Sony appears to have dropped the price of the A7Rii by $500 with the announcement of the A9. I am tempted to skip my planned upgrade from A6000 to the A6500 and make the leap to the A7Rii. However I currently have only have one FE lens – the excellent 90mm Macro. I would be relying mostly on using my APS-C lenses in crop mode on the A7Rii for a while until I gradually acquire some decent FE lenses. I also have some legacy full frame Olympus OM lenses which I could use, but they are a bit long for my main interest which is landscape / travel.

My question is, will the IQ of the APS-C lenses in crop mode on the A7Rii be any better or at least as good as on my current A6000? I would be happy with ‘as good as’. I am thinking in terms of color depth, noise, high ISO and dynamic range. I understand that the APS-C lenses will not realize the full potential of the A7Rii. Please, no need to go into explanations of pixel count, crop factor, angle of view, equivalent focal length, depth of field etc – just interested in IQ. Large prints are not a concern either.

I asked the Sony ‘expert’ at my local Best Buy about APS-C lenses on the A7Rii and all he would say is ‘it is not recommended’. I don’t know why.

I had the same questions and concerns when I bought my a7R and planned to adapt my a-mount Sony lenses. Some of my lenses were very good but they were DT, or crop lenses. You can use crop lenses on an a7Rii, but you may get vignetting, even severe with some lenses. Some zooms will vignette at some focal lengths but not others. You can mitigate this either of two ways: accept the vignette, then crop in post; or shoot in crop mode and accept 18MP. The results are about the same.

18MP isn't bad. Is it as good as an 18MP image from a crop sensor? How about from a 24MP crop sensor? The a7Rii's sensor is better than the a6k's sensor in more ways than just megapixel count, but the pixels are smaller than those on the tightly-packed 24MP sensor. Pixel size matters, of course, but it matters less in the absence of an AA filter, as on the a7Rii. Check out this comparison of an a6k with an a7R (not the mark 2) in crop mode:
https://www.getdpi.com/forum/sony/50813-a7r-crop-mode-vs-a6000.html

I don't know why the a7R shoots only 15MP in crop and the a7Rii shoots only 18MP when logic says that with a 1.5x crop factor, they should shoot at 16MP and 28MP, respectively. One would think that shooting full frame, then cropping in post would offer a better image, but that may not be. For example, I love my walk-around Sigma 18-250 on my a77ii, but it's a crop lens. I've used it on my a7R in crop mode and I have no complaints, but my son inadvertently tested it in full-frame mode on my a7R and got severe vignette - a round image. If I were to crop it, there would be very poor res at the edges due to the refraction distortion inherent in such an image, so I would need to crop further, discarding much of the actual image. Though I haven't checked, I'm guessing that such cropping would result in a 15MP image. It appears Sony designed its crop mode for the most severe possible vignette to ensure the best overall image quality. I'll attach two images as examples. The first is a selfie my son took at 18mm while we enjoyed Yellowstone last June, and the other is a shot of a couple bears at 250mm the same day. Notice the different degree of vignette at different focal lengths. My subjective opinion is that in low light, the a7R in crop mode outperforms the a77ii, but in bright daylight there is little difference.

I hope this is helpful even though my experience is with different cameras (though the a6k sensor is the same, I believe, as the a77ii). And for what it's worth, I'll add a couple links about other legacy glass adapted to FE bodies. After my Sony G glass and Samyang/Rokinon, there are a few Minolta-era lenses I love. On the long end is the 75-300mm "New." Not the Beer Can, Not any other of the four or five available, but the "New" model (that is its official Minolta designation). You can see an image and get more info here:
http://www.dyxum.com/lenses/Minolta-AF-75-300mm-F4.5-5.6-New_lens53.html

By the way, Dyxum is an excellent resource for info on Sony/Sony-mount lenses.

Quickly, two others I highly recommend are the Minolta 35-105mm f3.5-4.5 original (1985 release, so if interested check Dyxum for a picture) and my walk-around lens on my a7R: Tamron 35-135mm f3.5-4.5 Tele Macro. This lens never ceases to amaze me. It is a rare find, so prices vary wildly, but it can be had for a pittance. I got mine on eBay for around $60 shipped. The other two Minolta lenses I mentioned are fairly common for well under $100.

Finally, a couple more links about legacy glass I found useful. You might find a lens or two you can use until you build your arsenal of pricey FE lenses.

https://outfor30.com/2014/12/19/old-timers/

https://luminous-landscape.com/sony-a7r-wishful-thinking/

I've got the A6000, the A6300, and the A7R2. I rarely use the A6000 and the A6300 because image quality with the A7R2 is so much better for the large prints (20"+) I sometimes do.

