RF 600mm f/4 L IS USM

[neuroanatomist]

Copy variation definitely occurs, it’s more common in consumer lenses than L series lenses, but certainly occurs in the latter. For example, check out Bryan’s review of the EF 24-70/2.8L II. He ended up testing four copies of that lens because the first two did not perform well. When I was reviewing the EF-M 18-150 for TDP, my results differed substantially from Bryan‘s posted ISO 12233 chart images. He ordered another copy and tested it, found it was significantly better, and replaced those images in the tool.

I did test my RF 1.4x and 2x with the RF 100-500, and the results were as expected, so I don’t think there’s an issue with my RF 2x. In real world shooting, I’m not sure those differences would be evident anyway. But I do definitely recommend testing a new lens when you get it.

[Fast Glass]

Indeed. I have seen sample variation in lenses I have owned as well.

[HDNitehawk]

Copy variation definitely occurs, it’s more common in consumer lenses than L series lenses, but certainly occurs in the latter. For example, check out Bryan’s review of the EF 24-70/2.8L II. He ended up testing four copies of that lens because the first two did not perform well. When I was reviewing the EF-M 18-150 for TDP, my results differed substantially from Bryan‘s posted ISO 12233 chart images. He ordered another copy and tested it, found it was significantly better, and replaced those images in the tool.

I did test my RF 1.4x and 2x with the RF 100-500, and the results were as expected, so I don’t think there’s an issue with my RF 2x. In real world shooting, I’m not sure those differences would be evident anyway. But I do definitely recommend testing a new lens when you get it.

I went through multiple copies of the EF 24-70 f2.8 II before I found a pristine one. Big primes I think are held to higher level of Quality Control.

The discussion about the RF 2x I think started with Brant.
It wasn't a problem with the RF 2x, it appears to perform better than the EF 600mm III version with a 2x.

https://www.the-digital-picture.com/...mp=2&APIComp=2

[neuroanatomist]

It wasn't a problem with the RF 2x, it appears to perform better than the EF 600mm III version with a 2x.

https://www.the-digital-picture.com/...mp=2&APIComp=2

The difference is that Bryan's comparison is using different cameras with (slightly) different resolutions and different OLPFs (the 5DsR has a 'self-canceling' AA filter, the R5 has an AA filter (not sure if it's the newer design used on the 1D X III that has four layers instead of two), and Canon's DPP sharpens up AA filtered images very well.

When I compared the EF 2xIII with the RF 2x, I found the former to be sharper when using the same lens on the same R3 camera, with identical processing – pretty much the most apples-to-apples comparison possible, for the given sensor resolution (which is significantly lower than the 45-50 MP of the 5DsR/R5).

[HDNitehawk]

The difference is that Bryan's comparison is using different cameras with (slightly) different resolutions and different OLPFs (the 5DsR has a 'self-canceling' AA filter, the R5 has an AA filter (not sure if it's the newer design used on the 1D X III that has four layers instead of two), and Canon's DPP sharpens up AA filtered images very well.

When I compared the EF 2xIII with the RF 2x, I found the former to be sharper when using the same lens on the same R3 camera, with identical processing – pretty much the most apples-to-apples comparison possible, for the given sensor resolution (which is significantly lower than the 45-50 MP of the 5DsR/R5).

Many variables at play. If I understand your testing you are using EF lenses.
It sounds like you have a fair comparison of an EF lens with both adapters.

The question I see raised, does the RF adapter play better with the RF lenses. I doubt it does, I think some of the EF 600mm III comparisons were because of a weak lens.

To your first point, if the EF 600mm III had been tested with a R5, and the RF 600 tested with a RF it might be a very comparable test.

Looking at Bryans test the EF 600mm II vs the RF 600mm with 2x the center is better on the EF and the Periphery on the RF.
https://www.the-digital-picture.com/...mp=2&APIComp=0
Then the difference between the RF 600mm and the EF 600mm II.
https://www.the-digital-picture.com/...mp=2&APIComp=0

Looking at all the charts it appears that there might be an issue with the EF 600mm III tested. If it is a soft lens the 2x would magnify the softness.

My RF extenders show up tomorrow, it might be interesting to see how the RF 600mm stacks up against the EF 500mm II at the same and equal framing distances.