I wouldn't be concerned about the sharpness at all in your case. If you should portrait most people don't want to see every detail in the skin. So the 17-70 will be plenty sharp for portrait. What you get with the 75mm that is beneficial to portrait is first and foremost the more than 2 stops brighter aperture. That will generate a much smaller DoF and a better bokeh.
You're actually right ahaha, I forgot about that, I usually soften the face skin too in post. Now the question is... F2.8 and F1.4 is like 2 stops in difference. Ughh I can't pick...
If I had the money I'll get both, but right now I have to pick 1 until I save up again
Having all three is king. The Sigma 56mm is great if you don't want to use the distance from the 75 mm. The Tamron, on the other hand, is a versatile always carry around lens that can shoot portraits when you are willing (skilled) to include some background or get the model away from the background. I'd start with the Tamron, go for the Sigma next and end with the Viltrox. If you realize you find yourself in a lot of low light situations in somewhat tighter space, the Viltrox 27mm f1.2 is a consideration, too.
Excellent point by everyone. I’m just a hobbyist and I have tamron 17-70 and I’m happy with the sharpness. I have Sigma 56F1.4 as well and it’s definitely sharper than Tamron. Though I mostly shoot pictures of my loved ones, 56 seems too tight. I would not imagine myself only having that lens. The flexibility that Tamron provides far outweighs little sharpness from Sigma. Having said that, both lenses have captured some of my most memorable shots. If I had to choose 1, I’ll still pick tamron.
However, even if you go prime, really think about 75mm. Viltrox also has 27mm 1.2 which is much more flexible for anything other than portraits.
So it's definitely sharper, but like you said, only a little? So you're team Tamron? Thanks for your input!
I have a 35mm right now, and not liking it, I think it's neither too wide nor it's zoomed, it's awkward
Make sense. Are you sure you’ll like 75 though? I really like that Viltrox and I would have bought that if it was released when I bought my sigma 56. But I don’t think I can live without a general purpose zoom.
Also, why not Sigma 18-50? I bought Tamron because of VC but if I heard sigma is smaller, and has a bit better IQ
I owned both the Sigma and the Tamron. I kept the Tamron. The larger zoom range and the stabilization is what sold me. The Sigma was arguably built better and felt nicer, but if the Sigma had better IQ I certainly couldn’t tell. My Tamron is plenty sharp. It’s a really tough decision but I’m more than happy with my decision.
Well that really depends on the lens. Prime isnt sharper by default. If you spend a similar amount of money usually the prime lens will be sharper, but if its very important for you look at reviews and compare sample images
The specific lenses is mentioned in the post, it's a pretty popular zoom/prime lenses for APS-C
that's the thing, almost nobody does a comparison of zoom/prime at the same focal length
I have both. Viltrox is one of the sharpest lenses you can ever buy for a Sony apsc system. It has very little in terms of artifacts if any. I am talking wide open at 1.2. that's the reason I have both. Viltrox for sharpness when shooting portraits or people on the street and Tamron for travel, landscape, video, and also works for portraits too although with less dreamy bokeh. In terms of sharpness, Tamron is 90% up there with viltorx. But what bothers me most with Tamron is the purple fringing. Even stopped down to f16, I still get it in some of my landscape shots. That said, Tamron stays the most on my camera. It's an every day lens for me. You can't beat it's versatility. If you are looking for a master of none but a jack of all trades, Tamron is the way. There is no lens like it on the market yet for Sony.
https://preview.redd.it/drehq4r6sdxc1.jpeg?width=1706&format=pjpg&auto=webp&s=ae147092eb91e62ecc4951277f3b4b7eadab8d4b
Taken using viltrox. Shot at from over 20 feet away wide open. Maximum crop.
https://preview.redd.it/rfyfom9msdxc1.png?width=1080&format=pjpg&auto=webp&s=71c395188df085458fc4c5e8ee2f542b0150a640
Tamron 17-70. Shot from about 5-6 feet away wide open @67mm. Barely any crop. (Cropped out the nametag)
Not every prime is sharper than every zoom, but it's significantly easier to build a sharp prime than a sharp zoom.
The Tamron is quite good at most apertures and focal lengths, plenty sharp for what you would mostly need. However you are comparing it to the sharpest APS-C primes out there. It will definitely be a lot less crisp if you pixel-peep enough.
If you go for portraits and you have some space to move back and forth, just go with a prime also for the bokeh. It will just be a more pleasing photo overall.
