Canon EF Lens to RF-mount speed booster ultra 0.71x questions

Imagery
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p.1 #1 · p.1 #1 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

Hello all,

I posted this in Gear talk but got no answer so let's try in here.
I would like to know if anyone has had experiences with this adapter.

- Auto focus: Does it work flawlessly in still or video? All I need is a reliable auto focus.
- Sharpness: If center sharpness is good, I am ok with that.

Other stuff like information display are non significant to me.

I am shooting mainly still, 90% photos and 10% video.
Canon R5 and lenses to be used with this are EF 300/2.8 is ii, EF 70-200/2.8 is ii and maybe EF 400/2.8 is ii or iii

Thank you.
Hai

Oct 25, 2023 at 03:37 PM

rscheffler
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p.1 #2 · p.1 #2 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

This interested me prior to the R7 release. I decided not to get the R7 and didn't continue my investigation. What is your intention with it on the full frame R5?

There's a thread here: https://www.fredmiranda.com/forum/topic/1762830/

And this link to Camnostic's review is in the above thread.

Oct 25, 2023 at 03:50 PM

Imagery
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p.1 #3 · p.1 #3 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

rscheffler wrote:
This interested me prior to the R7 release. I decided not to get the R7 and didn't continue my investigation. What is your intention with it on the full frame R5?

There's a thread here: https://www.fredmiranda.com/forum/topic/1762830/

And this link to Camnostic's review is in the above thread.

The main thing is to get a wider aperture, F2 if possible as I shoot often in near darkness.
And without having to invest more $$ into an 200mm F2 is.

Oct 25, 2023 at 04:01 PM

rscheffler
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p.1 #4 · p.1 #4 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

The 0.71x speed booster results in a smaller image circle roughly equivalent to APS-C. I haven't seen any reviews where someone used it on full frame without the crop, if that's what you want to do. If so, it's likely you'll get significant image quality falloff outside the APS-C circle and likely also significant vignetting, assuming the camera will even allow you to use it in full frame.

If you're a Canon Canada CPS member you can rent/test drive the speedbooster for evaluation.

Oct 25, 2023 at 04:07 PM

bman212121
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p.1 #5 · p.1 #5 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

It looks like someone over at DPReview has the answer you seek:

"
I use the canon .71 on my R5, works with every ef lens I have, I have a whole set of CN E's works on them to, it works on my manual focus Contax Zeiss, and my Otus 55 and Zeiss Classic 21mm, amazingly it works on the 8-15 and i get a full circle on the 8mm end, in crop mode. It is incredibly useful, If you get it and have an R5 test your lenses as some will cover 1/1 or 4/5 without vignetting, 4/5 gives you 30mp and you gain a stop.
"

https://www.dpreview.com/forums/thread/4702319

It sounds like you'll get to clear a warning message telling you it wasn't designed for your camera each time you use it, but it works nonetheless. It should retain a similar FOV as full frame (slightly more narrow in APS-C), but with more light for use in APS-C mode. Obviously if you're not in APS-C or shooting crop video formats, the outer pixels will have no light at all since it won't cover the full sensor.

I'm a bit torn if simply using a lower resolution full frame sensor wouldn't make more sense. On a per pixel basis if you had the same MP between full and APS-C + converter then the same amount of light would be hitting each pixel, except the native sensor wouldn't have any of the converter loss. The problem is the converter is making super 35, which would be around 22MP, but using APS-C mode on the R5 is about 17.6MP. The 0.71x converter is just a 1.4x TC ran in reverse, so it's 1.4x vs 1.6x crop factor so the converter is covering a sensor that is only 1.4x crop vs the actual crop which is 1.6x. So you're comparing a ~22MP super 35 to say an R6 MKII at 24MP, except in APS-C mode on the R5 you're only delivering 17.6MP from the 22MP.

Another way to word that:

R5 + speedbooster + APS-C mode will collect less light than R6 MK II on native. (Loss from image circle mismatch and optic loss). I honestly think that a R6 MKII or an R3 would turn in a better photo in this extreme example, because it's better matched to the lens.

Where it gets more nuanced is shooting full frame, but then using something like 1:1 square instead of 3:2. which would more closely match the image circle. Don't ask me my thoughts on that one because I honestly don't know how that would compare.

Oct 25, 2023 at 08:13 PM

Imagery
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p.1 #6 · p.1 #6 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

Oct 25, 2023 at 10:30 PM

Imagery
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p.1 #7 · p.1 #7 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

bman212121 wrote:
It looks like someone over at DPReview has the answer you seek:

"
I use the canon .71 on my R5, works with every ef lens I have, I have a whole set of CN E's works on them to, it works on my manual focus Contax Zeiss, and my Otus 55 and Zeiss Classic 21mm, amazingly it works on the 8-15 and i get a full circle on the 8mm end, in crop mode. It is incredibly useful, If you get it and have an R5 test your lenses as some will cover 1/1 or 4/5 without vignetting, 4/5 gives you...Show more →

Thank you for your reply and the link.
It's very informative!!
Hai

Oct 25, 2023 at 10:31 PM

rscheffler
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p.1 #8 · p.1 #8 · Canon EF Lens to RF-mount speed booster ultra 0.71x questions

rscheffler wrote:
The 0.71x speed booster results in a smaller image circle roughly equivalent to APS-C. I haven't seen any reviews where someone used it on full frame without the crop, if that's what you want to do. If so, it's likely you'll get significant image quality falloff outside the APS-C circle and likely also significant vignetting, assuming the camera will even allow you to use it in full frame.

If you're a Canon Canada CPS member you can rent/test drive the speedbooster for evaluation.

Imagery wrote:
Thank you for your reply.
Yeah that's why i wonder i always read APS-C and not full frame with this adapter.
Hai

Yes, the image circle is 'squeezed' smaller by 0.71x times, which concentrates the light forming the image into a smaller area, hence the reason you 'gain' one stop. It's like a tighter spotlight beam is brighter than when set to flood/wide. So maybe you gain a stop in this respect, but you're covering a smaller part of the sensor and therefore getting a lower resolution image. It would be an interesting test to see what, if any, differences there are. It would also be interesting to see how the native, noisier full frame R5 image responds to modern noise reduction, such as Adobe's Denoise, DxO, Topaz, etc vs. the speedbooster image.

Oct 25, 2023 at 11:41 PM


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