chrysoberyl said:

What size is the image circle?

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Oh, man -- that's a can of worms...

AlanF said:

Agreed for uwa lenses. In practice, this is true for up to 35mm focal length, fading to hardly any difference at 50mm and all gone by 85mm. Even so,I really don't understand the high prices for some EF big white lenses unless people are still using DSLRs for the other reasons you suggest.

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The benefit of the short 20mm flange distance is most significant for wide-angle lenses. For lenses like my TS-E 17mm f/4L or EF 14mm f/2.8L II USM the mirror box in DSLRs forced designers to use complex "Retrofocus" designs. Moving the rear glass closer to the sensor in RF wide-angles allows light to strike the sensor more perpendicularly, reducing vignetting and corner smear. As you noted this physical advantage decreases as focal lengths increase. For telephoto lenses like my EF 300mm or EF 500mm the light rays are already largely parallel so the short flange distance provides little to no optical benefit.

High prices for "Big White" EF lenses (such as the 2008 EF 200mm f/2L IS USM or 2011 EF 400mm f/2.8L IS II) remain high for three reasons:

Optical Perfection: Lenses like the 2018 EF 400mm f/2.8L IS III use the exact same optical glass formula as the newer 2021 RF 400mm. Since the glass is the same there is no optical reason to pay double for the RF version if you already own the EF version.

Adaptability: These lenses work perfectly on the EOS R1, R5 Mark II and R7. While they are limited to roughly 7 to 10 fps (depending on the model and battery) the Dual Pixel AF makes them focus more accurately than they ever did on a DSLR.

Build Quality: These lenses contain large amounts of expensive Fluorite and UD (Ultra-low Dispersion) glass. The cost of raw materials and the precise manufacturing required for super-telephotos does not drop just because a new mount exists.

The EOS R1 and R5 Mark II can drive the focus motors of "Big Whites" with more voltage than older DSLRs. This often results in faster "Initial Acquisition" (the time it takes to first find the subject). However the 12-pin communication of native RF lenses is required for the R1 to hit its full 40 fps potential. My EF 800mm f/5.6L IS USM for example will be limited in burst speed but the Eye-Control AF on the R1 will still lock onto a bird's eye with 100% precision through the adapter.

"no word yet on an L-mount or Nikon Z-mount version of this lens."

(Sarcasm) If Nikon is blocking this third-party lens, everyone should get mad and quit buying Nikon cameras.

Etnaphele said:

But are they really so perfect? ....I see the point and find it fascinating, but if they miss the mark, the whole product just doesn't succeed in its already very niche role.

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Good question! I hope that reviews will give us an answer!
Canons 3rd party politic is recently supporting Zeiss as they are the only high-quality 3rd party lens manufacturer for the RF mount (full-frame).
I would like to see the New Sigma 35/1.4 lens on my Canon camera as manual-RF or adapted EF, but Sigma is obviously not going into that direction.

Old Man FL/FD said:

The Zeiss Otus series are close to perfect ‘optically corrected’ lenses.

These have all metal tight tolerance construction. The resultant lens group mass precludes a practical implementation of either auto focus or image stabilization. IBIS only.

Also, the necessary movement required for image stabilization will slightly degrade the optical correction.

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Not necessarily, it depends on the mass of the lens group used for OIS !
And don't forget the Leica SL AF lenses, did you ever test their 20mm f/2 Apo?

dolina said:

Hello AlanF, long time no hear! Thank you for your input on lens design.

The EF and RF mounts share a 54mm inner diameter but the flange focal distance is significantly different. The EF mount requires a 44mm gap to clear the mirror box while the RF mount is only 20mm from the sensor. This shorter distance allows RF lens designers to place much larger rear glass elements closer to the sensor. This design principle called telecentricity ensures light rays strike the sensor at a more perpendicular angle.