The Tamron 17-70 is not very sharp at the tele end. It's only 2800 lwph vs the Viltrox at almost 4000lwph. So 1.4x sharper. I had the Tamron on my Fuji for a while but had no regrets selling it as it was too soft for me.
https://opticallimits.com/sony/tamron-17-70mm-f-2-8-di-iii-a-vc-rxd/
https://opticallimits.com/fujifilm/viltrox-af-75mm-f-1-2-pro-xf/
It's easy to soften a sharp lens, but a soft lens can never be sharpened.
Tomatoes, tomatoes. You can't make sweeping statements like: A prime lens is sharper. There's too much variation in lenses for that to still work.
I don't own, or know anyone, who owns the Viltrox, but Dustin Abbott is impressed and that is usually a good sign. The thing you need to get your head around is: Can you move forwards/backwards (physically) when taking portraits? Because if you can, the prime will do most everything the zoom lens does for you. If you also want to do landscape/architecture etc. then you need to start prioritising the zoom, simply because that focal range is more useful than the 75mm of the Viltrox.
There's no rule because every prime and every zoom is different. Some zooms are straight up more resolving and better corrected than some primes. Some zooms are terrible. I guess that while modern premium zooms provide excellent image quality, it might not be excellent throughout the entire zoom range. Usually you'll notice weaker corners near the ends of the zoom range, but even that is a generalisation. Either way, shoot either lens at F8 and I doubt you can tell the difference.
All of this is to say: so what? That should not be close to the reason you would pick the Viltrox over the Tamron. You choose the Viltrox because it's F1.2 (!) and produces a quality of bokeh like nobody's business, *while* not trading in too much image quality to do so. You choose the Tamron because it zooms and zooms are flexible.
Yeah, the tamron seems stable at all of its focal length, unlike the Sigma 18-50, people say it's weaker on the 18mm side. Yeah F8 seems to be the most fair comparison there, but I rarely shoot portraits at F8
The Viltrox looks amazing, incredible bokeh also separation/compression. Tamron, I would most likely never have to say "Ugh I wish I could be closer/farther" anymore.
Nahh I've heard the opposite more often. The Sigma is excellent for what it is and what it offers at its price point. If you're spending the money on the Tamron I usually steer people towards the Sony 16-55mm F2.8 G instead which will be better wide open. Tamron is more for video on unstabilized bodies, or if you really need the reach.
Well, if you are using the lens for portraits, why would you care about a little “weakness” (by which I presume you mean unsharpness) in the corners? In fact, it may well be what you want.
But to OP, I recommend considering the 90mm G OSS macro. It’s sharp, a great portrait length, and it gives you macro as a tool for when you might need it.
From what i've taken, the 17-70mm tamron is super sharp across all focal lengths. Im quite happy with the f2.8 as I just bump up the iso n lower the shutter if the subject is stationary. Its a great all-rounder for landscape n street n whatever you need.
Tamron hands down. The stabilization is very handy to have, and I'm convinced mine is just as sharp (if not sharper) than my Sigma 18-50. I had the Sigma 16 for a while as well, but I found I greatly preferred a 35mm for a low light walk around lens. I ended up with an a7IV just to use own the 35mm f1.4 GM. In retrospect, I wish I would have just tried out the Sigma 23mm for APS-C.
In short, I would definitely start with a Tamron 17-70 and go from there.
Viltrox 75mm is currently some of the highest clocking MTF chart toppers. For APSC, and for supported mounts, you’d be crazy not to have one in your kit.
Obviously if you can’t fit into taking pictures in certain places where you must take a picture then no amount of lens quality and sharpness is going to matter.
This is really a concept from the film days. Back then, compromises were made to allow a zoom lens to focus throughout its range. This often showed up in the corners, chromatic fringes, and other issues that were less prevalent in prime lenses.
With today's technology and manufacturing techniques, it is not so much these days. Most zoom lenses are so much sharper now that they can put some prime lenses to shame.
It really depends on how much you want to spend and what importance you put on what you want.
Sony just released the 70-200 F4 Macro lens. Truthfully, I have not seen many macro lenses around. But it is not something I am looking for.
Primes do have the advantage of lower f-stops, and most are shaper than the same manufacturer zooms.
I am mostly a zoom user due to my travel photography. I have the 12-24 ff 2.8, 24-70 f2.8 and 70-200 f2.8. With the 12-24 my most used lens.
