Really interesting and well-made review! Thanks. I also liked the "flapping space bird" very much ;-) Clear skies

@FerventAstronomy

Жыл бұрын

Glad you enjoyed it! Clear skies

Great test. Thank you! Be thankful you can even get that lens for your camera. Canon and Nikon shooters are not so fortunate!

@FerventAstronomy

Жыл бұрын

Thanks my friend! I’m happy to have access to it, although in a pinch I would imagine Nikon Z users can use the Megadap ETZ21 E-mount to Z-mount adapter. Or the TechArt TZE-02, but I haven’t done the research to find out how compatible they are. Had Canon made that flange distance just a little bit shorter the same would be possible with them, although I suspect they limited cross-mount compatibility on purpose. A shame either way.

@alandyer910

Жыл бұрын

@@FerventAstronomy Adapted lenses can be a problem, particularly third party adapters. Even a slight difference in lens to sensor distance as I found some adapters provide versus OEM adapters can make a big difference in off axis aberrations and lens performance. Most photographers won’t notice but we do, on stars, as you showed.

@FerventAstronomy

Жыл бұрын

True enough! Meanwhile, this lens does apparently have tilt adjustments, so I’m sending my copy in to see if they can work out the gremlins. Although the astigmatism on the low-magnitude stars has popped up in samples from all of the 6 copies that I’ve seen. So while I’m hopeful Gentec can balance the frame a bit better I’m thinking it’s unlikely that the astigmatism can be reigned in.

@alandyer910

Жыл бұрын

@@FerventAstronomy While lenses for mirrorless cameras have improved (compare the new Art lens with the original Sigma 20mm from 6 years ago, let alone from lenses 20 years ago) I think when shooting stars with high res cameras we’re expecting more from the optics than what might be possible to deliver in a mass produced lens. There will always been some aberrations and unevenness in the image. I’ve downloaded your Raws from the Sigma and Sony 20mm lenses to look for myself. Interesting to see Sony Raws again, after my ownership of the a7III for a couple of years. Same oddly coloured stars which I think is due to the lack of an anti-alias filter, but the oddly shaped elongated stars might be the spatial filtering in the Sony firmware. The level of chromatic aberration and odd star colouration varies a lot with the Profile chosen - worse with a Camera profile than with an Adobe profile.

@FerventAstronomy

Жыл бұрын

I’m of the same mind, and totally fine with the lens as-is, but if Gentec/Sigma is willing to make it the best lens it can be then the $20 shipping is worth it for sure, haha! Gotta love that 7-year warranty. The nature of the astigmatism on the brightest stars is quite something, though. I’ll have to go back and look at samples from my Sony 20mm, but I don’t remember them having such a unique character. Regarding spatial filtering, I did manage to get the attention of someone who apparently works for Sony a few weeks ago, and they said they’d report up the chain. Not that Sony aren’t aware of the issues, but they’ve been known to listen to feedback from time to time. Perhaps they’ll find a way to spin it as a feature and create a spatial-filtering free “asto” mode. One can dream…. ;)

Thank you so much for the RAW files!

@FerventAstronomy

Жыл бұрын

My pleasure, how else can people decide what’s right for them :)

Hi, which lens would you pick between this one and the Sony 20mm F1.8 with Alpha 7r iii? Thanks for the excellent video! Also, in the second hand market I can find the older Sigma 20mm F1.4, any advice?

@FerventAstronomy

8 ай бұрын

If maximum aperture is more important go with the Sigma. If compact size is more important go with the Sony. Avoid the 20mm f/1.4 DG HSM for DSLRs, it has a lot of optical aberrations.

