go through all the hassle again (being in New Zealand does not help as we don't generally get this lens, Pentax mount at least, in bricks and mortar stores and have to import).
Its a real pity as it seems like its pretty basic QA issues, that they should be able to sort (even if the price had to go up a bit to ensure they were right).
08-02-2021, 04:58 PM   #4
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QuoteOriginally posted by vonBaloney Quote
Yeah, the infinity is easy to adjust so I didn't worry about that, but it also took 3 or 4 tries for me to get one that wasn't decentered. (I've been told adjusting that also isn't as hard as you might think, but haven't tried it.) Once I got a good one, it is sharp all-around, although I've still only ever used it on APS-C so it could be that the extreme edges aren't as great (or uneven).
If I was at all confident in opening the lens up to correct de-centering, I would have loved to try and correct the issue with lens #1 that I described above. That thing was spectacularly sharp in the center of the frame!

QuoteOriginally posted by kiwi_jono Quote
Agree, infinity focus is no big deal to sort (although it shouldn't be as bad as it is - as my copies have been a long way out!).
I'm very happy with my Bower 85 f1.4, and somewhat happy with my Bower 8mm (mainly issues with getting infinity focus right and softness and wide open which I sort of expected).

On the other hand I tried to get a Samyang 14mm for my K-1 and it was badly de-centered (maybe could have used APS-C but useless for FF). Sent back and apparently manufacturer said it was all in spec and any replacement could be the same, which is concerning (retailer gave me my money back anyway). While I would love a FF 14mm prime I don't want to go through all the hassle again (being in New Zealand does not help as we don't generally get this lens, Pentax mount at least, in bricks and mortar stores and have to import).
Its a real pity as it seems like its pretty basic QA issues, that they should be able to sort (even if the price had to go up a bit to ensure they were right).
I don't do any shooting that would cause me to be tempted to get the 85mm. I am interested in the 135mm f/2.0 however. I am using the 14mm with my K1 mark ii, but I also plan to use it on my K-01 for astrophotography as that one is "full spectrum", and I can add a filter to allow H-alpha and sodium-2 discharge spectrum will blocking most infra-red.

I was almost tempted to keep lens #1 and see if I could send it for warranty service to hopefully correct the extreme coma while retaining the amazing sharpness, but I had read your story or one like it before, and I figured they would just tell me it was already within spec.

Hopefully there will be a winner in the next batch of three lenses that are on the way!

Testing these lenses, I am finding precise focus much more difficult, especially against night sky stars, than with the 24mm f/1.4. Best practice, I think, will be to pre-focus to infinity before the sun goes down, and tape the focus ring in place. That way I can also quickly cycle through the lenses to ensure the stars don't move much between tests. I find it very helpful to have the same stars in the corners of the image for comparison between lenses.

I took shots at ISO 1600 and 4 seconds for the f/2.8 aperture and 8 seconds for the f/4.0 aperture. This ensured very sharp stars even without any tracking.

08-02-2021, 05:34 PM - 2 Likes   #5
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Good on you, Jon, we pay a lot of money for lenses and we're entitled by law to keep sending 'em back until we get one that's up to spec.

Obviously, the companies that sell the cheapest lenses have the worst manufacturing tolerances and do the least amount of quality control checking, but as Lens Rentals will tell you, there are defects and decentreing in any lens of any brand - even Canon L glass.

Since it seems to be a deliberate strategy to make the customer the defacto QC tester, we need to do the brick wall/newspaper thing as soon as we receive our purchase, and keep all the packaging in case we need to box it back up again and mail it off.
08-03-2021, 07:39 AM - 1 Like   #6
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QuoteOriginally posted by clackers Quote
Good on you, Jon, we pay a lot of money for lenses and we're entitled by law to keep sending 'em back until we get one that's up to spec.

Obviously, the companies that sell the cheapest lenses have the worst manufacturing tolerances and do the least amount of quality control checking, but as Lens Rentals will tell you, there are defects and decentreing in any lens of any brand - even Canon L glass.

Since it seems to be a deliberate strategy to make the customer the defacto QC tester, we need to do the brick wall/newspaper thing as soon as we receive our purchase, and keep all the packaging in case we need to box it back up again and mail it off.
Absolutely, even with (and maybe especially with) a $2000 USD new Pentax lens. I have a historic brick building just down the street, and my office building (should I ever return there post-COVID) is a concrete monolith with fluted or grooved patterns in the outside walls - both provide great detailed texture for testing. I am finding shooting the night sky stars to be a great torture test for these wide angle lenses because certain flaws show up with points of light that may not be visible shooting a brick wall.
08-03-2021, 08:39 AM   #7
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I knew these lenses had QC issues, but this really is somewhat amazing. I'm interested in your 3 replacements and how they stack up. I've often thought about the 14mm due to size, but I've held off because I have the Pentax DFA 15-30, and that lens is a solid performer.

