VILTROX - The value option? 

Astro is definitely it's own separate thing, which is why I've started doing these dedicated reviews. Standard lens reviews either don't touch on astro performance at all or do so... sub-optimally? Which is fine, not everyone is set up to test things in every type of condition, and I'm happy to fill the niche.

@@FerventAstronomy Yeah, I'd presume so. However, you and Astro Road have very different opinions on the lens. Would be amazing if you guys could discuss with one another about the lens and your very different test results. Imho, you might have gotten a bad copy. QC on "cheap" chinese lenses usually are not the best. 🤷 Anyway, thanks for the reply and the amazing work you do in testing all lenses.

@@Wistbacka I say this all without meaning to send any shade your way, just in case my tone doesn't come off well in text form: All I did was test the lens, the results are the results. People can download and assess the samples for themselves. Opinions and discussion don't have much of an effect on saggital and tangential astigmatism: what's there is there. My general view on "bad copy" stuff is that it's special pleading. I don't have any emotional (or financial) investment in the lens performing a certain way or not, thus I am free of the pressure to want to believe that it is capable of performing a certain way. If the lens performed "bad" why should one expect that to automatically be an outlier? Viltrox did not supply me a cherry picked review copy as they almost certainly did with other (bigger) reviewers (if they have any business sense). But even if they did I cannot see the results being much different given the physics behind the aberrations. Rather, I bought off-the-shelf just like anyone else. If a company is willing to let extreme "bad copies" into the wild then that's what the end user can expect to get, that type of QC is a low bar. It's unreasonable to have to exchange a lens once, never mind multiple times, hoping to win the lottery and get a "good" copy. I don't know how that became normalized in this industry. At that point there's likely more "bad" copies than "good" ones, and any consumer considering the lens can safely consider it to perform only to the standard of the "bad" copy. The lens is physically well appointed, but inexpensive, and creating optics with well-controlled aberrations for astrophotographic applications is both difficult and expensive. The results match well with the reasonable expectations of the lens' performance set by the realities of capitalism.

My pleasure!

Gah, that sucks! Hopefully things get rectified soon.

Any of the three are good value at their respective price points, and specifically for non-astro use I wouldn’t hesitate to use any of them. Astrophotography is hard-mode for lens performance however. Nothing that I saw when I tested the lens seemed out of the ordinary for it’s price point and optical formula. I don’t think a lot of people really have a grasp on the finer notes of optical engineering that lens aberrations spring from, and the inherent compromises that are necessary in “this” area to achieve something in “that” area. “Decentering” is commonly cited by people when lenses don’t perform up to snuff, but many or most don’t actually know what it is. Which is one of a multitude of potential issues that create various effects. Roger Cicala (the guy who founded LensRentals dot com) wrote a great article a few years back about this very topic if you’re interested. In this case, the astigmatism isn’t something being caused by faults due to copy variation, it’s a result of the lens’ optical formula. The same is true of vignetting. There’s no expectation of mild vignetting given the restrained dimensions of the lens’ front element. That’s one reason why both the Sony and Sigma 14mm lenses have bulbous front elements, and why the Sigma lens is especially huge. And all of that’s fine. Different products for different market segments. There’s always a contingent of people out there who can’t or don’t want to afford the more expensive (top quality) options, and some of these people want to believe the cheap lens is better than the expensive one. When it comes to competing with modern high technology produced by billion-dollar global multinationals however, that’s a tall order. If it could be done as good for so much less they’d be doing it already, it’s a competitive landscape. So I guess as I step off the soap box my testing simply confirms that “you get what you pay for” but even then nothing is perfect!

@@FerventAstronomy Thanks for the great response, it cleared stuff up for sure. I'm going to read the article.

Thanks much, Alan!

Zooms aren’t ideal for astrophotography. Otherwise, any modern higher-end prime will do as good a job as is possible, typically. A wide angle lens with perfectly clean rendering does not exist.

@@FerventAstronomySo I bought a copy of this lens… My copy arrived with faulty AF out of the box and I am returning it for a refund. Not a good first impression of Viltrox.

@@bradl2636 I'm sorry to hear that. I didn't actually test the AF given the application I was concerned with, but it didn't perform well enough optically to justify keeping it personally.

I don't personally think spatial filtering is worth worrying about, especially at normal viewing distances. We aren't taking scientific measurements, we're making art. That said, I'm not sure if the Z8 is free from spatial filtering, as Nikon has a long history of using it in their DSLRs. As for the lens, the tests are conducted in a manner to show off the extent of aberrations. Low magnitude stars, imaged with the highest resolution sensor available, using a tracker to ensure good exposure and zero trailing. If you replicate those conditions and you get better results then I would hang onto the lens and take good care of it.

¯\_(ツ)_/¯ results are results. All I do is test lenses, they perform like they perform. My reviews aren’t about my personal opinion, they’re to give people concrete results so they can make informed buying decisions. I don’t personally see the sense in comparing a fast prime lens to an old, slower zoom lens. Zoom lenses aren’t typically appropriate for astrophotography as they make many optical compromises in order to provide the user with multiple focal lengths in one lens. As for the 14mm GM, I’ve tested that lens as well, you can download the RAW files and compare them yourself to decide which is the right lens for you personally.

Glad it was helpful!

If your budget allows it, the Sigma 14mm f/1.4 or the Sony 14mm f/1.8 are as good optically as is currently available. The Sony is more compact and the Sigma has more quality of life features built in. If your budget doesn't allow it then this Viltrox lens can be an acceptable compromise if you are happy with how it performs. Ultimately that's a personal choice dictated by your desires and circumstances. I'm just here to show you how gear performs for astrophotography, whether you're happy with the performance to cost ratio is completely up to you.

