7D 'Amp Glow' (was - Sensor Problems - Long Exposures)

Freester

Freester

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Mark
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Hi,

I have noticed a problem with my new (ish) camera and long exposures. Back in January I took the following image and noticed a light patch top middle:

(43s, f/22 ISO200 - RAW image imported into Lightroom and exported to JPEG, no tweaks)
IMG_9778.jpg


At the time I put it down to light leakage or a hot sensor. I had taken a few longish exposures before this one.

Tonight I went and had a little try out with my new Big Stopper 10 stop ND filters. This was the first image I took - literally I made 2 test shots (less than 1s) to judge my exposure and then exposed the following - again RAW image straight out of camera no tweaks...

(6mins at f/14, ISO100)
IMG_0714.jpg


Obviously after this long exposure the light patch is pretty obvious and I was a little disappointed.

To investigate further I made a couple of bulb shots out of the back of my house straight up at the night sky (excure the handheld street lamp shakiness!).

(70s at 14s, ISO 100)
IMG_0716.jpg


Same image as above but with +1 stop increase to show problem better
IMG_0716-3.jpg


106s at 16s ISO100
IMG_0719.jpg


I don't have a great deal of experience with this sort of length of exposure. Whatever the reason this isn't right, right? I've tried to take a few different shots at different times / locations and camera orientations but it's always middle right of the edge of the sensor on the shutter button side of the camera.

I should expect better than this at longer exposures yeh?
 
Do you cover the eye piece when you do long exposures, just wondering if light could be getting in through the viewfinder? Otherwise assuming the lens fits tightly no ideas, but would be interesing to hear whet the experts come up with :)
 
susie said:
Do you cover the eye piece when you do long exposures, just wondering if light could be getting in through the viewfinder? Otherwise assuming the lens fits tightly no ideas, but would be interesing to hear whet the experts come up with :)
Click to expand...


Hmmm. Good point. I don't. Having RTFM I thought covering the eye piece was just to stop the exposure meter getting upset :shrug:

Happy to be corrected though. In fact I may go and repeat one of these exposures now with said eyepiece attached :)
 
Yes, cover the viewfinder with long exposures. Light creeps around the mirror, some cameras are worse than others. Easy to check - set camera on Av, lens cap on, shine some light around the viewfinder area and press the release for as long as it takes. On my 40D I used to get a lovely sunset effect! New 5D2 seems better sealed though.

On you sample pics though, it looks like a combination of filter flare and sensor/filter reflections. I'm guessing you have a UV filter on - take it off and throw it away ;)
 
HoppyUK said:
On you sample pics though, it looks like a combination of filter flare and sensor/filter reflections. I'm guessing you have a UV filter on - take it off and throw it away ;)
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The top 2 pics have a mix of ND Grads and ND filters. The bottom 3 test shots have NO filters, not even a UV.

Will try again with the eyepiece cap fitted.
 
Nah it's not the eyepiece cap. I've taken in enough different locations / orientations . conditions to also not believe it's flare...

91s of f/16 at ISO200 with eyepiece fitted:
IMG_0721.jpg
 
Whatever the cause, the problem is some kind of internal reflection/flare coming from somewhere. Not sure which end of the camera it's coming from, or if something is happening inside the lens, but that's what it is. It cannot be anything else.

Try the lens cap shot with a torch shining into the viewfinder. Or outside on a bright day with the ten-stopper on, one shot with the viewfinder covered, and one without. And some test shots with and without filters, with a bright light source in the frame and a dark background. A sunset/sunrise or night street scene for example.

Why are you shooting at such high f/numbers? Not sure that's a problem, but it does promote the possibility of reflections off the aperture blades.
 
It's called a hotspot. I get them with my Canon 350D with long exposures. Post processing gets rid of it. Here's a guy that says he has same problem. Last photo on the page he talks about it. http://www.randallcipriano.com/blog/tag/infrared/
 
The one thing you haven't mentioned discounting is the lens? Were all these shots with the same lens, or different ones? If same, try the long exposure as above, but instead of lens cap, take lens off and use bodycap [or different lens] and cover eyepiece.
 
OK good call I will stick the body cap on and try again.
 
Right - 120s with viewfinder cover and body cover on (ISO200). Problem is the same. Surely this test rules out any issue with flare, lens or aperture?

IMG_0723.jpg
 
Is it possible you're having problems with the sensor heating-up?

I recall a few years ago, there was a Nikon with some weird effect that caused a red-colouring bands.

For the life of me, I can't recall what it was, where I saw it or how it was resolved.
 
I think Wail may be right - it looks just like the long exposure noise I used to get on my old D70. On the D70, it was caused by thermal heating of the sensor from the electronics located near to one edge of the sensor. The "glow" tends to be similar from shot-to-shot so creating a dark frame image like you have done in the test above and then subtracting that should help. I may be that as Matt says the long exposure noise reduction will do that for you. You need to find out if its a feature of the 7D design or whether there's something that Canon needs to look at on your camera.

Have a look on the web for people doing astro photography - you'll probably find lots of information about whether this is a feature of the 7D or whether it looks like you should get Canon to have a quick look at your camera.
 