The A6500 won't be any better for landscapes than the A6000. The A6500 is primarily for sports and wildlife with a long (300mm+) lens.

For landscapes, you need a wide angle lens and a good tripod. 24MP of your A6000 is fine for anything printed at 15" or less. I think you would be better off spending your extra money on a good wide angle prime lens and a good tripod.

The downside is that in crop mode you will have less pixels using the A7 than the Sony a6000, but then not by much. The upside is that the sensor is massively better than that of the a6000. Faced with a choice between the a6500 and the A7rII I would go with the latter in a heartbeat. I used and still use a few DX lenses on a Nikon D800 and am totally satisfied with the results. I had a Sony a6000 and it sucks in comparison to the Nikon D800--and the sensor in the A7rII is even better than that in the Nikon.

I assume that the A7 has a crop mode so you don't have to deal with cropping every shot manually later using a crop-sensor lens. If that is true I see absolutely no reason not to go with the A7rII, and plenty of reasons not to go with the a6500.

I had the same questions and concerns when I bought my a7R and planned to adapt my a-mount Sony lenses. Some of my lenses were very good but they were DT, or crop lenses. You can use crop lenses on an a7Rii, but you may get vignetting, even severe with some lenses. Some zooms will vignette at some focal lengths but not others. You can mitigate this either of two ways: accept the vignette, then crop in post; or shoot in crop mode and accept 18MP. The results are about the same.

18MP isn't bad. Is it as good as an 18MP image from a crop sensor? How about from a 24MP crop sensor? The a7Rii's sensor is better than the a6k's sensor in more ways than just megapixel count, but the pixels are smaller than those on the tightly-packed 24MP sensor. Pixel size matters, of course, but it matters less in the absence of an AA filter, as on the a7Rii. Check out this comparison of an a6k with an a7R (not the mark 2) in crop mode:
https://www.getdpi.com/forum/sony/50813-a7r-crop-mode-vs-a6000.html

I don't know why the a7R shoots only 15MP in crop and the a7Rii shoots only 18MP when logic says that with a 1.5x crop factor, they should shoot at 16MP and 28MP, respectively. One would think that shooting full frame, then cropping in post would offer a better image, but that may not be. For example, I love my walk-around Sigma 18-250 on my a77ii, but it's a crop lens. I've used it on my a7R in crop mode and I have no complaints, but my son inadvertently tested it in full-frame mode on my a7R and got severe vignette - a round image. If I were to crop it, there would be very poor res at the edges due to the refraction distortion inherent in such an image, so I would need to crop further, discarding much of the actual image. Though I haven't checked, I'm guessing that such cropping would result in a 15MP image. It appears Sony designed its crop mode for the most severe possible vignette to ensure the best overall image quality. I'll attach two images as examples. The first is a selfie my son took at 18mm while we enjoyed Yellowstone last June, and the other is a shot of a couple bears at 250mm the same day. Notice the different degree of vignette at different focal lengths. My subjective opinion is that in low light, the a7R in crop mode outperforms the a77ii, but in bright daylight there is little difference.

I hope this is helpful even though my experience is with different cameras (though the a6k sensor is the same, I believe, as the a77ii). And for what it's worth, I'll add a couple links about other legacy glass adapted to FE bodies. After my Sony G glass and Samyang/Rokinon, there are a few Minolta-era lenses I love. On the long end is the 75-300mm "New." Not the Beer Can, Not any other of the four or five available, but the "New" model (that is its official Minolta designation). You can see an image and get more info here:
http://www.dyxum.com/lenses/Minolta-AF-75-300mm-F4.5-5.6-New_lens53.html

By the way, Dyxum is an excellent resource for info on Sony/Sony-mount lenses.

Quickly, two others I highly recommend are the Minolta 35-105mm f3.5-4.5 original (1985 release, so if interested check Dyxum for a picture) and my walk-around lens on my a7R: Tamron 35-135mm f3.5-4.5 Tele Macro. This lens never ceases to amaze me. It is a rare find, so prices vary wildly, but it can be had for a pittance. I got mine on eBay for around $60 shipped. The other two Minolta lenses I mentioned are fairly common for well under $100.

Finally, a couple more links about legacy glass I found useful. You might find a lens or two you can use until you build your arsenal of pricey FE lenses.

https://outfor30.com/2014/12/19/old-timers/

https://luminous-landscape.com/sony-a7r-wishful-thinking/