EF 600mm f/4L IS III USM + TC Image Quality

[docusync]

Hi Friends,

Does anybody have first-hand experience comparing this lens to its predecessor the EF 600mm f/4L IS II?

Particularly I'm interested in the sharpness loss fact while it's paried to a teleconverter.

I'm in the market for the RF 600mm f/4 (which is optically identical to the EF v3) and already placed my pre-order but the IQ degradation reported by TDP https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1227&Camera=979&Sample=... and some other folks (like here https://www.flickr.com/photos/chrisbainbridge1/46627840622) is worrying me.

I'm not sure if that's an early batch issue or an actual design flaw. There is not much information on Google about it unofrtunately. I would buy a 600/4 II and call it a day, but they aren't available anwyhere. I'm planning to use the lens with a 1.4 TC all the time, and I don't like the idea of paying $13.5k (including the TC) for a subpar quality. I couldn't care less about the weight reduction, and wouldn't definitely sacrifice weight for the IQ.

Please share you expereince and samlpe shots if available.

Thanks!!!

[ebiggs1]

"I just use the 1.8x crop mode on my R5...it basically reduces the resolution and file size to 30mb."

I doubt the resolution is reduced or at best very little. You are using the same sensor just less of it. True "crop factor" like a Rebel has is using a totally different sensor. In fact the output might be better since you are in the sweet spot of the sensor electronics like the AA filter.  There should be less aliasing artifacts plus different output sharpening.

I bet you do see a smaller file but that is because you aren't capturing all the data the sensor can. Not because resolution is less.

[docusync]

@krispenhartung

Thank you for the offer! I would definitely appreciate it if you run some tests just to compare with my findings.

I got a loaner from CPS (thank you guys!!!), and the lens is marvelous. Long story short - I'm 100% keeping my RF600 preorder. While it's still kind of heavy at 3+ kg - it's much easier to hand hold it compared to the v2. Plus the balance shift towards the camera helps to aim quicker at moving subjects (birds!)  The AF is not as fast compared to the 100-500. I suspect it needs a higher voltage battery (1d-series or the upcoming R3), but the distance limiting switch and programmed AF points help a lot.

I kept the 1.4x III pretty much always mounted on the lens for my bird pictures, and made some test chart and £5 bill shots before returning the lens. I compared the test shots with my 200/2 (pure lens and +1.4X) and some other glass. The 600/4 III is a clear winner. While there is a slight drop in image "crispness" looking at 200%, it's not something to worry about. The 200/2 + 1.4x performs WAY worse. I sold my 300/2.8 II - otherwise I would compared to it as well. I could not get the same [bad] results as Bryan/TDP. For my tests I turned the IS off and shot with a strobe @ ~1/5000s t.1 or faster. I'll post the sample shots (and a link to the raw files) later, hopefully this weekend.

[docusync]

Here you go folks - the raw files, all EXIF metadata is there: https://drive.google.com/drive/folders/1r0tkuqV8yd74GrN7ItSgm_W8-oXFehQZ

Not the best charts but enough to get an idea.