Hi. I'm not quite sure I understand your question, so I will describe the methodology and that should answer any questions. I create two types of testing samples: One set is not tracked, which is to say that these samples are taken with a camera on a stationary tripod. Exposures must be short to prevent star trails. This type of situation is how many will use an ultra-wide lens, but it naturally limits image quality and many of a lens' flaws are hidden or reduced with this type of photo. The second set of samples is done using a star-tracker to track the sky. This allows for much longer exposures as from the camera's perspective the sky does not move. Because of this, image quality of the sky is much higher. There is no motion blur/star trails, there is sufficient exposure, lower ISO may be used if necessary, etc. Since tracked astrophotography solves the problem of motion blur due to the sky's movement it also shows a lens' true optical performance clearly and unambiguously. I hope that helps!

If the price is the same? The Sigma, hands down. Then, once you have it, see if it works for you. It’s wider and performs better optically. But if you then decide that it’s not for you and that you would rather have the Viltrox, sell the Sigma for a profit because it was way under priced and buy the Viltrox. At the same price as the Viltrox I wouldn’t hesitate to get the Sigma regardless of your intention.

@@FerventAstronomy thank you, hopefully i can get the sigma for that price 😊🙏 as i see my tracker (omegon lx3) limit is 3kg so with Sony milc it will be good 🤓thanks again🙏

I returned this lens and got my money back as soon as I was done testing it, so I can't test that bit exactly. That being said, I've been inside tons of lenses and I've never encountered one with any kind of IR source inside, never mind one inside the light path. Not saying it's impossible, but I can't imagine what type of function would be served by that. If I had to guess, it's more likely that your camera has a source inside. If you're using a modified Sony camera, many of their models have IR optocouplers inside the shutter mechanisms so not all models make good modded cameras. Some, like the A7IV, can be used only in some shutter modes and not in others. What brand and model of camera are you using?

@@FerventAstronomy I have a nikon Z6a - but this light bleeding only happens with the Viltrox lens, and only on the Z6 (not my unmodified Z7). I have a sigma 14mm 1.8 as well as a 20mm 1.8 and there is no light bleeding on either the Z6 or the Z7 with those lenses so it must be from something inside the viltrox lens? The pattern in the images is always the same as well, so it can't be an external source or it would look different in different photos

Hmm, that is curious! A side-by-side test would help narrow things down. If you did a dark exposure with the lens cap on, then unlocked the lens and just very slightly rotated it to break the connection to the electrical pins and repeated the exposure. If the image is clean with the connection broken, and if focus stays in the same place after doing that, then it’s a possible hack to still use the lens.

I had a hunch and I went to Kolari Vision for confirmation, and here's what their conversion page for Nikon cameras says: "The D700, D750, D3, D3S, D3X, D4, Z5, Z6, Z7, Z6II, and Z7II contain an internal diagnostic IR Led. This can cause light leaks when using very long exposures and high ISOs in the H-alpha and IR enabled conversions, in the range of 30 second exposures at 6,400 ISO. The D7000, D7100, D600 and D800 also have this monitor but do not have this contamination issue. This issue can be avoided on the Z5, Z6, Z7, Z6II, & Z7II when using silent shutter mode." So there is indeed a IR light source inside the Nikon Z6. It looks like the IR contamination can be avoided using electronic (silent) shutter mode. I'm going to imagine this will limit your max exposure time to 30 seconds, but its possible that there might be a workaround to that. If you do need longer exposures and have to use mechanical shutter, one way that you can also try dealing with this is by using dark frames which are taken during and after your imaging run (put the lens cap on for a few frames, basically), and applying those in your chosen editing program (DSS, PixInsight, Siril, etc) to try and cancel out the IR contamination. If using photoshop you might also try using a dark frame in a layer above your image and setting it's layer blending mode to "subtract". This is most useful if the contamination is the same each time, so the exposure time and ISO value will need to remain the same for the darks as for the regular frames. You might also be able to get away with using LNR (Long exposure Noise Reduction) in-camera, which will automatically take a dark frame and subtract it from the image before outputting the RAW.

@@FerventAstronomy Thanks for taking the time to look into this! I don't think this can be the problem though, because then Id have the same issue with my 20mm 1.8 and 14mm 1.8 wouldn't I? It is only with the viltrox that I get the issue - if the source was the camera then it would show up with any lens I guess?

Happy to help. If you’re doing untracked work with a 12 or 24 megapixel full frame camera I think it’s ok value for money, but the performance is not the best available for astrophotography. It’s worth noting that they best available comparable lenses for astrophotography also have their fair share of optical aberrations such as astigmatism, just less of them or more manageable forms for higher resolution or tracked imaging. The Viltrox, in my mind, is a fine lens if you’re displaying images primarily on social media, for example.

@@FerventAstronomy yeah, that's not me. I'm in the large format printing world. I'm doing tracked imaging on an A7-IV

In your case I would recommend the Sigma 14mm f/1.4, as long as you are ok with doing touch ups on the lower magnitude stars, as stars above a certain brightness threshold will suffer from strong astigmatism

@@FerventAstronomy why not the 14mm GM?

It’s personal preference I suppose, but to elaborate: the Sigma is huge, but for good reason as it controls vignetting, which is more significant with the Sony lens. Which is to say the size of Sigma’s lens isn’t just because of the brighter aperture, but on that front my purposes f/1.4 is preferable to f/1.8. It’s worth noting that I own both and plan to continue to use both.

With F-mount you’re kind of limited to mostly older options, and I’m sure you’re already aware of those. For Z-mount I’d recommend getting a Megadap ETZ21Pro and trying your luck with some of the newer Sigma or Sony lenses. I use one with my Zf and everything I’ve tried works a treat. Your options really open up at that point. All that being said, as you noted no perfect lens exists, but you can get some respectable performance from many newer options.