Cheers people for helping to me to isolate the problem at least.

It was new in December. Will have a word where I got the camera as a first instance.

I've done some googling for this issue and not found anything. I find it surprising that it would be evident in a 60s exposure. Most of the images above were the first long exposure so it's not like repeated use for long stretches.

I'll try a shot with the long exposure NR turned on.
 
Freester said:
Right - 120s with viewfinder cover and body cover on (ISO200). Problem is the same. Surely this test rules out any issue with flare, lens or aperture?
Click to expand...

The Matt said:
Have you tried long exposure noise reduction? It may remove that for you.
Click to expand...

Ok repeated the 120s ISO200 test with Long Exposure NR turned on. Sorts the issue. Good.

Pain in the arse when doing Long Exposures though :(

Think I might have a word with Canon anyway to see if this is correct.
 
Aplogies Mark. I think we were talking at cross purposes. I can't see any noise on my screen and I thought you were looking at something else ;)
 
HoppyUK said:
Aplogies Mark. I think we were talking at cross purposes. I can't see any noise on my screen and I thought you were looking at something else ;)
Click to expand...

Eh? :thinking:
 
I think you are saying the image problem doesn't look like noise.

Well yes I agree. But it would appear to be something to do with perhaps thermal noise as the long exposure Noise Reduction sorts it out.

I am sure you were just joking but I didn't get the joke (I am a bit slow like that and need my missus to explain jokes to me sometimes!).
 
OK. I've done some research. This is what is known as 'Amp Glow' apparently. It is heat dependent - the astro togs have this problem.

I am just trying to work out whether this is normal with the 7D. Anyone else got this problem with long exposures on the 7D?
 
Freester said:
Ok repeated the 120s ISO200 test with Long Exposure NR turned on. Sorts the issue. Good.

Pain in the arse when doing Long Exposures though :(

Think I might have a word with Canon anyway to see if this is correct.
Click to expand...

I wouldn't expect it on a 7d. My 450 gives me no such problems. Hopefully you'll get a replacement or a repair from Canon. I'm glad the noise reduction sorts it though.
 
Freester said:
OK. I've done some research. This is what is known as 'Amp Glow' apparently. It is heat dependent - the astro togs have this problem.

I am just trying to work out whether this is normal with the 7D. Anyone else got this problem with long exposures on the 7D?
Click to expand...

Just tried it on my 7D, same settings as yours, 120sec body cap in place, long exposure NR off then on, and didn't see any glow on either images.
 
Les McLean said:
Just tried it on my 7D, same settings as yours, 120sec body cap in place, long exposure NR off then on, and didn't see any glow on either images.
Click to expand...

Cheers Les I really appreciate it. I was admiring your long exposures and was comptemplating PMing you to make the test. Just doing the same test on my 400D.

Gonna give my suppliers a call tomorrow. I don't think it's right.
 
And whaddya know? The 400D is fine.

Will get in touch about a return and keep you updated... :)
 
Freester said:
I think you are saying the image problem doesn't look like noise.

Well yes I agree. But it would appear to be something to do with perhaps thermal noise as the long exposure Noise Reduction sorts it out.

I am sure you were just joking but I didn't get the joke (I am a bit slow like that and need my missus to explain jokes to me sometimes!).
Click to expand...

I'm not joking! I can't see anything resembling noise. I can see other artifacts, which I thought you were referring to, that in the absence of other causes could only have some optical cause. It appears that we were talking about different things but whatever it is that I have been guessing at, the double image at the bottom your dark sky shot for example, it's not noise.

However, there have been some imaging problems with the 7D, sensors and processing related, that have been dealth with by Canon - sometimes by replacing the camera. Maybe this is what you are getting.
 
HoppyUK said:
I'm not joking! I can't see anything resembling noise. I can see other artifacts, which I thought you were referring to, that in the absence of other causes could only have some optical cause. It appears that we were talking about different things but whatever it is that I have been guessing at, the double image at the bottom your dark sky shot for example, it's not noise.

However, there have been some imaging problems with the 7D, sensors and processing related, that have been dealth with by Canon - sometimes by replacing the camera. Maybe this is what you are getting.
Click to expand...

Hi Hoppy. The problem is the discoloration in the middle of the top of the frame on the top 2 images. It is at the right of the frame in the dark test shots.

:)
 
Freester said:
Hi Hoppy. The problem is the discoloration in the middle of the top of the frame on the top 2 images. It is at the right of the frame in the dark test shots.

:)
Click to expand...

Sure, and given the tests that you have done with both the lens covered and the viewfinder also, it must be something that the camera is doing all by itself.

As I mentioned earlier, the 7D has had the odd strange sensor problem - a couple of people on here. I don't know the details but it's a return job.

Sorry for the confusion ;)
 
Freester said:
Hi Hoppy. The problem is the discoloration in the middle of the top of the frame on the top 2 images. It is at the right of the frame in the dark test shots.

:)
Click to expand...