Thanks for the in-depth review. I really really wanted to like this lens but the awful color fringing on the stars is the deal breaker. I sent mine back, and was considering giving it a second chance when I watched this review to help me decide. I wondered if I'd judged it too harshly, but that LoCA is just so pronounced in your raws as it was in mine with the a1 and adapted to a modified Z7. Yes, it can be processed out, but if you're using it for timelapses, which is a great use for a 20mm 1.4 lens, that's much too time consuming because it also takes the color out of the lagoon nebula and other parts of the milky way. For what it's worth, I think this is the big negative with the Sony 24mm 1.4 GM as well. It's got some coma wide open, but it's also go pronounced purple fringing. Same with the Nikon Z 20mm 1.8. It's bad enough on those lenses that I'd opt for the Sigma 14mm 1.8, the Sony 14mm 1.8 or the 20mm 1.8 which correct it even if the star shape in the corners isn't quite as good.

@FerventAstronomy

Жыл бұрын

My goal is to give people the information they need to decide if any given piece of gear has a place in their bag, so I hope this helped you. Thanks for watching!

Took my new Sony 20mm 1.8 out for its maiden voyage for the March new moon. 20mm is a great focal length for Astro wide field. They all can add filters unlike 14mm and have less distortion. I’ll keep my eyes out for the sigma sales. The better Sigma does the lower Sony will keep their prices.

@FerventAstronomy

Жыл бұрын

Have fun out there!

Love the video, very informative and detailed. When locking the manual focus lock, does the focus stay locked for instance if you need to move between locations and need to take the lens of the camera, crying them separately in the bag?

@FerventAstronomy

9 ай бұрын

I think it might, but I always re-focus due to temperature-induced contraction or expansion that can change the focus on you

@RaymondKPhotoVideography

9 ай бұрын

@@FerventAstronomy Thanks for the reply, Yeah that's some good advise concerning temperature fluctuations influencing the set focus. During a night shoot I might move from location to another, 'short distance', ...so it might not be such a big thing for me. --As long as I always check focus is still okay before shooting at the next location :) But having focus actually lock is really a big thing for me, as the Sony FE 20mm f1.8 G needs to stay on the body (has power) to keep the focus. I really dig how the sigma lens is more geared towards astrophotography. I switch between a couple of lenses quite often during a night, and with the other lenses practically having the option to set/tape the focus point. The Sony is the 'other duck in the pond needing re-focusing. Thanks again for the informative review/test.

@FerventAstronomy

9 ай бұрын

I’m glad you found the video helpful. I could be wrong, but if I recall correctly the Sony lens loses focus when you turn off the camera or unmount the lens but remembers it’s position. When you re attach it or turn the camera back on the camera puts the focusing element back where it was, although I’m not sure if that position is something the camera stores or the lens. Take that with a grain of salt since I don’t have a copy here to test, but I think that’s how I remember it working.

@RaymondKPhotoVideography

9 ай бұрын

@@FerventAstronomy I still have the Sony, (it's been my Astrolens for quite a while) It does indeed remember the focus (camera or lens..) and with the focus switch set to MF, when you turn of the camera it goes back to that focus point. It also does that 'sort of' when you take the lens of and put it back on. Sort of, because it now and then happens that the focus point does reset now and then. Either way, I'm looking forward to see how the Sigma performs, and if it gives me some advantages in the field. Untill tested out, I will keep the Sony... It's still one hack of a great Astro lens!

@FerventAstronomy

9 ай бұрын

I think you’ll really enjoy the Sigma, it’s a good performer, and the feature set makes it very convenient for astro work. The only real gripe I have is the astigmatism on the lowest magnitude stars, but those are usually few and scattered and can easily be cleaned up or replaced in post. Have fun out there!

I never thought as I was a kid that Atari games would be used as a descriptor of high tech, Astrophotography lens defects and characteristics :)))) I still think it is pretty out of the box :)

Did not get the chance to shoot astro yet but did some test shots at night. It is well centered in my copy. Pretty flat field and really sharp at 1.4 at infinity. It is better than my 35mm and 50mm (1.2GM) wide open at infinity wide open sharpness and uniformity. CA I did not notice except some "forced" loca. I will take uniform stars with minimal coma and some correctable color any day of the week compared to larger stars at edges (with wings :) maybe) Also this will have less vignette at common apertures than any other 14mm-15mm or 20mm(1.8s are wide open by then) I'm glad I chose Sigma over Sony 20mm. I pondered over a 24mm GM but I have 35mm GM also and 20mm better suits my kit anyway

@FerventAstronomy

Жыл бұрын

Ultimately I’m sticking with the Sigma for now. Tracked astro shows more of its flaws, but at f/1.4 you don’t need tracking really. For me it really shines as a tool for aurora, where that f/1.4 can be put to good use.

