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Canon RF 70-200 experience


TBeachkofsky

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TBeachkofsky

All,

 

I recently picked up the newer RF 70-200mm lens...the plan for this lens is predominantly full color photography with a UV/IR cut filter. I currently only have a Kolari UV/IR cut filter for it but I may obtain more UV/IR filters...not sure as I am happy with my other lenses/filter options for dedicated UV/IR photography currently.

 

Initial testing....I started to notice some issues at longer exposures/higher ISO while doing some night sky photography. The first photo was taken using a Yongnuo 50/1.8 for comparison (no problems with this lens!). In regards to the issues I am observing with the RF 70-200, I am not sure what is causing the purple haze/hot spot. I wish I had a non-modified Canon body to mount the lens on for comparison but no such luck. My concern here is that these issues are a result of the use of a camera body with a full spectrum converted sensor. I would appreciate any feedback from this group. Is this IR reflection or something else? It gets worse at higher ISO and longer exposure. This seems internal to the lens as it occurs with or without the lens cap on. It does not change if pictures are taken in a dark room and the viewfinder is covered (ie...I don't think this is external light leak, but maybe I am wrong). Aside from file conversion there was no other processing of these images. I have also reached out to Canon to see if they have any thoughts and will update this thread with their feedback.

 

Image_1572

Canon EOS RP (Full spectrum sensor conversion by Kolari Vision)

Canon Mount Adapter EF-EOS R

Yongnuo 50/1.8 prime lens

Kolari Vision Hot mirror (UV/IR cut) Filter

F9, ISO 100, 30min exposure

CR3 converted to DNG by Adobe DNG Converter

DNG Converted to (low quality) JPG by Adobe Lightroom Elements

------------------------------------------------------------------------------------------

Image_1622

Canon EOS RP (Full spectrum sensor conversion by Kolari Vision)

RF70-200 @70mm

Kolari Vision Hot mirror (UV/IR cut) Filter

F4.5, ISO 100, 30 second exposure

CR3 converted to DNG by Adobe DNG Converter

DNG Converted to (low quality) JPG by Adobe Lightroom Elements

*You can see a purple haze while taking a photo of the night sky

------------------------------------------------------------------------------------------

Image_1623

Canon EOS RP (Full spectrum sensor conversion by Kolari Vision)

RF70-200 @70mm

Kolari Vision Hot mirror (UV/IR cut) Filter

F2.8, ISO 100, 5 min exposure

CR3 converted to DNG by Adobe DNG Converter

DNG Converted to (low quality) JPG by Adobe Lightroom Elements

*You can see a purple haze while taking a photo of the night sky

------------------------------------------------------------------------------------------

Image_1624

Canon EOS RP (Full spectrum sensor conversion by Kolari Vision)

RF70-200 @100mm

Kolari Vision Hot mirror (UV/IR cut) Filter

F32, ISO 100, 5 min exposure

CR3 converted to DNG by Adobe DNG Converter

DNG Converted to (low quality) JPG by Adobe Lightroom Elements

*You can see a purple haze while taking a photo of the night sky, star trail visible.

------------------------------------------------------------------------------------------

Image_1626

Canon EOS RP (Full spectrum sensor conversion by Kolari Vision)

RF70-200 @70mm

Kolari Vision Hot mirror (UV/IR cut) Filter

F2.8, ISO 25600, 30 second exposure

CR3 converted to DNG by Adobe DNG Converter

DNG Converted to (low quality) JPG by Adobe Lightroom Elements

*Lens cap on-you can see a purple haze with white hotspot

post-247-0-14548400-1587481815.jpg

post-247-0-96300300-1587481828.jpg

post-247-0-22777800-1587481842.jpg

post-247-0-80176700-1587481852.jpg

post-247-0-65127100-1587481861.jpg

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Tom, just a quick thought, but could it be an internal led from the camera, reflecting off the rear element of the RF lens? Does the RF lens have a rear element close to the lens mount?
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TBeachkofsky

Tom, just a quick thought, but could it be an internal led from the camera, reflecting off the rear element of the RF lens? Does the RF lens have a rear element close to the lens mount?

 

I wondered about this too but I don't see any leds with the lens off. Also, in the tear down Kolari published online, I didn't see anything noted. Yes, the rear element is very close to the lens mount...much more so than the EF version.

