TEST


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HELP:Camera PENTAX K 20D on tripod. See EXIF. Lens: Samyang 8mm UMC Fish-eye-CSII-F3.5. Found this lens just this morning at an interesting price of 160euros(one year warranty). Second hand. Really good conditions. Just a few piccies at moment of buying inside shop. Seemed good. Really difficult to focus in manual inside that shop. This picture is a test at home. May I have your opinion? I find very difficult to manage manual focusing. Difficult to find right plane of focus. Difficult very difficult with K20D system....but till now I had no troubles with 12-24 Pentax or 18-55 or 55-500 Pentax..I have often used these lenses in manual focusing mode(I prefer). Do I need a special focusing screen? This Samyang seems to be even too soft (image soft I mean)IMHO ;and using it in manual gives me a lot of troubles for focusing (sometimes no red-warn dot-sound signal in central focusing area of my PENTAX viewfinfer...I move focusing ring at right and left but red dot-sound signal gives non signal back inside camera...then suddenly appears. But: is right plane of focus am I looking for? ). In EXIF of this pic you shall read 400mm lens. Crazy. Why? In a different group of piccies I read 0.0 mm. Is this lens in troubles in your opinion? Do you have similar experiences? Can you suggest me a few tips for the right use? and to know if it is really "damaged"? Thank you. PS A few techn tests explain that this lens gives best results back at 5,6-8-11 and low ISO. Can you confirm?
05/08/2020 - 15:59GIULIO57
CategoryGeneral
Shutter Speed1/40
Aperturef/5.6
ISO400
Focal Length400mm
Views/Likes47/1

Toni60

Link Posted 05/08/2020 - 17:12
Large aperture, nice.
Toni

Toni60

Link Posted 05/08/2020 - 20:09
Dear Giulio I just read now your request and I suggest you to contact Samyang.
Regards.
Toni

go4IT

Link Posted 06/08/2020 - 14:54
Good Morning Giulio.
Let me take a few swings at your questions...though I am hardly a lens techie...
The only sharp area in your image is in dead centre---not surprising with a fisheye lens of merely 8mm. I wonder what would happen at f/8 and 11---apertures your literature recommends? Such a small reward (small area in focus at dead centre only--not even reasonably sharp at centre top and centre bottom) for using the supposedly "safe" 5.6 aperture.

I agree with you this lens appears to be quite soft in any case, but would experiment with different subject matter (brick wall test?) before reaching a conclusion on that issue. I must say though that I would never own an 8mm lens---too distorting for my purposes.

As for focusing technique, I too prefer manual, and usually find eye-balling the distance to my main subject, and then moving the distance scale to that distance works best with wide-angle lenses, rather than looking through the viewfinder and turning the focus ring.

It would appear your lens is damaged in that the red-warning, and the EXIF mm reading are both on the fritz. Either that or the lens is just not fully compatible with your camera.

May I suggest you Google your lens to see if anyone else has your problems? If not, I would say sell it as not worth the trouble.
Last Edited by go4IT on 06/08/2020 - 14:55

GIULIO57

Link Posted 06/08/2020 - 15:26
go4IT wrote:
Good Morning Giulio.
Let me take a few swings at your questions...though I am hardly a lens techie...
The only sharp area in your image is in dead centre---not surprising with a fisheye lens of merely 8mm. I wonder what would happen at f/8 and 11---apertures your literature recommends? Such a small reward (small area in focus at dead centre only--not even reasonably sharp at centre top and centre bottom) for using the supposedly "safe" 5.6 aperture.

I agree with you this lens appears to be quite soft in any case, but would experiment with different subject matter (brick wall test?) before reaching a conclusion on that issue. I must say though that I would never own an 8mm lens---too distorting for my purposes.

As for focusing technique, I too prefer manual, and usually find eye-balling the distance to my main subject, and then moving the distance scale to that distance works best with wide-angle lenses, rather than looking through the viewfinder and turning the focus ring.

It would appear your lens is damaged in that the red-warning, and the EXIF mm reading are both on the fritz. Either that or the lens is just not fully compatible with your camera.

May I suggest you Google your lens to see if anyone else has your problems? If not, I would say sell it as not worth the trouble.

Thank you very much.
PPG

Toni60

Link Posted 25/11/2020 - 16:32
Have you solved Giulio?
Toni

GIULIO57

Link Posted 26/12/2020 - 08:18
Toni60 wrote:
Have you solved Giulio?

Yes, I solved it. I wrote to Samyang and they wrote me back a few tips. All features about this lens are normal. Best F numbers are 5.6/8/11. Using my K20 D I got nice results placing it in front of a wall: normal distorsion for a 8mm, great sharpness at 5,6-8 F number, just a few fringe hues at f 11 or f 16. Important to use a tripod when performing such tests. Sorry for my delayed reply ( Mi scuso per il ritardo nella risposta).
PPG
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