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Agreed for uwa lenses. In practice, this is true for up to 35mm focal length, fading to hardly any difference at 50mm and all gone by 85mm. Even so,I really don't understand the high prices for some EF big white lenses unless people are still using DSLRs for the other reasons you suggest.

stillviking said:

Non-sense: 1200mm is a "special" lens that sells close to zero. 400mm is a normal tele focal length.

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Oh dear. Are you deliberately missing the point? Why fixate on 400mm when we are discussing a lens that goes to 600mm?

Hint: f/5.6 is just a ratio. At 600mm it equates to a roughly 107mm diameter front element. Which is approximately 2.25x the area of a 400mm f/5.6 (~9016mm^2 versus ~4007mm^2) - a lot more glass, with implications for cost. To say nothing of zoom versus prime, non-IS versus IS, or inflation.

Extra hint: I bring up the 1200 as an extreme example to show how ridiculous your "point" was. Clear enough now?

Old Man FL/FD said:

The Zeiss Otus series are close to perfect ‘optically corrected’ lenses.

These have all metal tight tolerance construction. The resultant lens group mass precludes a practical implementation of either auto focus or image stabilization. IBIS only.

Also, the necessary movement required for image stabilization will slightly degrade the optical correction.

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But are they really so perfect? The tests of the 50mm were pretty underwhelming last year (LoCa is one flaw I remember). I see the point and find it fascinating, but if they miss the mark, the whole product just doesn't succeed in its already very niche role.

zardoz said:

I've played with the in-camera upscaling as I feel like I was probably the only person on earth who used the IBIS-operated high resolution mode on the R5, and I've found that it adds detail that's not present in the original scene (even on the RF 85 1.2L). As with most AI-driven technology, you're not actually adding anything real; it's just guessing at best, and the results honestly look horrid to my eyes. The sensor shift tech was great - I've used it a few times in an Olympus body to produce high resolution raw files and it does the job quite nicely as long as the scene is still.

In terms of "sensor flare", I see this issue on the R1 with modern RF lenses including the RF 85L, 28-70 f/2, and even the RF 35 VCM. And sensor bloom where you get vertical flaring with mechanical shutter modes - which wasn't present on the 1DX II - is present on all RF bodies to date including the R1, R3 and R5 II (but oddly not on the 1DX III).

Back on the digital correction argument - Sigma just released a new 35mm f/1.4 DC DN II ART lens. This thing is almost perfect in terms of geometry, sharpness, CA control, is about the same size and is lighter than the 35L VCM. I would pay the same price as the Canon RF 35L VCM for that Sigma lens if there were an RF version. And you bet it performs better in terms of CA, sharpness etc than the RF 35L VCM.

I've said this before - if the RF VCM lenses were geometrically correct, I would have bought everything below the 50 (and probably the 50 as well - the 50 is however, geometrically appropriate). I actually cancelled my first-batch-in-the-country RF 35L pre-order after seeing the reviews, and affirmed my decision with an evaluation loan - but my EF II developed an issue that CPS were struggling to repair, so they offered me the replacement of either the EF II or the RF brand new - I should have gone for the EF, but I figured the increased contrast and size on the RF will be more practical in reality (but my photos are just not up to the same level of quality).

Perhaps there is a compromise on optical performance made to facilitate the use of the VCM AF system, or perhaps to allow for more economical repair or more resilient build quality to stand up to the rigours of professional use (something the Sony 35 GM absolutely fails at).

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The 2024 EOS R1 and 2024 EOS R5 Mark II do not use "Sensor Shift" (IBIS High Res) to create extra pixels. Instead they use a Neural Network Upscaling tool. This tool uses AI to predict and add pixels to a JPEG or HEIF file after it is taken. You are correct that this does not add "real" optical data. Instead it estimates detail based on deep-learning patterns.

The 2020 EOS R5 included sensor shift as a firmware update. This required taking 9 separate photos while moving the sensor. This method is now absent in newer RF bodies for three reasons:

Speed: High-speed stacked sensors in the R1 and R5 II are designed for 30–40 fps action. Multi-shot sensor shift requires the camera to be perfectly still for up to a second which limits its use for pros.