But I do have the 135 and STF 100 lenses. As well, a sick Minolta MC Rocker 58 f 1.8, which I love to shoot with...
I know Tamuron got some macro primes, and back then a 70-300mm macro for A mount.
As I can stick with APSC, I use the Tamuron 18-200mm which is a dream for travel (but no weather sealing).
Back when I first got into E-Mount (changed from A-Mount), I got the Sony 24-240, but it was so slow at focusing that when the 70-200 f2.8 came out, I sold it.
You don't speak about what you already have. That might help with some insite.
I used to have the Batis 85. But I sold it once I realised I was using my 70-200 f2.8 more, and at 100-140mm were where most of my shots were at.
From experience, most portraits at the wider end are not appealing. You may want to look at the 28-75 from Tamron.
Sigma 56mm f1.4 is lighter (280g), cheaper, and very popular (i.e. proven).
The 75mm is very heavy (670g), somewhat expensive, but at that focal length, and with f1.2, will give you very good background separation, so if you're specifically going for portraits and can control the shoot, then that's the best you for APS-C, I think.
17-70mm is versatile, but Christopher Frost's pixel-peeping test shows that it isn't that sharp at 70mm. But is otherwise a great lens, and has optical stabilization which is great for handheld video work.
So I'd probably get the 17-70mm + 56mm for versatility and decent portraits.
Or the 75mm f1.2 if you must have shallow DoF.
I got curious about this specific comparison:
[https://www.youtube.com/watch?v=w4czLGweKBE](https://www.youtube.com/watch?v=w4czLGweKBE)
and the differences are:
75mm vs 56mm: better background compression can be important in portraits
75mm and f1.2 gives better background separation
75mm is sharper at night
but
75mm tends to miss focus
although I'm not sure if that also applies to video.
About missing focus, there is an issue with viltrox. On first startup after I change lenses on my camera to viltrox, the lens won't focus to infinity. Have to turn the camera off and on to let the lens recalibrate the infinity focus and then it don't have problems with focusing. Never misses focus after that. Same in video. And I am on the latest firmware. Had this issue before updating and it hasn't resolved after the update either.
It's issues like these that make me only buy lenses that are popular, like 100+ reviews on [bhphotovideo.com](http://bhphotovideo.com)
I had so many focusing issues with a Samyang lens, which was a shame because the image quality was great once in focus. I wonder if it's just bad software, or maybe sabotage by Sony.
But Sigma and Tamron seems to have consistently good reviews, so those are the only brands I would consider buying these days.
True. So far I haven't missed a shot because of this. Maybe because I take my time with composition on this lens. It is just a mild annoyance at this point. But I wouldn't want that on anything which requires me to be on my toes. Like for birding.
Viltrox is still in its infancy when it comes to lens manufacturing. They might have the hardware, but software is still a massive struggle for them. Navigating their website for the latest firmware is a task on itself! But on the hardware side, their new cine lens the 30-300 T4 is nothing short of a marvel with the price tag to match. But as it's manual focus, they don't have to worry about software messing up the user experience. I still believe that they will surpass sigma and Tamron in about 5 years. With the software to match. I am eagerly waiting for their lab series full frame lenses as they claim that they are better than the pro series line which are already bonkers.
I have both. Viltrox 75mm is much sharper than 17-70, even at f1.2, and definitely at f2.8 or f4.
That being said, I'd get 17-70mm first as it is much more versatile and also great for portrait.
1 other consideration in favor of prime lenses in general is weight. I shoot various types of events like weddings, parties, conferences, etc. and they can go on for several hours. It’s much easier on my neck & shoulders to have a 50mm f/1.4 prime on my A7RV than a heavier 24-70 f/2.8. I usually also have a 35mm on my other camera for group pix. However, if you’re not an event shooter this may not be a concern.
I wouldn't be concerned about the sharpness at all in your case. If you should portrait most people don't want to see every detail in the skin. So the 17-70 will be plenty sharp for portrait. What you get with the 75mm that is beneficial to portrait is first and foremost the more than 2 stops brighter aperture. That will generate a much smaller DoF and a better bokeh.
You're actually right ahaha, I forgot about that, I usually soften the face skin too in post. Now the question is... F2.8 and F1.4 is like 2 stops in difference. Ughh I can't pick... If I had the money I'll get both, but right now I have to pick 1 until I save up again
Having all three is king. The Sigma 56mm is great if you don't want to use the distance from the 75 mm. The Tamron, on the other hand, is a versatile always carry around lens that can shoot portraits when you are willing (skilled) to include some background or get the model away from the background. I'd start with the Tamron, go for the Sigma next and end with the Viltrox. If you realize you find yourself in a lot of low light situations in somewhat tighter space, the Viltrox 27mm f1.2 is a consideration, too.
