Photogrammetry - camera choice
interpolator
so, i'm not really a camera geek, thats why i am hoping to get some unbiased tips here
right now i am using a canon 650D with a sigma art lens for phtogrammetry, but it has some problems finding focus points on dark subjects or low light situations, and higher iso looks really terrible on the 650D
so iam thinking about getting a new camera, its really 50% because i am not satisfied with my canon right now and 50% because i like new shiny things
i have been thinking about a sony and there are a few models i would consider :
a7III
a7RII with the zeiss 55 lens
cybershot RX1R II
now i am not sure if the 42mp from the a7RII will yield visibly better results than say from the a7III which has "only" 24mp but overall better features. The cybershot sounds really nice on paper, but has a fixed 35mm lens, which is fine for photogrammetry, but limits its usage somehow... also the german pricetag is absurd with 4800$..... (compared to 3300$ on the american website)
or should i wait for something completly different ?
Replies
Yeah the 650D is old with a pretty crappy Canon sensor. Canon sensors are generally pretty bad compared to Sony ones, especially the old ones. I think Canon has started to use Sony sensors recently, at least in some of their cameras.
Overall, the A7III is an amazingly good camera for the money. Saying that, if you can find it for considerably less, the A7II is very, very good as well. Basically the A7II is fantastic and the A7III is absurdly good, in terms of image quality (dynamic range, noise in low light/high ISO).
Here's a link that compares the A7 III, A7r II and 650D (go to measurements): https://www.dxomark.com/Cameras/Compare/Side-by-side/Sony-A7-III-versus-Sony-A7R-II-versus-Canon-EOS-650D___1236_1035_813
You'll note that the A7R isn't really better than the A7III, except that it has more pixels. Whether you need 42 vs 24 MP really depends on what you're doing. If you need a lot of single shot resolution, the A7R series is what you want. If you're doing 3D photogrammetry, you're probably taking many images, which means you're getting much more detail and resolution than with a single image, so single shot resolution isn't very important (8MP is probably all you need in this case).
If you're building a scanner for flat surfaces where you need as much single image resolution as possible, then the A7r's 42 MP would be useful, but other than that, you can go for the cheaper A7 series.
The Zeiss 55/1.8 is a very good choice, it's pretty sharp corner to corner even wide open and resolves very well stopped down.
The RX1 line is interesting if you can live with a 35mm lens. But yeah the pricing is really too high for these IMO. Something like the A7II or A7III will be a lot more versatile.
An important note: even modern super cameras like these Sonys will not produce great results in low light. You're not going to get images suitable for photogrammetry at ISO 6400. You'll want to stick to ISO 100-400 to get the best out of these (or any) camera. So if you're in low light, you probably want to use a tripod, or use a slower shutter speed and rely on image stabilization (if relying on IS at low shutter speeds, make sure to take a few shots to make sure you get one good one).
Also, with a fullframe sensor, you'll need to stop down about 1 stop more vs aps-c to get the same DOF. So with your Canon maybe you could shoot at ISO 400 5.6, for the Sony you would have to shoot at ISO 800 F8. The Sony is probably at least two stops better so it's still going to be better overall, but don't expect miracles. Again, this puts pressure on some sort of support or stabilization system for low light.
At the end of the day, I would go with the A7III + CS 55/1.8, but I would consider the A7II if you can find a good price on a used one too (going rate is $800-900 on eBay in the US).
Less money on camera body means more money for lenses! If you're generally interested in photography as well, I would suggest investing more into lenses than camera bodies. Lenses enable you to take entirely different types of photos, can be used with new cameras, and typically hold their resale value a lot better than cameras too. Camera bodies drop in value as soon as you take them out of the box. =P