 

https://kolarivision.com/the-canon-eos-rp-disassembly-and-teardown/

 

Lastly, I should mention changing the F-stop does not change this finding but zoom and focus both do. Higher zoom, worse problem, further focus, worse problem. At 70mm and close focus it nearly goes away. I would think this means something internal is reflecting off the elements somehow but the source and wavelength are unclear.

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I think there is some sort of internal LED monitor in the Canon cameras. Not sure when or how activated.

In the original Kolari test of the R camera it failed miserably in the IR shutter monitor test. But then later Kolari changed the results. You can see it in the comments:

https://kolarivision.com/canon-eos-r-infrared-photography-review/

 

I would ask Kolari if they know about internal monitoring and when that might kick in. Everything you have said points to that. Easiest solution would be to just use adapted EF lenses. That should give you enough space to avoid the issue. In the comments someone recommends an f4 lens.

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TBeachkofsky

I think there is some sort of internal LED monitor in the Canon cameras. Not sure when or how activated.

In the original Kolari test of the R camera it failed miserably in the IR shutter monitor test. But then later Kolari changed the results. You can see it in the comments:

https://kolarivision...ography-review/

 

I would ask Kolari if they know about internal monitoring and when that might kick in. Everything you have said points to that. Easiest solution would be to just use adapted EF lenses. That should give you enough space to avoid the issue. In the comments someone recommends an f4 lens.

 

I talked with Kolari and the Canon EOS team a couple times yesterday and they are both reviewing the same pics/video I posted above. Hopefully they will get back in touch soon but troubleshooting is touch for everyone d/t working from home and lack of resources/testing equipment. I will mention your comment to Kolari/Canon when we speak. I like your idea for an adapted EF lens. I might just have to rent/borrow a EF 70-200 and see if results are different.

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Tom, my guess would be that the LED is tucked in behind that front plate within the camera, then with the rear element of the lens being close to the sensor some of the light from the LED is bounced off from that and back to the sensor. If this is the case then it will probably only show up as a problem with certain lenses.

 

As you zoom the RF lens, does that rear element move, and if you look in through the rear element, can you see the internals move as you zoom or focus?

 

I have an adapter Sony A7III and was amazed to not have problems after modification. But I only use adapted lenses on it, so that may be why I'm not seeing IR LED related issues.

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If it has an electronic shutter setting, an internal IR shutter monitoring led would not be used.

On my full spectrum Panasonic Gx85, the focus assist led caused horrible glare during focusing, but of course it is off during the actual exposure. I disabled it in the menus so I could focus. However, sunlight ingress through or around the focus assist led might be an issue. Try covering it and see if that helps.

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TBeachkofsky

If it has an electronic shutter setting, an internal IR shutter monitoring led would not be used.

On my full spectrum Panasonic Gx85, the focus assist led caused horrible glare during focusing, but of course it is off during the actual exposure. I disabled it in the menus so I could focus. However, sunlight ingress through or around the focus assist led might be an issue. Try covering it and see if that helps.

 

I would assume that the focus assist led is off in manual focus mode, no? Is it on full time? Otherwise I don't think this would be it as this is a fixed/full time problem. Though happy to try anything to help trouble shoot.

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TBeachkofsky

Tom, my guess would be that the LED is tucked in behind that front plate within the camera, then with the rear element of the lens being close to the sensor some of the light from the LED is bounced off from that and back to the sensor. If this is the case then it will probably only show up as a problem with certain lenses.

 

As you zoom the RF lens, does that rear element move, and if you look in through the rear element, can you see the internals move as you zoom or focus?

 

I have an adapter Sony A7III and was amazed to not have problems after modification. But I only use adapted lenses on it, so that may be why I'm not seeing IR LED related issues.

.

 

Jonathan, yes the rear element does move (see attached photos). The problem is made worse when the rear element is advanced forward with zoom. Does this help? Also, when I increase the zoom I can see a little electronic ribbon (see pic). Do you think that could be putting off enough of an IR source to cause the problem? Also, I cannot see any changes to the lens looking through the rear element when adjusting focus, I assume it is electronic as is the aperture and only adjustable when it has an electronic connection. It would be great to how a powered ring to attach the lens to and repeat some of these tests and maybe image the ribbon in IR and see if it is putting off much of a signature. Any thoughts? Also, when Kolari took this EOS RP apart I didn't see a LED behind the plate you noted and they didn't mention it in their tear down either. With that said I am not a small electronics guy...I could probably be looking right at it and not even know it.

