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07-12-2021, 09:37 AM   #1
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Help with testing Bower / Samyang 24mm f/1.4 lens

Folks,

I recently obtained the Bower version of the Samyang 24mm f/1.4 lens for use in astrophotography. I am wondering if you can help me with some comparison images I can use to test my copy against while I still have the opportunity to return it if necessary. I am looking for shots of starfields with the sharpest possible stars from a "good" copy of the lens taken from f/1.4 to f/2.0. If you can provide me with RAW files of this from a K-1 or K-1ii, then I can evaluate these against what I am able to obtain from my lens. Can anyone help?

I am hoping for "pixel-sharp" stars at f/2.0 with minimal amounts of coma and astigmatism in the corners from my lens. Is this a reasonable expectation? Any other advice you have about evaluating my copy would be appreciated.

I could also evaluate my copy against what I am able to achieve with my Sigma Art 35mm f/1.4, but I would like to really know what my Bower lens "should" be able to achieve before I decide to keep it.

~ Jon

07-12-2021, 10:10 AM - 1 Like   #2
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Testing? Comparison photos might give a good idea of what might be accomplished, but the lens is only part of that equation. Past experience with Samyang product suggests that the following should be addressed, at minimum.

Test for infinity focus. Tradition with Samyangs wider offerings has been that many lenses leave the factory unable to do fine focus much past 50m or so. Magnified live view should allow you to evaluate out to several hundred meters. I suspect that you will not find a copy of the 24mm that will have been set much further.*

Test for decentering. For this you can use the guide on this site or whatever method our prefer. My first copy of the Rokinon 14/2.8 was decentered.

How to Check Your Lens for Decentering - Articles and Tips | PentaxForums.com

Once the above have been dealt with, the best test for astro might be a few nights in the field.


Steve

* I had to nudge my Rokinon 14/2.8 a fair amount using sketchy DIY instructions found online. It may be easier to have Samyang do the adjustment.
07-12-2021, 10:21 AM   #3
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Used my samyang 24 5 sec ago. Unfortunately I'm near the Arctic circle and its summer time... no night in sight
07-12-2021, 11:18 AM   #4
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QuoteOriginally posted by stevebrot Quote
Testing? Comparison photos might give a good idea of what might be accomplished, but the lens is only part of that equation. Past experience with Samyang product suggests that the following should be addressed, at minimum.

Test for infinity focus. Tradition with Samyangs wider offerings has been that many lenses leave the factory unable to do fine focus much past 50m or so. Magnified live view should allow you to evaluate out to several hundred meters. I suspect that you will not find a copy of the 24mm that will have been set much further.*

Test for decentering. For this you can use the guide on this site or whatever method our prefer. My first copy of the Rokinon 14/2.8 was decentered.

How to Check Your Lens for Decentering - Articles and Tips | PentaxForums.com

Once the above have been dealt with, the best test for astro might be a few nights in the field.


Steve

* I had to nudge my Rokinon 14/2.8 a fair amount using sketchy DIY instructions found online. It may be easier to have Samyang do the adjustment.

Thanks, Steve. This is a method to check for de-centering that I hadn't known about. I had thought a shot of a starfield toward the zenith would make plain any and all important flaws with a copy of the lens. That's what I have planned to do, but was hoping for a comparison image too, to know especially, how much coma and astigmatism should be expected and not considered a "defect".

I am also aware of the infinity focus issue and hope to correct that if I can before further testing.

---------- Post added 07-12-21 at 11:25 AM ----------

QuoteOriginally posted by house Quote
Used my samyang 24 5 sec ago. Unfortunately I'm near the Arctic circle and its summer time... no night in sight
Ha! Thanks, though.

07-12-2021, 11:34 AM   #5
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QuoteOriginally posted by jon.partsch Quote
I could also evaluate my copy against what I am able to achieve with my Sigma Art 35mm f/1.4, but I would like to really know what my Bower lens "should" be able to achieve before I decide to keep it.
The only way you can decide it, is to take an abundance of pictures and see if they satisfy you. And comparing it with the Sigma Art 35mm is comparing the taste of chicken eggs to haddock. If you want to make an honest evaluation you should buy the Samyang version as well and send one of the two (or both) back.
And by the way: we try lenses out and see if we like them, we do not test them, that is language for professional reviewers in some or other magazine.

Last edited by AfterPentax Mark II; 07-12-2021 at 11:39 AM. Reason: typo
07-12-2021, 01:21 PM - 2 Likes   #6
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QuoteOriginally posted by AfterPentax Mark II Quote
The only way you can decide it, is to take an abundance of pictures and see if they satisfy you. And comparing it with the Sigma Art 35mm is comparing the taste of chicken eggs to haddock. If you want to make an honest evaluation you should buy the Samyang version as well and send one of the two (or both) back.
And by the way: we try lenses out and see if we like them, we do not test them, that is language for professional reviewers in some or other magazine.
What is the reason for such condescension and semantic nit-picking? Did you get up on the wrong side of bed today? You should consider whether you have something positive and constructive to say before you post.
07-12-2021, 01:45 PM   #7
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QuoteOriginally posted by AfterPentax Mark II Quote
is comparing the taste of chicken eggs to haddock
With tartar sauce, they both taste the same. Don't ask me how I know...


Steve

07-12-2021, 03:28 PM   #8
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QuoteOriginally posted by jon.partsch Quote
What is the reason for such condescension and semantic nit-picking? Did you get up on the wrong side of bed today? You should consider whether you have something positive and constructive to say before you post.
Sometimes you have ask yourself if your question is reasonable before you post it.
07-12-2021, 04:39 PM   #9
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I'd say that whether you like the lens or whether it fails a test for defects are two different issues. You have to evaluate both of those possibilities.
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