@nat-lj8kt

Жыл бұрын

@@FerventAstronomy in my copy similar astigmatism maybe coma difference in 4 corners but looks acceptable. I used city lights which makes the problem appear more critical because of brightness compared to stars. I'm also using a FE to Z mount af adapter (on Z7 II) which is adding one more possible variable into the mix for tilt or alignment issues. L and FE mounts are lucky to have access to all third party lenses. It is pushing Sony to design better and also be more competitive price wise. Nikon users are stuck with 20mm f1.8 Z which is not good for astro work. Thank you again for the extremely detailed review and yes I agree that for wide angle lenses we need to accept reasonable imperfections at some point which really won't matter for normal people tbh.

I've watched Ian of Lonely Speck do a review of this lens. Probably, you've seen it. It's not as detailed a review as yours by any means. He also got his lens from Sigma directly which makes me wonder whether they double checked the lens and picked out a "good" one. He claims not to see the problems you are illustrating here. It would be very interesting to have you look at his photo's and examine them closely. All of that said, I just tested two new lenses (new to me) with something called MTF mapper software. One was an OM Systems zoom 12-45mm m4/3 lens. The other was the Sony 24-105mm f/4 lens. The OM system lens tested out fantastic. Almost shockingly good. I have an older brother, the Olympus 12-40mm f2.8 pro which I like and thought was plenty sharp and my copy tested well with MTF mapper. Looking at various lab tests online, I thought the new lens could win at f8 and f11. But certainly, the f2.8 model would win at f4. Nope. At every aperture and 3 different focal lengths, the 12-45mm was sharper in the center and the corners. I lucked out big time with this little gem. But for every yin, there has to be a yang...right? The Sony was an absolute dog. It barely matched my kit zoom cheapo Sony 28-70mm at 70mm in the center and was worse in the corners. And I'm not telling you my kit zoom is surprizingly sharp...it's not. Ugly. And my point...which you already know, is lens variation. Sony, Sigma, Olympus...there's substantial variation in what they put out. Not every one of my other Olympus lens are as good as my new little gem...no way. I have the Sigma 12-24mm art lens for Sony e-mount and find it sharp as a tack. Love it. My Sony 200-600mm is also great. But garbage is being put out too. I know...I have a lens I'm sending back.

@FerventAstronomy

Жыл бұрын

I had the Canadian Sigma distributor reach out to Sigma Japan with my sample images, and the engineers at Sigma stated that my lens is performing on spec and as intended.

@evenhandedcommentor6102

Жыл бұрын

@@FerventAstronomy Wow. Maybe the Sony distributor could reach out to Japan and find out the 24-105mm f/4 I have is also on spec. Not good enough for me. I want better than average or nothing.

Then, which one is better for astro? The Sony 1.8 or the Sigma 1.4?

@FerventAstronomy

Жыл бұрын

That’s not quite cut and dry, and I’ll be releasing a comprehensive comparison when I can get the chance to film it, but for my work in need the extra speed so I went with the sigma

You holding out on us with Fervent shirts?

@FerventAstronomy

Жыл бұрын

Nope, I'm just terrible at self-promotion. You can find everything from shirts to shower curtains over on Fervent's RedBubble: FerventAstro.redbubble.com

You've been unlucky with the copies you've received here. I downloaded some samples from an Instagram contact and couldn't believe how good it was, corner to corner, so I bought one myself. My first copy had a weak corner, but when focusing towards that corner, all corners were far better than your copy here. Despite being able to help the poor corner by focusing towards it (good practice for astro anyway, rather than focusing on the centre), the retailer did want to replace it. The 2nd copy is better and exhibits round stars corner to corner except for extremely bright stars. Comparing directly with a couple of 24mm GM lenses, this Sigma beats it in pretty much every regard in terms of IQ (unless someone specifically wants the 24mm field of view of course). Happy to provide sample files if you're interested.