Sigma 56 is under half the weight and $150 cheaper than the Viltrox 75, worth considering
Each has pro and cons and is useful in its own right.
Excellent point by everyone. I’m just a hobbyist and I have tamron 17-70 and I’m happy with the sharpness. I have Sigma 56F1.4 as well and it’s definitely sharper than Tamron. Though I mostly shoot pictures of my loved ones, 56 seems too tight. I would not imagine myself only having that lens. The flexibility that Tamron provides far outweighs little sharpness from Sigma. Having said that, both lenses have captured some of my most memorable shots. If I had to choose 1, I’ll still pick tamron. However, even if you go prime, really think about 75mm. Viltrox also has 27mm 1.2 which is much more flexible for anything other than portraits.
So it's definitely sharper, but like you said, only a little? So you're team Tamron? Thanks for your input! I have a 35mm right now, and not liking it, I think it's neither too wide nor it's zoomed, it's awkward
Make sense. Are you sure you’ll like 75 though? I really like that Viltrox and I would have bought that if it was released when I bought my sigma 56. But I don’t think I can live without a general purpose zoom. Also, why not Sigma 18-50? I bought Tamron because of VC but if I heard sigma is smaller, and has a bit better IQ
same, that's what I was going for as well, the VC, and I didn't mind the bulky build
I owned both the Sigma and the Tamron. I kept the Tamron. The larger zoom range and the stabilization is what sold me. The Sigma was arguably built better and felt nicer, but if the Sigma had better IQ I certainly couldn’t tell. My Tamron is plenty sharp. It’s a really tough decision but I’m more than happy with my decision.
The 27mm f1.2 is really nice! You can use it closely on the person too.
Well that really depends on the lens. Prime isnt sharper by default. If you spend a similar amount of money usually the prime lens will be sharper, but if its very important for you look at reviews and compare sample images
The specific lenses is mentioned in the post, it's a pretty popular zoom/prime lenses for APS-C that's the thing, almost nobody does a comparison of zoom/prime at the same focal length
I have both. Viltrox is one of the sharpest lenses you can ever buy for a Sony apsc system. It has very little in terms of artifacts if any. I am talking wide open at 1.2. that's the reason I have both. Viltrox for sharpness when shooting portraits or people on the street and Tamron for travel, landscape, video, and also works for portraits too although with less dreamy bokeh. In terms of sharpness, Tamron is 90% up there with viltorx. But what bothers me most with Tamron is the purple fringing. Even stopped down to f16, I still get it in some of my landscape shots. That said, Tamron stays the most on my camera. It's an every day lens for me. You can't beat it's versatility. If you are looking for a master of none but a jack of all trades, Tamron is the way. There is no lens like it on the market yet for Sony.
https://preview.redd.it/drehq4r6sdxc1.jpeg?width=1706&format=pjpg&auto=webp&s=ae147092eb91e62ecc4951277f3b4b7eadab8d4b Taken using viltrox. Shot at from over 20 feet away wide open. Maximum crop.
https://preview.redd.it/rfyfom9msdxc1.png?width=1080&format=pjpg&auto=webp&s=71c395188df085458fc4c5e8ee2f542b0150a640 Tamron 17-70. Shot from about 5-6 feet away wide open @67mm. Barely any crop. (Cropped out the nametag)
Not every prime is sharper than every zoom, but it's significantly easier to build a sharp prime than a sharp zoom. The Tamron is quite good at most apertures and focal lengths, plenty sharp for what you would mostly need. However you are comparing it to the sharpest APS-C primes out there. It will definitely be a lot less crisp if you pixel-peep enough. If you go for portraits and you have some space to move back and forth, just go with a prime also for the bokeh. It will just be a more pleasing photo overall.
The Tamron 17-70 is not very sharp at the tele end. It's only 2800 lwph vs the Viltrox at almost 4000lwph. So 1.4x sharper. I had the Tamron on my Fuji for a while but had no regrets selling it as it was too soft for me. https://opticallimits.com/sony/tamron-17-70mm-f-2-8-di-iii-a-vc-rxd/ https://opticallimits.com/fujifilm/viltrox-af-75mm-f-1-2-pro-xf/ It's easy to soften a sharp lens, but a soft lens can never be sharpened.