Looks to me as if the camera was turned 'portrait' for the original shots and 'landscape' for the test shots - thus accounting for the 'glow' being in a different place when viewed.
The glow appears in the same place relative to the sensor.
 
Thanks for taking the time to comment.

I realise the problem is in the same place on the sensor. I think that's what I was trying to explain.

Anyway I spoke to the shop today. It's going back to them and then on to Canon for repair or replace.
 
Well an update. Contacted Park yesterday who told me they had got the camera back from Canon who had been unable to replicate the problem and so had just cleaned the camera up and reset to factory settings :bang:

Fair play to the guy at Park. I explained how to reproduce the problem (one minute exposure @ ISO 200 with the body cap on) and got a call later saying problem easily reproduced, he had had a word with the senior engineer at Canon as to why Park could reproduce the problem and yet Canon could not, and then Canon had picked the camera back up same day.

Hopefully they will sort it out quickly this time. :)
 
Well the camera is back and has exactly the same problem as before. Arrrggghh. Nothing fixed.

:bang:
 
Blimey that's really poor.
What's your next step, reject the camera as unfit for use?
 
Classic sensor noise pattern but reckon you've got it easy judging by my pic :lol:

Shot with a Nikon D80 this 30min single exposure shows serious issues. With the D80 the noise (amp glow, call it what you want) was not dramatically altered with long exposure noise reduction so I switched it off and saved hours. You can see how it affects three different sections of the frame - top corners when camera's in landscape mode and also about a third of the way between the corners.

The other thing about my D80 is that the noise got worse over the months. Whatever people say about shutter actuations it pales into insignificance against total exposure time. It's done only 18k actuations and the sensor is completely shagged with so much long exposure stuff. Initially amp glow was only obvious on exposures of 4-5 mins or longer but as the camera's been more and more (ab)used it's now really obvious after 1.5-2mins.

On that basis the 7D is only going to get worse so if you plan to do a lot of LE work I'd reject as unfit for purpose.

3588929270_282f727dcf.jpg
 
Well if Canon claim they can't replicate it and Park can i can only assume that this is known to Canon and they are fobbing it off in the same way Microsoft did with the 360 and Sont did with the PS3.
I would take it back to where you got it and demand a replacement or refund and make sure you post this issue on a many forums as you can.
 
Fair play to where I bought it from. Got an apologetic call from the manager today.

The camera is ready to be returned again tomorrow. The manager said if the camera is 'clean' he will just replace it. If it is marked then he needs to speak to his rep to agree a replacement. I worry though that he will just swap boxes / serial numbers and some other poor sucker will get my old body.

As far as I can tell it is 'clean'. But I have used it!

I had to laugh as I think the way Canon decided to 'fix' the problem was to turn on Long Exposure Noise Reduction. So the shop couldn't reproduce it as they put a card in straight away. My first shot was without card and so I spotted the problem on the display straight away as it displayed an realised it couldn't shoot the 'blank'.

Then I put card in and realised the camera was taking the 'blank' second 2 minute shot.


Arrgghhh.

It's just not right. I went out tonight and shot about an hours worth of long exposures with my 10 stop filter, 400D at exposure times of 2-6 minutes. Not an artefact in sight. My colleague at work did a 2 minute at ISO200 shot on a 7D with the body cap on no problem and another guy at work did the same test with an 20D. Jeez if the 20D and 400D don't do it why should the 7D. It's a shame I love that camera but if this carries on the dark side beckons.
 
Freester said:
Not an artefact in sight. My colleague at work did a 2 minute at ISO200 shot on a 7D with the body cap on no problem and another guy at work did the same test with an 20D. Jeez if the 20D and 400D don't do it why should the 7D. It's a shame I love that camera but if this carries on the dark side beckons.
Click to expand...

Sorry to read all the problems you've been having, does sound like you've just a bad copy to me, esp if a colleague did the same shot with his 7D as you did and had no problems.

If the manager is offering to do a swap for you, then try the new one out, before going to the extreeme of changing as i've read very glowing reports on the 7D, oh and that is good customer service :thumbs:

Hope you get it sorted out
 
Thanks for all the comments and support. I'm sure I just got a bad copy. I can't find any evidence of this being a common problem on t'internet.

Hopefully this will all get sorted quickly now. I went out and did some long exposures last night with my 400D. The solitude of Bat's Head and a beautiful evening was very therapeutic!
 
Freester said:
Thanks for all the comments and support. I'm sure I just got a bad copy. I can't find any evidence of this being a common problem on t'internet.
Click to expand...

That might be the case but how many people with a 7D are doing long exposures with a 10 stop?
My guess, not very many.
 
Freester said:
....

It's just not right. I went out tonight and shot about an hours worth of long exposures with my 10 stop filter, 400D at exposure times of 2-6 minutes. Not an artefact in sight. My colleague at work did a 2 minute at ISO200 shot on a 7D with the body cap on no problem and another guy at work did the same test with an 20D. Jeez if the 20D and 400D don't do it why should the 7D. It's a shame I love that camera but if this carries on the dark side beckons.
Click to expand...

I don't think Nikon's are immune to this problem, going by AndWhyNot's post!!!
 
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