@FerventAstronomy

Жыл бұрын

Well, as you can see, very bright stars do indeed show severe astigmatism. Capella (+0.7 magnitude), Vega (+0.2), and to a lesser extent Menkalinan (+1.89) all show quite bad astigmatism. I don’t doubt that a better copy might exist, but this is what Sigma is letting out the door, so this is what people can expect to get from what I’ve experienced. I don’t know how to assess someone else’s opinion that I just have bad luck, especially when that same person had to take back their fist copy as well. Every copy I’ve seen samples from, including from one of Sigma’s own ambassadors, exhibits the same reproduction when faced with stars brighter than +2.0 visual magnitude. But that doesn’t really bother me, as it’s a small number of stars all things considered. The uneven rendition across the frame is a bigger issue I feel, and one which I am exploring sending the lens in for a warranty repair over. I also noticed after recording the video that the vignetting is not symmetrically centred. Until and unless I get a better copy in my hands, my experience remains my experience. But if Sigma is going to market a lens for Astro, then they really need to make sure their quality control is extra on point. If this is a “bad copy” then no copy this bad should have ever made it out to consumers, never mind the worse copy I received first.

@timwhite1111

Жыл бұрын

@@FerventAstronomy yes definitely agree regarding quality control, I've seen more people sending these back than I have accepting them, which isn't very reassuring. Another interesting thing with this Sigma is that the flat field nature of it is more forgiving/tolerant of astromodified bodies than I've seen with any other wide angle lenses so far, with good corners at f1.4 (I need to stop down to f2.8 with my 24mm GM on a modded body, and it's still far from ideal).

@timwhite1111

Жыл бұрын

@@FerventAstronomy couple of sample pics from mine available here if you choose to have a look, entirely up to you. A1 with Sigma 20mm DG DN at f1.4 and f2. drive.google.com/drive/folders/1BhPtBhsQESEPqfXEnGO0Hxel90m4qeM8?usp=sharing

@FerventAstronomy

Жыл бұрын

@Tim White Hi Tim, I took a look at the samples you sent over. I’m assuming they’re untracked, given that they’re 8 seconds at ISO 1600 with some elongation at the top and bottom of the frame. Let me know if this is not the case. In news that’s somewhat reassuring to me but that might be a bit unsettling to you, it appears that your copy has almost identical reproduction to mine. Since you didn’t put any really low magnitude stars in the corner you wouldn’t notice the same level of astigmatism in these particular samples. As well, the noise from the high ISO used and the low exposure level mask the subtle astigmatism on dimmer stars that would be more apparent in a long tracked exposure at a low ISO. That said, the brightest stars that at the edge of the frame exhibit the same aggressive astigmatism that’s shown up in every copy I’ve seen. If you look left of the Andromeda galaxy to the square in Pegasus, you’ll notice two brighter stars near the edge. The upper star Algenib (+2.82) and the lower star Markab (+2.49) both experience pronounced astigmatism in both axes, as well as the same strong chromatic aberration. Had Capella been at the edge I’m sure it would be even more obvious. Not to say that there’s anything “wrong” here. I think this is an inherent characteristic of this lens (wide angle designs are hard). As I said at some point in my rather too-long review, the flat field is a welcome trade off for the cost of a few stars spreading their wings.

@timwhite1111

Жыл бұрын

@@FerventAstronomy it was tracked despite the short exposure (was just testing between clouds). All corner stars even faint ones looked poor on yours, extending quite far into the frame from the edges, that's not the case on mine with short exposures or long exposures of a couple mins. I did put M45 in a corner and it was still pretty impressive, moreso than any other wide angle I've tried so far. As for CA, this Sigma CA at f1.4 is still less severe than Sony 24 GM stopped down to f2. I was considering buying 2 but the increasing number of reports of dodgy ones is a put off, this shouldn't be this much of a lottery.