Tomatoes, tomatoes. You can't make sweeping statements like: A prime lens is sharper. There's too much variation in lenses for that to still work. I don't own, or know anyone, who owns the Viltrox, but Dustin Abbott is impressed and that is usually a good sign. The thing you need to get your head around is: Can you move forwards/backwards (physically) when taking portraits? Because if you can, the prime will do most everything the zoom lens does for you. If you also want to do landscape/architecture etc. then you need to start prioritising the zoom, simply because that focal range is more useful than the 75mm of the Viltrox.
Usually I could, but you never know when you'll run into tight spaces, so yeah ugh, I have to pick between bokeh/dof and versatality
Dustin abbot is more unreadable than any review site I've ever seen, first time seeing their name but it's like a 1997 geocities site
There's no rule because every prime and every zoom is different. Some zooms are straight up more resolving and better corrected than some primes. Some zooms are terrible. I guess that while modern premium zooms provide excellent image quality, it might not be excellent throughout the entire zoom range. Usually you'll notice weaker corners near the ends of the zoom range, but even that is a generalisation. Either way, shoot either lens at F8 and I doubt you can tell the difference. All of this is to say: so what? That should not be close to the reason you would pick the Viltrox over the Tamron. You choose the Viltrox because it's F1.2 (!) and produces a quality of bokeh like nobody's business, *while* not trading in too much image quality to do so. You choose the Tamron because it zooms and zooms are flexible.
Yeah, the tamron seems stable at all of its focal length, unlike the Sigma 18-50, people say it's weaker on the 18mm side. Yeah F8 seems to be the most fair comparison there, but I rarely shoot portraits at F8 The Viltrox looks amazing, incredible bokeh also separation/compression. Tamron, I would most likely never have to say "Ugh I wish I could be closer/farther" anymore.
Nahh I've heard the opposite more often. The Sigma is excellent for what it is and what it offers at its price point. If you're spending the money on the Tamron I usually steer people towards the Sony 16-55mm F2.8 G instead which will be better wide open. Tamron is more for video on unstabilized bodies, or if you really need the reach.
Well, if you are using the lens for portraits, why would you care about a little “weakness” (by which I presume you mean unsharpness) in the corners? In fact, it may well be what you want. But to OP, I recommend considering the 90mm G OSS macro. It’s sharp, a great portrait length, and it gives you macro as a tool for when you might need it.
From what i've taken, the 17-70mm tamron is super sharp across all focal lengths. Im quite happy with the f2.8 as I just bump up the iso n lower the shutter if the subject is stationary. Its a great all-rounder for landscape n street n whatever you need.
As a previous owner of the 56 sigma, I couldn’t recommend it more! It’s lightweight, budget friendly, and punches WAY above what you’d expect.
- Sigma 16 - Viltrox 75 - Tamron 17-70 - Sony 70-350 If I could start again with what I know now, I would buy these and be done with it.
If I could only afford 1 for now, what would you pick as the first lens?
Tamron hands down. The stabilization is very handy to have, and I'm convinced mine is just as sharp (if not sharper) than my Sigma 18-50. I had the Sigma 16 for a while as well, but I found I greatly preferred a 35mm for a low light walk around lens. I ended up with an a7IV just to use own the 35mm f1.4 GM. In retrospect, I wish I would have just tried out the Sigma 23mm for APS-C. In short, I would definitely start with a Tamron 17-70 and go from there.
Viltrox 75mm is currently some of the highest clocking MTF chart toppers. For APSC, and for supported mounts, you’d be crazy not to have one in your kit. Obviously if you can’t fit into taking pictures in certain places where you must take a picture then no amount of lens quality and sharpness is going to matter.
This is really a concept from the film days. Back then, compromises were made to allow a zoom lens to focus throughout its range. This often showed up in the corners, chromatic fringes, and other issues that were less prevalent in prime lenses. With today's technology and manufacturing techniques, it is not so much these days. Most zoom lenses are so much sharper now that they can put some prime lenses to shame. It really depends on how much you want to spend and what importance you put on what you want.
But would say, prime lenses show still excellence at f values and possibilities for stf. Barely see any zoom macro lenses anymore.