V2T6Rndm.jpg

WKGmWGHm.jpg

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Tom, just so I'm clear then, the fogging is worse when the rear element of the lens is further away from the sensor (you said it was worse when the rear element is advanced forward). Is that that right?

 

If that yellow/orange piece in the second image is just a electrical ribbon connector, then I'm struggling to see how that would put out IR that the camera would pick up.

 

The shutter monitors are quite small and often embedded into some plastic moulding - it wont look like a big 3mm or 5mm LED out by itself.

 

Just thinking about how to nail this down. Do you have some double sided tape, aluminium foil, and a spare body cap for the camera. If so can you line the inside of the body cap with Al foil, obviously making sure to keep it away from where any electrical contacts would be. Put it back on the body, and make some exposures in Manual with similar settings to where you saw the fogging. If the source is indeed within the camera, then putting a nice reflective surface inside the body cap should give it something to bounce off. Obviously only do this if you can be certain that none of the Al foil can get loose, otherwise it could be a very expensive experiment.

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TBeachkofsky

Tom, just so I'm clear then, the fogging is worse when the rear element of the lens is further away from the sensor (you said it was worse when the rear element is advanced forward). Is that that right?

 

If that yellow/orange piece in the second image is just a electrical ribbon connector, then I'm struggling to see how that would put out IR that the camera would pick up.

 

The shutter monitors are quite small and often embedded into some plastic moulding - it wont look like a big 3mm or 5mm LED out by itself.

 

Just thinking about how to nail this down. Do you have some double sided tape, aluminium foil, and a spare body cap for the camera. If so can you line the inside of the body cap with Al foil, obviously making sure to keep it away from where any electrical contacts would be. Put it back on the body, and make some exposures in Manual with similar settings to where you saw the fogging. If the source is indeed within the camera, then putting a nice reflective surface inside the body cap should give it something to bounce off. Obviously only do this if you can be certain that none of the Al foil can get loose, otherwise it could be a very expensive experiment.

 

As I increase zoom on the RF70-200, the rear element moves forward (further from the sensor) and the fogging/flare gets worse. This problem has only occured with the RF 70-200 lens. I have repeated testing with two other lenses (Yongnuo 50 and Nikon UV 105) and with the body cap on (no lens attached) and cannot reproduce this same findings. The idea about the electrical ribbon was just a thought.

 

I conducted the test you noted (see pic of body cap with Aluminum foil). 30 sec exposure, Max ISO

 

Z7gwovMm.jpg

 

....just a black screen was recorded. I was unable to reproduce the same problem noted with the RF 70-200. It seems like something in the RF70-200 lens has to be the cause, no?

 

Next possible step...I have a friend with an EOR R (not a RP) body that has not been modified. I might see if he has the same problem. If yes then would I be correct in thinking that something in the lens itself is creating visible light? If it doesn't happen then perhaps there is an IR light source in the lens for which his sensor doesn't pickup because it isn't modified.

 

Thoughts? Thank you for the help troubleshooting.

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It would be the first time that I have heard about a light leak from a light source inside a lenses. But with newer lenses having lights and display screens, not impossible.

I found these images from Ken Rockwell's site here:

https://www.kenrockwell.com/canon/eos-r/lenses/70-200mm-f28.htm

 

The back element has some odd coating that might be reflecting some internal camera monitor at specific distance. I don't see any status lights inside the lens.

post-188-0-02642800-1587887248.jpg

post-188-0-48643900-1587887258.jpg

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Tom, thanks for doing the silver foil test. To me that suggests that the IR led within the camera bouncing off the back of the lens is not the issue then. Which, as David says, leaves the worrying conclusion that it could be the lens that is the issue.

 

The optical sensors in that write up are interesting. The question then is do they use ambient light, or do they have their own IR source (there wont be a visible light source in the lens for obvious reasons).

 

Tom, I'd drop Lens Rentals a note, say you've read their article, tell them about what you experienced, and ask them about those optical sensors.

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TBeachkofsky

Fellas,

 

Thanks for the comments and recommendations. I sent a message to Lens Rentals and am hopeful for a response. I will update this thread when I get more info.