Processing: Upscaling is faster for the new DIGIC Accelerator processor to handle than merging 9 raw files into one 400MP image.

Heat: Constant sensor movement for high-res shots creates heat which conflicts with the thermal demands of 6K/8K video and high-speed bursts.

"Sensor flare" or "ghosting" happens when light reflects off the sensor and bounces back from the rear lens element. Modern RF lenses like the RF 85mm f/1.2L use Air Sphere Coating (ASC) to stop this. However you are correct that flare still exists in some mirrorless setups. Older EF glass like your 2007 EF 14mm f/2.8L II USM or 2006 EF 85mm f/1.2L II USM was coated for film or early digital. These coatings are less effective at handling the high reflectivity of modern "Stacked" sensors found in the R1.

The Sigma 35mm f/1.4 DG DN Art uses a large optical formula to correct distortion physically. The Canon RF 35mm f/1.4L VCM is designed to be a "Hybrid" lens. It prioritizes the Voice Coil Motor (VCM) for near-silent instant focus in video. To keep the lens small and the AF fast Canon uses digital correction to fix the extreme barrel distortion.

As you noted stretching these pixels in software causes a loss of raw detail in the corners.

On the 2022 EOS R7 this is less noticeable because the "crop" sensor ignores the lens corners. On the R1 or R5 II the "software stretch" is visible in large prints.


The EOS R1 reaches its maximum performance only with native RF glass. While the 2011 EF 400mm f/2.8L IS II USM and 2008 EF 200mm f/2L USM are optically excellent they use older 8-pin communication. The R1’s Dual Pixel Intelligent AF and 40 fps burst require the 12-pin speed of RF lenses to maintain "sticky" focus on fast subjects.

Non-sense: 1200mm is a "special" lens that sells close to zero. 400mm is a normal tele focal length.

dolina said:

The argument that digital correction compensates for sensor coverage fails to account for data loss. When a lens like my 2009 TS-E 17mm f/4L or 2008 EF 24mm f/1.4L II USM is adapted to the R1 or R5 Mark II the sensor records the native image circle. If a lens requires extreme digital stretching to fix vignetting or barrel distortion it effectively discards peripheral pixels. This lowers the actual resolved detail compared to a native RF design. For revenue-generating work this "software stretch" reduces the quality of large-scale prints.

The EOS R1 and R5 Mark II utilize advanced "In-Camera Upscaling" and Neural Network Processing. These tools work best with high-frequency data provided by modern RF glass. Older designs like the predecessors of the 2007 EF 14mm f/2.8L II USM and 2011 EF 8-15mm f/4L Fisheye were built for film or early digital sensors. Their glass coatings and internal baffles often cause "sensor flare" or internal reflections when used on the high-gloss surfaces of modern CMOS sensors.

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I've played with the in-camera upscaling as I feel like I was probably the only person on earth who used the IBIS-operated high resolution mode on the R5, and I've found that it adds detail that's not present in the original scene (even on the RF 85 1.2L). As with most AI-driven technology, you're not actually adding anything real; it's just guessing at best, and the results honestly look horrid to my eyes. The sensor shift tech was great - I've used it a few times in an Olympus body to produce high resolution raw files and it does the job quite nicely as long as the scene is still.

In terms of "sensor flare", I see this issue on the R1 with modern RF lenses including the RF 85L, 28-70 f/2, and even the RF 35 VCM. And sensor bloom where you get vertical flaring with mechanical shutter modes - which wasn't present on the 1DX II - is present on all RF bodies to date including the R1, R3 and R5 II (but oddly not on the 1DX III).

Back on the digital correction argument - Sigma just released a new 35mm f/1.4 DC DN II ART lens. This thing is almost perfect in terms of geometry, sharpness, CA control, is about the same size and is lighter than the 35L VCM. I would pay the same price as the Canon RF 35L VCM for that Sigma lens if there were an RF version. And you bet it performs better in terms of CA, sharpness etc than the RF 35L VCM.