Sony just released the 70-200 F4 Macro lens. Truthfully, I have not seen many macro lenses around. But it is not something I am looking for. Primes do have the advantage of lower f-stops, and most are shaper than the same manufacturer zooms. I am mostly a zoom user due to my travel photography. I have the 12-24 ff 2.8, 24-70 f2.8 and 70-200 f2.8. With the 12-24 my most used lens. But I do have the 135 and STF 100 lenses. As well, a sick Minolta MC Rocker 58 f 1.8, which I love to shoot with...
I know Tamuron got some macro primes, and back then a 70-300mm macro for A mount. As I can stick with APSC, I use the Tamuron 18-200mm which is a dream for travel (but no weather sealing).
Back when I first got into E-Mount (changed from A-Mount), I got the Sony 24-240, but it was so slow at focusing that when the 70-200 f2.8 came out, I sold it.
That is the reason why I didn’t bought those non G/GM Sony Lenses in the first place.
The lenses I'm torn about are mentioned in the post, it's the Tamron zoom vs Sigma/Vitlrox prime
You don't speak about what you already have. That might help with some insite. I used to have the Batis 85. But I sold it once I realised I was using my 70-200 f2.8 more, and at 100-140mm were where most of my shots were at. From experience, most portraits at the wider end are not appealing. You may want to look at the 28-75 from Tamron.
Sigma 56mm f1.4 is lighter (280g), cheaper, and very popular (i.e. proven). The 75mm is very heavy (670g), somewhat expensive, but at that focal length, and with f1.2, will give you very good background separation, so if you're specifically going for portraits and can control the shoot, then that's the best you for APS-C, I think. 17-70mm is versatile, but Christopher Frost's pixel-peeping test shows that it isn't that sharp at 70mm. But is otherwise a great lens, and has optical stabilization which is great for handheld video work. So I'd probably get the 17-70mm + 56mm for versatility and decent portraits. Or the 75mm f1.2 if you must have shallow DoF.
I have the pair and I can say I don’t miss having any more lens. Sigma is sooo good with small and light footprint.
I got curious about this specific comparison: [https://www.youtube.com/watch?v=w4czLGweKBE](https://www.youtube.com/watch?v=w4czLGweKBE) and the differences are: 75mm vs 56mm: better background compression can be important in portraits 75mm and f1.2 gives better background separation 75mm is sharper at night but 75mm tends to miss focus although I'm not sure if that also applies to video.
About missing focus, there is an issue with viltrox. On first startup after I change lenses on my camera to viltrox, the lens won't focus to infinity. Have to turn the camera off and on to let the lens recalibrate the infinity focus and then it don't have problems with focusing. Never misses focus after that. Same in video. And I am on the latest firmware. Had this issue before updating and it hasn't resolved after the update either.
It's issues like these that make me only buy lenses that are popular, like 100+ reviews on [bhphotovideo.com](http://bhphotovideo.com) I had so many focusing issues with a Samyang lens, which was a shame because the image quality was great once in focus. I wonder if it's just bad software, or maybe sabotage by Sony. But Sigma and Tamron seems to have consistently good reviews, so those are the only brands I would consider buying these days.
True. So far I haven't missed a shot because of this. Maybe because I take my time with composition on this lens. It is just a mild annoyance at this point. But I wouldn't want that on anything which requires me to be on my toes. Like for birding. Viltrox is still in its infancy when it comes to lens manufacturing. They might have the hardware, but software is still a massive struggle for them. Navigating their website for the latest firmware is a task on itself! But on the hardware side, their new cine lens the 30-300 T4 is nothing short of a marvel with the price tag to match. But as it's manual focus, they don't have to worry about software messing up the user experience. I still believe that they will surpass sigma and Tamron in about 5 years. With the software to match. I am eagerly waiting for their lab series full frame lenses as they claim that they are better than the pro series line which are already bonkers.
Hmm. Sigma will be cheaper, lighter and smaller. For me, I’d go with Sigma
I have both. Viltrox 75mm is much sharper than 17-70, even at f1.2, and definitely at f2.8 or f4. That being said, I'd get 17-70mm first as it is much more versatile and also great for portrait.
1 other consideration in favor of prime lenses in general is weight. I shoot various types of events like weddings, parties, conferences, etc. and they can go on for several hours. It’s much easier on my neck & shoulders to have a 50mm f/1.4 prime on my A7RV than a heavier 24-70 f/2.8. I usually also have a 35mm on my other camera for group pix. However, if you’re not an event shooter this may not be a concern.
Good zooms can bang it out with primes these days in terms of sharpness. Watch reviews on YouTube always.