RF and EF extenders on the EF 600/4L IS II

Johnw

EOS R8
Oct 10, 2020
112
114
Nice writeup, I'm a fan of TCs when they can save you money. I can't afford any big white lenses at present so I'm using the Sigma EF TCs with the Samyang EF 135/2 adapted to the R bodies when I want larger apertures than the RF 100-400 has.

This is a relatively cheap setup that allows the following fast telephoto options.

135 2.0 - FF
189 2.8 - FF
216 2.0 - Crop
270 4.0 - FF
302 2.8 - Crop
432 4.0 - Crop
 
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Thanks for putting this together. I have all but the RF 2x, and I don't think I'll be in any hurry to get one now. It's interesting how the EF2x+RF1.4x preserves the line width of the text, while the EF1.4x+RF2x slims it down, so the former wins for me. I don't see any real benefit to going with the EF2x+RF2x over that (maybe a little less color aliasing, but I'll take double the shutter speed at that FL).

I have tested the RF 1.4x against the EF 1.4x III on the EF 600/4 II using MTF Mapper. I could not see any difference, except in the extreme corners the RF 1.4x was less sharp in my test. Across the rest of the frame, my 1200 dpi test chart was probably limiting.

BTW, I use the CommLite CM-EF-EOSR ARC adapter (with the control ring, but without the foot) because it only needs relatively minor surgery to fit the RF extender:

20220109-653A9903-3.jpg
 
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Johnw

EOS R8
Oct 10, 2020
112
114
I just ordered an RF 2x and one of the Commlite adapters to try this mod myself. This definitely increases the appeal of certain EF lenses, since EF are the only ones you can effectively double stack TCs without extension tubes using this method. For example, if this works for me I will probably pick up the Sigma 150-600 again. Having a 600-2400 lens sounds pretty good.
 
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AlanF

Desperately seeking birds
CR Pro
Aug 16, 2012
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22,838
I just ordered an RF 2x and one of the Commlite adapters to try this mod myself. This definitely increases the appeal of certain EF lenses, since EF are the only ones you can effectively double stack TCs without extension tubes using this method. For example, if this works for me I will probably pick up the Sigma 150-600 again. Having a 600-2400 lens sounds pretty good.
2400mm f/25 isn’t going to resolve significantly more than 1200mm f/12.6 by the time increased optical aberration and diffraction have kicked in, and will be horrible to handle. You would do just as well by buying Topaz Gigipixel and upresolving 2x.
 
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2400mm f/25 isn’t going to resolve significantly more than 1200mm f/12.6 by the time increased optical aberration and diffraction have kicked in, and will be horrible to handle. You would do just as well by buying Topaz Gigipixel and upresolving 2x.
Agree that 2400mm f/25 is not useful on a modern high-resolution body. You should consider that the 150-600mm zooms essentially have a 1.4x TC built-in to get from 400mm to 600mm, so just putting a TC on it is essentially stacking TCs (not exactly, but close enough to practical reality).

But I disagree that AI upscale with Topaz Gigipixel (or equivalent), is a panacea. Aside from the technical problems it can create, there are ethical issues as well. Unless the viewer expects the image to be artistically interpreted, then using AI in a photo that could reasonably be expected to be in documentary form is not kosher. But I don't mean to send this thread off in another direction, so I won't say more on that here.

Also, I didn't mention that the R5 can see both the EF & RF TC when stacked, and calls them both out in the EXIF, but it doesn't multiply the TC factors to get the total extension factor and effective focal length right. So that could affect AF and IBIS.
 
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AlanF

Desperately seeking birds
CR Pro
Aug 16, 2012
12,430
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Agree that 2400mm f/25 is not useful on a modern high-resolution body. You should consider that the 150-600mm zooms essentially have a 1.4x TC built-in to get from 400mm to 600mm, so just putting a TC on it is essentially stacking TCs (not exactly, but close enough to practical reality).

But I disagree that AI upscale with Topaz Gigipixel (or equivalent), is a panacea. Aside from the technical problems it can create, there are ethical issues as well. Unless the viewer expects the image to be artistically interpreted, then using AI in a photo that could reasonably be expected to be in documentary form is not kosher. But I don't mean to send this thread off in another direction, so I won't say more on that here.

Also, I didn't mention that the R5 can see both the EF & RF TC when stacked, and calls them both out in the EXIF, but it doesn't multiply the TC factors to get the total extension factor and effective focal length right. So that could affect AF and IBIS.
What I was getting at was that if you double up again the focal length of 150-600mm f/6.3 with a 2x TC on it already at 1200mm f/12.6, you increase the number of pixels by a factor of 4 but you hardly improve the resolution with a high resolution sensor and may even make it worse as TCs do degrade images to greater or lesser extents. So, you might just as well increase the number of pixels in post processing by using decent software like Topaz Gigapixel. I don't understand what you mean about ethical issues. Topaz Gigapixel doesn't do anything to alter the image artistically. All it does is to upresolve the image without making it softer. How is that unethical - it's no different from downresolving an image or sharpening it using software, and AI software does it better?
 