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TBeachkofsky
Small update...previously I noted aperture was not much of an issue, I was wrong. It doesn't make much of a difference at high ISO but if ISO is at 100 and exposure 30", max zoom, changing aperture does cause an affect....small aperture better (high F-stop), large aperture worse (low F-stop).
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TBeachkofsky
Kolari suggested I tape off the electrical contacts on the lens. I did this with scotch tape and the problem went away as did all of the electronically controlled functions of the lens (as expected). The lens isn’t usable in this configuration but this test points to the problem being in the lens and requiring power.
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So not the first time or last time I have been wrong.

Great news is your camera doesn't seem to have the leak or possible IR monitor problem.

 

Interesting news is you found a lens that does. Maybe should be used for visible only. I wonder what led is used to monitor with the optical sensor in the lens. It seems the back element blocks the light leak, but when extended forward, the light gets through.

 

Maybe this will solve your problem with the lens:

https://www.highpointscientific.com/astronomik-cls-ccd-canon-eos-r-xl-clip-filter-clsccd-eos-r-xl?utm_source=google&utm_medium=cse&utm_term=ASF-CLSCCD-EOS-R-XL&gclid=CjwKCAjw4pT1BRBUEiwAm5QuR38OZwU3ekKm81rcTTauiidk8pOJdNNtmIjJ40AroPKRpeZ_sDR3XRoC86kQAvD_BwE

 

Or a similar clip in filter solution.

Or ask Canon if out of specification and get the lens led monitor replaced with a higher IR wavelength one, like what Jonathan has in his A7m3 to allow for its full spectrum conversion.

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David, just to clarify, I've not had the internal IR LED in my Sony A7III converted it is still the original one. I was told it may be a problem, but so far its been fine. Makes me wonder whether other lenses have these types of sensors.
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TBeachkofsky

Heard back from Roger at Lens Rentals... "that cut off on the right edge of the flare is something artificial. I'm sure there's a light source in the lens. I can't think of anything other than the optical read LEDs . There's another one under the focus ring, and actually I could see that leaking back into the barrel, it's s recessed into a barrel cut out. New fast horse in the race. In theory, you could possibly put some black tape under that one from inside the barrel."

 

Also heard from Kolari regarding the potential use of the Astronomik UV/IR cut filters that press into the body.

https://www.highpointscientific.com/telescope-accessories/astro-photography/filters/astronomik-l-1-uv-ir-blocking-filter-canon-eos-r-xl-clip-l1-eos-r-xl

 

...”It will help, but these types of filters typically only reduce that signal by 99-99.9%. That's a lot, but on a logarithmic scale that exposures work off of, you can typically still see internal leaks. It should increase your leak free zone by 6-9 stops though.”

 

Kolari also noted that their original testing was done with the EOS R kit lens (not sure which one) but now they test with EF glass. It is possible the original light leak they described was similar to what I am seeing here with the RF 70-200. Also, Kolari is coming out with a filter kit for the EOS R that will work with the drop in filter adapter EF to EOS R...that will be cool! With that said I haven’t really looked into the use of EF glass for IR work...if it is good, this might be a really nice setup.

 

I am waiting on a call back from High Point Scientific to get their opinion as well as Canon.

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  • 2 months later...
TBeachkofsky

Time to follow-up. So I eventually returned the RF70-200 and went back to the EF70-200. It appears this is a problem with a number of the RF lenses...maybe all of them so anyone looking to use them, beware.

 

The article below summarizes the problem pretty well with a number of examples from different RF lenses.

 

https://kolarivision.com/canon-mirrorless-rf-lens-internal-infrared-led-fact-or-fiction/

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  • 2 weeks later...
motorhead9999

Just to throw my two cents on your general situation:

 

My experience is that 9.5 times out of 10, modern lenses are not going to be good for IR work on a whole. I think the only native Sony lens I ever had that was excellent for IR work was the 55mm f1.8 Zeiss. But that's it. None of the Gmaster lenses were remotely usable. Granted, I'm speaking more about hotspots, but my point is that lenses are now becoming so complex (especially with IBIS and stabilization mechanisms) that more and more "features" are being baked into the lenses (either by mechanism, or by coatings) that it's almost a wash. I've had decent luck with some first gen EF red line lenses (the 24-105 f4 and 100-400), but they're also not perfect, but I'm willing to settle at this point. The best lens series I've seen (and given that you're doing astro/night work, will probably not be suitable for you) have been the Pentax K series, and Olympus OM lenses from the 70s/80s.

 

Again, just my two cents.

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  • 2 years later...

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