jiggyb21 Posted April 19 Share #1 Posted April 19 Advertisement (gone after registration) Hi everyone. I have a Sigma 20mm DG DN for my Leica SL3 and SL3-s and I have been shooting astro with this lens for years. I have definitely shot many a photo at f/1.4 and never noticed an issue. I decided to run a comprehensive test on all my lenses to see which performed best at certain focal lengths and aperture, just to learn a little more about my equipment. It is expected that the Sigma will sharpen as you close the aperture down but check out these images. There is a very weird haze/glow at the point of focus. I think there is something wrong with the lens because, as I said, I've never noticed this before. The first photo is f/1.4 and f/2.0 (also noticed how dark the 1.4 frame is...almost like it's vignetting the entire frame. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! The second photo is f/2.8 and f/4 (sharpens up a lot obviously) Do I send the lens to Sigma? Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! The second photo is f/2.8 and f/4 (sharpens up a lot obviously) Do I send the lens to Sigma? ' data-webShareUrl='https://www.l-camera-forum.com/topic/420615-sigma-20mm-dg-dn-sudden-issue-at-f14/?do=findComment&comment=5789077'>More sharing options...
Advertisement Posted April 19 Posted April 19 Hi jiggyb21, Take a look here Sigma 20mm DG DN sudden issue at f/1.4. I'm sure you'll find what you were looking for!
jaapv Posted April 19 Share #2 Posted April 19 Focus appears to be on the bucket under the shed. Link to post Share on other sites More sharing options...
jdlaing Posted April 19 Share #3 Posted April 19 Shutter speed is responsible for the dark image. Link to post Share on other sites More sharing options...
jankap Posted April 20 Share #4 Posted April 20 (edited) 10 hours ago, jdlaing said: Shutter speed is responsible for the dark image. 1/3200 at f/1.4 -- 1/1600 at f/2 -- 1/800 at f/2.8 -- 1/400 at f/4 >>🤨 Edited April 20 by jankap Link to post Share on other sites More sharing options...
jiggyb21 Posted April 21 Author Share #5 Posted April 21 Here are four more examples but this time of a flat subject. Manually focused on the brick. Same results. Less obvious, but still darker overall at f/1.4 than the others and notice the halo effect around the wires. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/420615-sigma-20mm-dg-dn-sudden-issue-at-f14/?do=findComment&comment=5789685'>More sharing options...
jankap Posted April 21 Share #6 Posted April 21 (edited) Could you test the lens at infinity? Perhaps this lens has an advantage for astronomy projects. I found this review. Positive results. https://www.cameralabs.com/sigma-20mm-f1-4-dg-dn-art-review/ Edited April 21 by jankap Link to post Share on other sites More sharing options...
jiggyb21 Posted April 28 Author Share #7 Posted April 28 Advertisement (gone after registration) A follow-up for anyone who’s curious or to those who find this thread later. I sent the lens to Sigma and they said the lens was indeed in need of repair. I was quoted $315 for “replacement of fixed barrel 1 unit” From what I understand that is the very front ring that filters screw into and what holds the fixed outermost element in place. That’s all pretty odd to me because I’m pretty careful with my gear but I do go out in all weather conditions. We’ll see. Link to post Share on other sites More sharing options...
jiggyb21 Posted April 28 Author Share #8 Posted April 28 A follow-up for anyone who’s curious or to those who find this thread later. I sent the lens to Sigma and they said the lens was indeed in need of repair. I was quoted $315 for “replacement of fixed barrel 1 unit” From what I understand that is the very front ring that filters screw into and what holds the fixed outermost element in place. That’s all pretty odd to me because I’m pretty careful with my gear but I do go out in all weather conditions. We’ll see. 1 Link to post Share on other sites More sharing options...
Babylonia Posted April 28 Share #9 Posted April 28 Okay. Unfortunately a repair issue for correction. But good to know what could be of importance which parts are sensitive for miss alignment / defect. Link to post Share on other sites More sharing options...
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