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Sony A9 vs Sony A7R mk IV (1 Viewer)

49bentley

Well-known member
Canada
I need some advise/help. Most of my pictures are of birds (99.5%). I currently use a Canon 7D mk II with Canon a 100-400 mm mk II. The pictures are good but I want to up the quality. I am considering going to a Sony mirrorless. Which would give me the best quality pictures, Sony A9 vs Sony A7R mkIV, when mated with a Sony 400mm f2.8 with 2x TC. Please note that with birding there can be heavy cropping.
 

etudiant

Registered User
Supporter
That is a serious investment either way.
Perhaps you might rent the system for a few days to see how you like it first, maybe as part of a trip.
Lens Rentals ( https://www.lensrentals.com ) is a good option here in the US, but I don't know if they serve Canada.
 

marcsantacurz

Well-known member
The A9 will give you cleaner images and be easier to use because the sensor sites are so large. You'll get better ISO performance and be less vulnerable to shaking blurring the image. You will also be able to use higher f-stops, like f/11 or f/16 without diffraction limits. But, you will be limited to about a 1.5x - 2x crop (11MP - 8MP after crop).

The A7RIV will give you more crop, but remember that MP go down as the square of the crop, so a 61MP with a 2x crop is only 15.25MP. That said, you can probably go to a 2.47x crop (10MP) and have nice images. The down side is the pixel size is very small. You will start getting diffraction blurring around f/5.6 and significant diffraction around f/8. Because the pixels are so small, they will get blurred from smaller angular deflections (i.e. shake). That diffraction is not often visible in a full sized photo until it gets pretty bad or you make a really big print or you crop a lot. If you're going to crop heavy, you really need to keep the f-stop at f/5.6 or less (maybe 6.3 or 7.1 is passable).

The A7RIV needs to be used with very high resolution lenses because the sensor has needs to see as many lines per inch as it can. The 400mm f/2.8 should be fine!

So, in summary, the A9 should crop to 1.55x for a 10MP image and the A7RIV should crop to 2.47x for a 10MP image. So you get 1.6x more crop out of the A7RIV. That's it for all those pixels -- it's the curse of MP reduction going as (crop^2).

400mm * 2x (tc) * 1.55 = 1240mm @ 10MP or 1736mm @ 5MP
400mm * 2x (tc) * 2.47 = 1976mm @ 10MP or 2766mm @ 5MP

So you gain 736mm at the cost of less diffraction free f-stops, worse ISO performance, and truly giant files. It will also need better shooting technique, higher shutter speeds, or some sort of support more than the A9. Of course, you could crop down to say 5MP or even 2MP. I've done that on the d850 (42MP) and still get perfectly good images, as long as I don't try to enlarge them too much or expect them to cover much screen real estate.

I went from the d500 to the d850 because I basically have the same pixel pitch (it's a little smaller on the d500) and can shoot FF when I don't need to crop and it has slightly better IQ, im my opinion. So that's kind of the A7RIV approach.

Shooting at f/5.6 at 1/2000th on a sunny day will be around ISO 100 - 200. No problem. Overcast day, maybe ISO 800 - 1600. Around sunset ISO 1600 - 6400 or higher if shooting into shadows. Dark subjects might need another 2x ISO.

My understanding of the A9 (I've not shot it) is it is virtually noise free up to ISO 6400 and only minor noise upto 25,600. I am not sure what the A7RIV will be like, but I bet it will be more like ISO 1600 or 3200 for noise free. REmember that when you crop heavily, the ISO noise really jumps out (literally it's magnified!). So, you might not get better IQ from crops in poor lighting, and remember you'll need to shoot at a higher shutter speed to keep the shake to a minimum for all those tiny pixels.

The A7RIV is mostly a landscape and studio camera, IMO, but if used well I am sure it can give you some excellent wildlife shots (though Lloyd Chambers says the broken focus stacking makes the A7RIV a poor choice for landscape). Personally, I use a high resolution camera and crop a lot, so I'd probably be in the A7RIV boat. But 61MP might be getting hard to use compared to the 42MP I'm at right now. The safe choice is the A9, but you'll lose about 1.6x crop compared to the A7RIV.

Sorry I don't have a simple answer. It is all going to be tradeoffs. I don't think you'll see many pros using an A7RIV for action or sports. It can only do 68 exposures (JPEG) before the buffer craps out. I don't know why they didn't use XQD. And for high frame-rate shooting over a few hours, 61MP file sizes just won't fly.

Marc
 

Chosun Juan

Given to Fly
Australia - Aboriginal
Also, there is an a9 II on the way very shortly. Unknown resolution at this stage, but more than 24MP - maybe even up to 36MP? The next generation AF should be next level !

