Marco Nero wrote:
NCamerin wrote:
Marco Nero wrote:
NCamerin wrote:
Kameratrollet wrote:
Different temperature what I found after a quick look. 15 vs 29 degrees C.
Not sure what you meant, that the temperature is the cause of the increment of white pixels?
We didn't have any problem until basicly 26th May where suddenly begining appear white pixels all over the frame and on Auguat 1st was worst.
Unfortunately, this issue of "stuck" and "hot" Pixels affects every model and every brand of camera. The solution is to do what everyone else does by using "Dark Frame Subtraction" when there are too many pixels to conveniently edit individually. I'd say quite a few of the stuck pixels on my EOS Ra are white with some being red, blue or green. If you see a white pixel with extremely dark (black) pixels surrounding it like a halo or a "cross" shape with the white pixel in the center, then it can sometimes indicate a pixel that is beyond stuck/hot and is closer to "permanently jammed" whilst not quite being truly dead. This may often not be repaired using the usual methods.
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To see if it's a serious issue or not, do the Sensor Clean with the lens OFF the camera and the body cap in place. Then try taking a picture using "normal" daylight exposures and ISO settings (eg 1/80 second with ISO 200 etc). Try to photograph something with a darker, smoother texture to make it easier to spot any errant pixels. If the pixels that appeared to be problematic in your long-exposure shots with high ISO settings are still visible in these tests, then you can be sure that there's an issue with the sensor. But it's unlikely.
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If those same pixels are showing up with normal daylight settings, you could contact Canon. It's possible they may or may not be able to assist because the EOS Ra is a limited edition camera and has only recently (2 months ago?) been discontinued (perfectly normal... it will probably be another 7+ years before another is released).
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It's normal to expect some (dozens?) of hot pixels to occur. Even with a new camera. My EOS 6D looked like it was snowing with over a THOUSAND mostly white pixels the first time I used it for Astro. The touchup took forever to clone them all out. A simple "manual sensor clean" using only the menu setting solved it and almost all of those white pixels vanished. The temperature in the air at the time can affect their appearance or disappearance. Cameras tend to generate stuck pixels on the sensor as time goes on and the camera gets older by several years. The hot pixels are simply not producing the color and tonal values expected. I'd say my EOS Ra produces around 20 or more (35?) hot pixels which often disappear when a so-called "Manual sensor clean" is applied. Remember you need to remove your lens and put your body cap onto the camera when doing this. If you leave the lens on when conducting this procedure, the results will be somewhat less effective.
Hi Marco Nero many thanks for your input and comment in this I do really appreciate as is the first time we deal with this kind of ''shower white' pixels behavior.
To be honest I'm/we are very surprised as I alredy wrote we have also the Canon EOS R and used it as astroimaging camera and we do not notice such increment of white pixels but we was ok with the usual hot and stuck pixels we used to see in the sessions with that camera.
Trully is with the EOS R we mostly used between 1-3 min exposure and ISO 1600-3200, while with the EOS Ra we normaly use between 4-8min exposure also between ISO 1600-3200.
My brother is testing the EOS Ra tonight in a Bortle 2-3 sky and alredy sent your sugestions of taking pics during day and cleaning sensor.
Again, many thanks for your attention and comment.
Best Regard
N Camerin
Hey there again! The process of the Manual Sensor Clean doesn't require you to manually touch the sensor. I probably should have mentioned this. I believe it's named this way because there are some physical actions taking place to try to displace any dust on the sensor. It also applies some type of static charge to the sensor that both repels tiny specks of debris and helps to unify the charge on the wafer that holds the pixel transistors. There's also some movement that takes place, presumably to tap the sensor and dislodge foreign objects (hence the clicking sound). Think of it like having one of those Etch-a-Sketch toys where you shake the thing to eliminate image that you were drawing, sort of like erasing the problem gently. There's even a mention of stuck/dead pixels on the EOS R user manual (Page 30 - under handling precautions). Canon deem that "this is not a malfunction" and that "they do not affect the images recorded" (!?).
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But something I forgot to mention is that Canon can "remap" the sensor for you, regardless of how old a sensor is. This can often identify and "map out" the affected pixels that cannot be removed via other methods. There are different opinions on how this works but the first time I heard about this, Canon were telling the processor to "ignore" specific pixels on the sensor wafer using an X-Y method and then sampling the pixels on either side of the affected one to recreate a mixture of surrounding pixel image hues/tones to replace the one not responding. This is a form of interpolation. It effectively masks the pixels that don't respond properly. This method can be applied any time but it's better to wait until the problem becomes noticeable or irritating first. If the camera with within a few years of age, Canon will usually do this for free if you send a strongly worded letter with the camera.
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Finally, Page 392 of the EOS R user manual (supplied with the EOS Ra) mentions Cosmic Rays. These can cause dots of light to appear in images. The manual suggests that selecting "Clean Now" may suppress their appearance
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This is something few people talk about and they can (and do) affect individual pixels on camera sensors. Cosmic rays can sometimes penetrate the atmosphere and travel more than 5km below the surface of the Earth. When passing through a camera body they can potentially kill a pixel transistor due to the tiny size but more commonly they don't... they just result in a tiny spot of light in an image. Certain types of radiation from radioactive minerals can hypothetically do the same. I might add that I have Tritium and Uranium samples directly below my camera storage cabinet so those haven't proven problematic to my sensors yet, even after decades of exposure.
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IMPORTANT: Only clean the sensor manually when there's a fairly good charge in the battery. Doing this with a nearly expired battery could cause the camera to freeze during the process. The Manual (page 393) makes a mention of using a fully charged battery when doing this.
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Since I'm unfortunately stuck in the Sydney Covid Lockdown at the moment, I can't get out with my EOS Ra right now. But I will report back in when I use it next if I notice any new stuck pixels. All the best!
Hi Marco,
I forgot to tell you as I'm in 'charge' of the imaging procesing, I do calibrate the frames with darks, flats and bias. Using a Newton scope and a fullframe camera the usual vigneting issue is a bit more evident but we deal with it and is not a problem.
As I have to come trought all the frames for select which one is ok for get calibrated and stacked I have to ´learn' how are visually the hot and stuck pixels and indeed some of them have alredy a secure 'spot' in the frame alredy. On regard the Cosmic Rays thanks a video I saw from Dylan O'Donell I can recognize now them on the frame too, thanksfully are so spare and dimm that did not cause a scrach pixel in the sensor atm (or that I'm aware off) jeje.
I hope that if is only a 'normal' white increment of pixels due to the usual heat for the large time exposure and elevate temperature because the summer time, and do not dismiss the quality of the image from the Canon Ra and could be then fixed with the usual calibration frame process.
Thank you for the advise in the Manual Sensor Cleaning and will take into account the 'remap' sensor possibility in the future.
Now I hope my brother could do the test today and in the night session and see the result that for sure I will report here.
I sent to him also your second comment.
Thanks a lot for your attention,
Clear Skies - Cieli Sereni
N Camerin
