Amp Glow 700d?

[Rico]

So I decided to give my new modded 700D a go last night (AA filter removed and Baader Filter replacing Canon Colour corrector). Clouds were teasing me the whole night so I wasn't able to get a good solid session. Nonetheless, I was able to test the camera. Very pleased overall. 

However, I did some darks and after stretching the image I noticed a consistent 'glow' from the right of the image. I've attached a jpeg of it ... heavily stretched. 

Is this normal? I never got this before with my unmodded 7D. (ISO 1600 - 400s) Lens cap on a 200mm f/2.8.

[Starflyer]

I've heard that some lenses make use of an internal IR led.  Try the test without the lens connected, if it goes away then that's your problem.

[Uplooker]

I would say that is amp glow.

Ian

[jgs001]

Were you using liveview to lift the mirror out of the way ?

[Rico]

I tried it without the lens and I still got the glow. I'd like to know if this is a common issue with the 700d. I tried it with the screen flipped away (switched off) and flipped to one side (timer shows up). The eyepiece was also covered. Anybody use a 700f here?

[Rico]

Anybody use a 700d?

[SkyGibbon]

I have a unmodded 700d and here is my dark with no lense, just cap, at 400s - 1600 ISO.

[sharkmelley]

That certainly looks like amp glow to me which is a bit of a worry.  SkyGibbon's dark also looks like it has glow in the same place (when it is stretched).

One thing to consider - do you switch the rear LCD off (using the DISP button) when imaging and when taking darks?  On other Canons  the heat generated by the LCD adds significantly to the thermal noise.

Mark

[SkyGibbon]

That certainly looks like amp glow to me which is a bit of a worry.  SkyGibbon's dark also looks like it has glow in the same place (when it is stretched).

One thing to consider - do you switch the rear LCD off (using the DISP button) when imaging and when taking darks?  On other Canons  the heat generated by the LCD adds significantly to the thermal noise.

Mark

My lcd was on and viewfinder was not covered. I don't use mine for AP, but wanted to give Rico another dark to look at. Now, you have made me want to run some more tests though, because maybe one day I will try some AP with it.

[Rico]

SkyGibbon ... I really appreciate this! Is there any way you can stretch the image on a single dark frame image. So open up the levels adjustment in PS and drag the white point marker all the way to the left? That should make it easier to see if there's any amp glow. 

Thanks!!

[Alien 13]

Is the glow on the same side as the battery could be a heating effect?

Alan

[Rico]

It's on the opposite side Alan (assuming that the image isn't reversed when it hits the sensor... just trying to figure out if this common to all 700d's or if it's just mine.

[Alien 13]

It's on the opposite side Alan (assuming that the image isn't reversed when it hits the sensor... just trying to figure out if this common to all 700d's or if it's just mine.

I did have a similar problem with my camera (battery on the right) but fixed it using a battery grip.

The image shouldnt be reversed but the top of the image will be the bottom of the sensor, that caught me out at 1st when i was looking for dust bunnies on the sensor.

Alan

[Rico]

Interesting Allen. If it turns out others have the same issue I may give that a go. It means having to buy a grip though! Lol

[sharkmelley]

If the amp glow is on the right hand side of the image, it means the heat is coming from the left hand side of the camera because up is down and left is right, if you see what I mean.  So no, it won't be the battery causing your problem because the battery is on the right (as you look at the camera from behind).  In any case, the battery is large (compared to the sensor size) so battery heat would not generate such a localised hot spot.

Mark

[SkyGibbon]

SkyGibbon ... I really appreciate this! Is there any way you can stretch the image on a single dark frame image. So open up the levels adjustment in PS and drag the white point marker all the way to the left? That should make it easier to see if there's any amp glow. 

Thanks!!

No problem. There you go. Sorry it took awhile, had left my house.

.

[sharkmelley]

Looking at the Gary Honis instructions for filter removal on the 650D/700D (http://dslrmodifications.com/650Dmod/650Dreinstallsteps1.html) there is a big black square integrated circuit on the back of the sensor circuit board in just the right place to give you that glow if that chip runs warm.  Look at step 10, within the square metal shield and just left of the orange ribbon cable.  Can't say for sure that is definitely the problem but I suggest the finger of suspicion points towards it.

Mark

[Rico]

I think you have the same amp glow sky gibbon. It isn't very prominent which may be down to the short sub. I've only had one session with my camera and tbh, it didn't prove to be too much of an issue with darks etc. Hopefully this won't cause any problems in the future.

Mark, it definately seems like it. It's a little frustrating as I had no amp glow whatsoever on my 7D. And I've heard nothing on amp glow on models newer than the 300D and 30D.

[wxsatuser]

No sign of it in my 60Da at any sub length.

[jgs001]

I don't see amp glow on my 450d or 60d, unless I've used live view to move the mirror box out the way (a pseudo mirror lockup), in which case the amp is on during the exposure. When I shoot without using liveview, the amp if off during the exposure.

[Rico]

If anybody with a 700d could post a 400 second dark sub (or more) that would be great (stretched levels to highlight noise). It would be good to have some more cases - to some amp glow might be a deal breaker when buying a new camera, to others it might not be.

Thanks guys

[SkyGibbon]

My shot was a 400 sec dark Rico

[Rico]

I know Skygigibbon, and I appreciate it ... just hoping for some more examples 

[sharkmelley]

An important point to realise is that shooting good video is increasingly becoming an important marketing point.  So sensor technology is being increasingly geared towards producing good video.  This tends to increase the amount of circuitry right next to the sensor.  Another effect is that sensor design is being compromised to accommodate a certain proportion of pixels whose main function is focus detection rather than light collection.  The purpose of this is to allow continuous auto-focusing when shooting video, which is clearly important for video users.  My understanding is that some kind of image interpolation must then be done at these pixel sites to mask the damage that would otherwise be done to the image.

Canon's CDAF auto-focusing with its focus detection pixels was introduced on the 650D and 700D (T4i and T5i) and there is an interesting Cloudy Nights thread here that discusses the impact on astro-imaging: http://www.cloudynights.com/topic/413422-examining-the-650dt4i-hybrid-cmos-af-pixels/   In summary when you perform a sigma stack (where outlying pixel values are rejected) some software (e.g. PixInsight) allows you to examine the rejected data.  A lot of rejected data falls exactly at those focus detection pixels because the in-camera interpolation can never be perfect.  In the end, if you dither your images you are not going to see any effect of those pixels in the final stacked image (since we have always performed similar processing for hot or dead pixels) but it is something to be aware of when processing data from these new cameras and it's an increasing trend to be aware of.

There are various online discussions about purple amp glow on the Canon 5D mk3 so it does seem that amp glow has once again become a hot topic [pun intended!].  But this thread is the first reference I have found to possible amp glow on the 700D.

Mark

[RichM63]

Tell me exactly what to do and I'll fire up my 700D for you, it is on the desk as I type. I've never done this before.