There will also be a Canon 1DX III flagship within about 6 months - perhaps that's an option too with 400 f2.8 III + 2XTC, or 600 f4 III + 1.4xTC. You could also stick either of those lenses on the rumoured high resolution 'R' camera (~80MP?) when it gets here though that might be 12 months or more away ....

The same things that Marc explained quite well apply, and I agree with Etudiant - you'd definitely want to try those rigs out first. Do you intend to handhold? or mostly tripod? and gimbal?



Chosun :gh:
 

49bentley

Well-known member
Canada
Thanks etudiant , marc, and Chosun. This is such a tough decision. I believe the best result for me would be to wait a few months (?) for the Sony A9 II.
 

GYRob

Well-known member
Iv been back and forth a9 or A7rIv to use with the 200/600 -a9 I would need a tc too so after many reads and the tube videos with so much cropping available It will be the A7rIv and no tc I think the lens will only resolve 50mp but that's enough, My 5dsr ( just sold) has that .

Then If the a9 II comes out I may well get that as it too will have the latest tec .

Rob.
 

marcsantacurz

Well-known member
You know, the A7RIII is a perfectly good camera at 42MP, and I know from my d850 experience that can work well for birds and action. The A7RIII will do 76 continuous exposures @ 10FPS (I only get 9FPS on the d850) with raw. from what I understand, it got a big AF boost the last firmware update too. And you'll find a lot of used ones now and get a deal, or take advantage of the Sony $500 savings on a new one.

I understand it's not as sexy as an A9 or A7RIV, but I know it will give good results. 42MP will get diffraction limited beyond f/8, but f/8 is good for fastish lenses (like the 500mm f/5.6 or the 400/2.8 + 2x TC options) and gives quite a bit more DoF.

To use my previous calculations:
24MP: 400mm * 2x (tc) * 1.55 = 1240mm @ 10MP or 1736mm @ 5MP
42MP: 400mm * 2x (tc) * 2.05 = 1640mm @ 10MP or 2296mm @ 5MP
61MP: 400mm * 2x (tc) * 2.47 = 1976mm @ 10MP or 2766mm @ 5MP

The other thing to think about DoF is this. The A7RIII has a pixel pitch of 4.5 um and the A7RIV has 3.7um. What that means is you lose about 1 stop of DoF on the A7RIV -- a smaller airy disc will cause the same DoF blur as a larger disc on the A7RIII. The A9 is about 6um.

One way to think about this, is one usually needs the defocus blur to be < 2x pixel pitch (George Douvos). The A7RII (and d850) can take a blur of about 9um and the A7RIV of about 7um. The Sony A9 can take around 12um.

Here's some example numbers. To extrapolate to longer distances, it goes more or less as the square (e.g. 0.14m @ 10m ~ 14m @ 100m).

Code:
A9    : 400/2.8 x2 at 10m is 0.020m DoF, at 20m is 0.08m, at 40m is 0.33m
A7RIII: 400/2.8 x2 at 10m is 0.017m DoF, at 20m is 0.07m, at 40m is 0.27m
A7RIV : 400/2.8 x2 at 10m is 0.012m DoF, at 20m is 0.05m, at 40m is 0.20m

The same thing at f/8:
Code:
A9    : 400/4   x2 at 10m is 0.030m DoF, at 20m is 0.12m, at 40m is 0.47m
A7RIII: 400/4   x2 at 10m is 0.020m DoF, at 20m is 0.09m, at 40m is 0.38m
A7RIV : 400/4   x2 at 10m is 0.017m DoF, at 20m is 0.07m, at 40m is 0.28m

So without getting into diffraction limitations, you will have a pretty shallow DoF at mid-range distances for the A7RIV at 800mm (10-20m), especially compared to the A9.

Lloyd Chambers puts it like this: compared to the A7RII you should stop down 1 stop more for similar DoF, but to avoid diffraction you want to stop down 1 stop less. Basically, you are squeezed from both sides.

So in summary, the A7RIV will let you crop about 1.6x more, but you also have about 1 stop more DoF blur unless you start getting diffraction limited beyond f/5.6. I think it's going to be a pretty small operational window for the the 61MP sensor, especially for larger birds that you might want to try and get mostly in focus and thus need f/8 or f/11 -- you might lose that to diffraction especially if cropping heavily.

I go into all this detail because your goal is to improve image quality with very long focal lengths (800mm) and heavy cropping. Unfortunately, more MP is not always better, but if you can shoot the A7RIV in the goldilocks zone it should give stunning images.

Marc
 

GYRob

Well-known member
Some very good points but I like to have the New tec (although its not New for long ) just to keep ahead for a little time :)
I have just ordered the A7r IV and 200/ 600 hopefully being new to Sony it will work out ok .