08-03-2021, 09:34 AM   #8
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QuoteOriginally posted by clickclick Quote
I knew these lenses had QC issues, but this really is somewhat amazing. I'm interested in your 3 replacements and how they stack up. I've often thought about the 14mm due to size, but I've held off because I have the Pentax DFA 15-30, and that lens is a solid performer.
Yes, well, the Pentax 15-30mm is $1300 USD and the Samyang 14mm is $250 USD or so, so the hassle of obtaining and testing multiple copies is worth it. Plus, I assume a good copy will perform better than the Pentax 15-30mm does at 15mm due to being a prime. I see little utility in a ultra-ride angle zoom. Any ultra-wide shot I am doing will probably be a considered and deliberate set-up, so the convenience of a zoom is probably not needed. Zooms seem much more useful in the middle focal lengths and long focal lengths where you are working with dynamic subjects like human models and wildlife. I had a huge desire to get the Pentax 15-30mm for a while, but I think my 14mm, 24mm and 35mm primes will be even better, and for just slightly less money.
08-03-2021, 11:24 AM - 1 Like   #9
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QuoteOriginally posted by jon.partsch Quote
I then purchased 4 copies of the Samyang 14mm f/2.8, and was appalled to discover major flaws with all of them. All four of them didn't focus to infinity.
Well, that sucks! While the infinity focus problem is not unexpected in a Samyang ultrawide, the other flaws are simply added insult.


QuoteOriginally posted by clackers Quote
Since it seems to be a deliberate strategy to make the customer the
defacto QC tester,
Strangely, while such is fairly rare with higher-end consumer products, it is not unusual in high-end enterprise software (I could name names) where product is often out-of-the-box sketchy, and the service contract de rigueur. As put to me by a VP of a former employer, "For some things we prefer to let our fruit ripen in other people's baskets."


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08-03-2021, 04:20 PM   #10
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QuoteOriginally posted by jon.partsch Quote
Yes, well, the Pentax 15-30mm is $1300 USD and the Samyang 14mm is $250 USD or so, so the hassle of obtaining and testing multiple copies is worth it
I didn't mean you should get a 15-30. Only meant owning one is why I haven't bought the Samyang/Rokinon 14mm. I've looked at the Samyang many times thinking a nice light weight 14mm prime would be nice to have, even though I have the 15-30 already. I'm quite interested in how this works out. I also have a daughter who has a KP and is getting into astro-photography. She has absconded (with my blessings) with my SMC 14, and snagging a Samyang/Rokinon replacement is tempting. Then the question will be be who gets the Samyang - based on the tests here at PF, a good copy is probably better than the SMC 14.
08-03-2021, 05:01 PM - 2 Likes   #11
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QuoteOriginally posted by clickclick Quote
I didn't mean you should get a 15-30. Only meant owning one is why I haven't bought the Samyang/Rokinon 14mm. I've looked at the Samyang many times thinking a nice light weight 14mm prime would be nice to have, even though I have the 15-30 already. I'm quite interested in how this works out. I also have a daughter who has a KP and is getting into astro-photography. She has absconded (with my blessings) with my SMC 14, and snagging a Samyang/Rokinon replacement is tempting. Then the question will be be who gets the Samyang - based on the tests here at PF, a good copy is probably better than the SMC 14.
Sorry, I did not mean to respond as if you were suggesting that I buy the 15-30mm. I was just offering my thoughts on it, since you mentioned it. I think if I wasn't interested in astro, then the 15-30mm would be a logical choice, but as soon as I got and used the Sigma Art 35mm f/1.4, my focus shifted to primes. For me, wide angles below 35mm will be primary used for astrophotography and landscapes, where care is taken to set up the shot carefully, so a zoom isn't necessary, though I'm sure it's a better choice for many.

Oh I also just got the old SMC Pentax-FA J 18-35mm f/4-5.6. It came with a *ist D parts body I purchased. That should be fun for comparison LOL
08-03-2021, 06:41 PM   #12
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QuoteOriginally posted by jon.partsch Quote
Sigma Art 35mm f/1.4, my focus shifted to primes
Sweet lens. Have one sitting next to my keyboard as I type this. Yep, good primes are great.
08-04-2021, 10:17 AM   #13
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Well, replacement lens #1 ... we'll call it lens #5 ... arrived yesterday, and the infinity focus is way off on this one too. Lenses #6 and #7 should arrive tomorrow and night skies should be clear for the next several days for testing.
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