I've said this before - if the RF VCM lenses were geometrically correct, I would have bought everything below the 50 (and probably the 50 as well - the 50 is however, geometrically appropriate). I actually cancelled my first-batch-in-the-country RF 35L pre-order after seeing the reviews, and affirmed my decision with an evaluation loan - but my EF II developed an issue that CPS were struggling to repair, so they offered me the replacement of either the EF II or the RF brand new - I should have gone for the EF, but I figured the increased contrast and size on the RF will be more practical in reality (but my photos are just not up to the same level of quality).

Perhaps there is a compromise on optical performance made to facilitate the use of the VCM AF system, or perhaps to allow for more economical repair or more resilient build quality to stand up to the rigours of professional use (something the Sony 35 GM absolutely fails at).

johnchio said:

Why don't they just slap an autofocus motor on and charge $1000 more? The people who will buy this lens probably would still spend the extra money. Or they could make 2 versions (one with and one without AF).

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The Zeiss Otus series are close to perfect ‘optically corrected’ lenses.

These have all metal tight tolerance construction. The resultant lens group mass precludes a practical implementation of either auto focus or image stabilization. IBIS only.

Also, the necessary movement required for image stabilization will slightly degrade the optical correction.

johnchio said:

Why don't they just slap an autofocus motor on and charge $1000 more? The people who will buy this lens probably would still spend the extra money. Or they could make 2 versions (one with and one without AF).

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Full-frame Canon 3rd party RF autofocus lenses? They would need a damned good lawyer!

johnchio said:

Why don't they just slap an autofocus motor on and charge $1000 more? The people who will buy this lens probably would still spend the extra money. Or they could make 2 versions (one with and one without AF).

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But then it would not be available for RF...

Richard CR said:

It's certainly a very niche lens without a doubt. The Sigma 35mm that was just announced in my mind is far more impressive.

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Well, that can be, but can I attach that 'impressive' new Sigma lens to my Canon camera? Maybe with superglue
The usual - Chinese - 3rd party manufacturers are focusing on the budget user, so there might be an attractive 'niche' for Zeiss.
And the MTF curves are looking impressive, especially for my focus on 'astro'. But that has to be proven with a real review.
The new Otus lens is increasing the limited selection of RF lenses which is always nice. With the Canon VCM 35/1.4, this new Otus 35/1.4 and a rumored Canon RF L 35/1.2 (?) lens, we would get a decent selection of fast 35mm lenses. And there are more 3rd party fast 35mm budget lenses.

Based on the available information, the new Sigma 35/1.4 lens is looking very attractive as it has AF, is lighter (500 versus 700g), cheaper (1200 EU versus 2400 EU) and also has impressive MTF curves, but that has to be confirmed by hands-on reviews. So Canons restrictive 3rd party politics is making the Otus look more attractive. Mmmmh ....

What size is the image circle?

After the 17-40 f1.8, was spected they start renewing the 16 and 56 primes.

Simple and perfect with beautiful sky in the background.

I would have expected the 16mm to become a 17mm, to center it between the 12mm and the 23mm. Maybe Sigma is rethinking their whole APS-C prime lineup, emphasizing their use in video. Does the 23mm become a 20mm and a 25mm? I do think they need a 40mm APS-C prime.

Why don't they just slap an autofocus motor on and charge $1000 more? The people who will buy this lens probably would still spend the extra money. Or they could make 2 versions (one with and one without AF).

It's certainly a very niche lens without a doubt. The Sigma 35mm that was just announced in my mind is far more impressive.

The latest 85 and 50mm Zeiss lenses weren't exactly overwhelming. And lack of AF didn't boost sales...
But a 35mm Apo sounds interesting, provided it is visibly better than Canon's VCM or EF 35mm f/1,4.
And, above all, if it doesn't cost more than the expected RF 35mm f/1,2 L AF. Otherwise, the Zeiss will be in a very precarious situation.

That was my beef with the 16mm. it was gigantic.