Rob.
 

marcsantacurz

Well-known member
I'm sure you'll enjoy it!

I might be tempted by the A7000 + 200-600.

The file size of 61MP scares me. It already takes a long time to process the 42MP from the d850. I'd likely need to upgrade my little Macbook Air to deal with the A7RIV raw files.

marc
 

Vollmeise

Well-known member
(...) I think the lens will only resolve 50mp but that's enough, (...)

Rob, I'm useing the new SEL 200/600 with a Sony A6400 since a couple of weeks now w/ and w/o teleconverter.

W/o teleconverter the 200/600 delivers pin sharp images even wide open useing the 1.5x crop A6400. That is a resolution of (1.5 x 1.5 x 24 mp) 54 mp.

W/ 1.4x teleconverter the images do show more details, but the resolution improvement is lower than it should be in purely arithmetical terms (maybe due to diffraction and / or the A6400's AA-Filter).

So that means, the 200/600 resolves > 54 MP for sure.

Please let us know how the new stuff performs, maybe with some 100% crop samples?

Thx a lot!
 

capdegat

Well-known member
Rob
I'm about to pull the plug on a mk iv with probably the 100-400 due to weight considerations. I coming from d850 etc so how are you getting along ?
 

Chosun Juan

Given to Fly
Australia - Aboriginal
Rob
I'm about to pull the plug on a mk iv with probably the 100-400 due to weight considerations. I coming from d850 etc so how are you getting along ?
Les, wouldn't the D850 with a PF 500 f5.6 be about the same weight and give much more reach and performance?



Chosun :gh:
 

capdegat

Well-known member
Chosen
Much as i love the nikon combo I really need a zoom for my type of pics. the 200-500 is too heavy, the 80-400 isn't sharp at 400 from what I've read and that's about it . I could go tamron/sigma but big lenses are too heavy and 100-400 didn't give me what i wanted . Canon 100-400 could but never been happy with crop canons and 5d doesn't give range .It seems like I've been looking for solutions forever !! Don't get me started on m43or fuji either !Semi desperation leads me to sony which I wouldn't even think about before based on ergonomics alone but mk iv seems to overcome most of my objections. We shall see.
 

marcsantacurz

Well-known member
Lloyd Chambers has his A7RIV and has started his typical highly detailed testing. If you are not a subscriber, you can subscribe to just his Mirrorless section ($99/yr, not auto-renewing). It's worth it for his lens and camera reviews.

https://diglloyd.com/prem/prot/ML/SonyFullFrame/SonyA7R_IV.html

His initial conclusions is that 60MP is brutal on lenses and needs very high quality. Even small curvature is exaggerated by the high resolution. But you get a ton of detail! He does approach it from a fine-art landscape viewpoint, not sports/wildlife. This means most of the lenses he tests are shorter focal lengths.

His main gripe is that the Sony focus stacking is broken, in his opinion. For his work at such high resolutions, he needs focus stacking to get depth of field. Sony does not do in-camera stacking (like the Fuji GFX), so you end up needing 4x or 16x the number of (giant) images for each stacked image. And Sony does not do lossless raw compression. There are also some technical issues with the stacking he does not like.

He finds that with the best lenses, you will start to notice diffraction around f/4.5. With lower quality lenses, it might start to be noticeable by f/5.6 or f/8 (due to the overall less good IQ). He thinks the practical limit is f/5.6 for the A7RIV as the added DoF outweighs the small diffraction cost at f/4.5.

Diffraction will show up as blurring very small details at first. What he calls micro-contrast. If you are not going to blow things up to giant size or crop heavily, you might not notice it until higher f-stops (but then why 60MP?). But if you are critical about the IQ, you'll notice it.

The other issue, as I've mentioned before, is you will lose DoF compared to the A7RIII. Remember, DoF works like diffraction, it's blurring an image and the smaller the photosites the more sensitive the camera is to DoF effects. But whereas you want to open up to improve DoF you want to stop down to reduce diffraction, so you end up with a small window of usable apertures.

That said, I'd love to try the camera with the 400/2.8 and with TCs or the 600/4. I'm not sold on it with the 200-600 f/6.3 but it might be OK with some diffraction, as long as you don't need to stop down much for DoF. I am sure that I will rent it and try it out, too good to pass up! I am just concerned that 35 - 45 MP might be a more optimal pixel pitch for long lenses that need higher f-stop for DoF (or just their f/6.3 limits) if not using the super exotics f/2.8 or f/4.

Marc
 

GYRob

Well-known member
Im still waiting for the 200/600 I have the a7r4 and it does seem to be a great camera (just have a kit lens ) to try it with hopefully my lens will come next week .
Rob.
 
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