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What I was getting at was that if you double up again the focal length of 150-600mm f/6.3 with a 2x TC on it already at 1200mm f/12.6, you increase the number of pixels by a factor of 4 but you hardly improve the resolution with a high resolution sensor and may even make it worse as TCs do degrade images to greater or lesser extents. So, you might just as well increase the number of pixels in post processing by using decent software like Topaz Gigapixel. I don't understand what you mean about ethical issues. Topaz Gigapixel doesn't do anything to alter the image artistically. All it does is to upresolve the image without making it softer. How is that unethical - it's no different from downresolving an image or sharpening it using software, and AI software does it better?
AI doesn't up-resolve the image--that's not possible. The original scene micro-detail is irretrievably lost when it is down-sampled through the Bayer matrix filter on the sensor. AI takes cues from images in a training set, and applies them to the image to simulate a higher resolution, creating false (but believable) detail. It effectively creates a photo-composite, only at the pixel level. So if you use it on a photo with a bird as the primary subject, it will use feather detail from birds in its training set to produce feather detail that "looks" good. If your bird photo is presented as abstract art, that's fine. But if you are presenting the photo as an accurate representation of that bird in the wild, it's not. If that's too abstract, consider whether it would be ethical to use AI to up-resolve a crime scene photo used in court.
 
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AlanF

Desperately seeking birds
CR Pro
Aug 16, 2012
12,430
22,838
AI doesn't up-resolve the image--that's not possible. The original scene micro-detail is irretrievably lost when it is down-sampled through the Bayer matrix filter on the sensor. AI takes cues from images in a training set, and applies them to the image to simulate a higher resolution, creating false (but believable) detail. It effectively creates a photo-composite, only at the pixel level. So if you use it on a photo with a bird as the primary subject, it will use feather detail from birds in its training set to produce feather detail that "looks" good. If your bird photo is presented as abstract art, that's fine. But if you are presenting the photo as an accurate representation of that bird in the wild, it's not. If that's too abstract, consider whether it would be ethical to use AI to up-resolve a crime scene photo used in court.
What is your evidence that it is using training on a set of birds to create detail? Do you know what the neural networks are trained on? Are they just working from local general patterns? I can see in the patterns from the Topaz AI sharpening that they are doing a local geometric based sharpening and not reconstructing real feather detail.
 
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What is your evidence that it is using training on a set of birds to create detail? Do you know what the neural networks are trained on? Are they just working from local general patterns? I can see in the patterns from the Topaz AI sharpening that they are doing a local geometric based sharpening and not reconstructing real feather detail.
From the Topaz web site: "Gigapixel AI’s neural networks are continuously trained on a wide variety of sample images to understand how photorealistic detail looks. After learning from millions of images, our AI image upscaler can now believably increase resolution on a wide variety of different subjects..." There probably are some feathers in those millions of images. Also note that they say it's "believably" increasing resolution. That's telling.
 
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AlanF

Desperately seeking birds
CR Pro
Aug 16, 2012
12,430
22,838
From the Topaz web site: "Gigapixel AI’s neural networks are continuously trained on a wide variety of sample images to understand how photorealistic detail looks. After learning from millions of images, our AI image upscaler can now believably increase resolution on a wide variety of different subjects..." There probably are some feathers in those millions of images. Also note that they say it's "believably" increasing resolution. That's telling.
What AI is particularly good at is seeing patterns. If there are hidden patterns in interpolating pixels that it detects from say comparing low resolution images with high resolution then it can predict with some credence the best interpolation in various circumstances and not necessary using a database of say feathers. I think that Topaz doesn’t use accurate preset libraries of details as it makes a real mess of introducing artefacts when the settings are too high.
 
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Johnw

EOS R8
Oct 10, 2020
112
114
That's not a job for the fainthearted!

I used a manual file on mine but the job was pretty easy, took less than an hour. I also had to take off enough to expose the lower electronics so I covered that with a piece of tape to finish it off. I love this mod because now I can use the RF TCs with any EF lens, even ones that did not support TCs originally. With the ones that did, they can be double stacked.

2400mm f/25 isn’t going to resolve significantly more than 1200mm f/12.6 by the time increased optical aberration and diffraction have kicked in, and will be horrible to handle. You would do just as well by buying Topaz Gigipixel and upresolving 2x.

The utility would be limited of course. I'm mainly thinking of brightly lit astro targets like the moon or Venus, and using a tripod or equatorial mount. No hand holding at 2400. There is actually some decent close up footage of the moon at f/25 on youtube, mainly just lacking adequate stabilization to make it better.
 
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Jul 21, 2010
31,186
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I love this mod because now I can use the RF TCs with any EF lens, even ones that did not support TCs originally. With the ones that did, they can be double stacked.
On my list of things to try is the RF 1.4x behind the EF 85/1.4L IS for a 120mm f/2. That's really about the only non TC-compatible EF lens I still have worth putting a TC behind. Double-stacking might be fun with the MP-E 65, I don't see a need for it with the TS-E 17 or 24.
 
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