fp Horizontal green lines with ISO 6?

Started 3 months ago | Discussions
jma60 Regular Member • Posts: 125
fp Horizontal green lines with ISO 6?
1

The other day I was in a rush to to get some pictures taken for a presentation and did not have time to setup proper lighting, so I chose to use a long exposure with ISO 6.

I can't show the exact picture I used, but here's an example with similar exposure. showing the green lines

Note that the EXIF states the exposure is 30s, but the total ISO stacked exposure time was around 320s for this particular shot. I got this happening from 50s to 320s total stacked exposure time. However, I could only get exposures on the higher end to repeatably show the green lines, while exposures near 50s were sporadic, which leads me to believe this may be a thermal issue.

I also tried to replicate this with base ISO (100) but could not, probably because the max exposure time is 30s without stacking.

Has anyone experienced similar with their fp or stacked ISO exposures?

bizi clop
bizi clop Regular Member • Posts: 428
Re: fp Horizontal green lines with ISO 6?
2

I have no clue, just observing.

There are 14 sections divided by the green lines, which themselves appear to be 4 pixels high. From this horizontally compressed image, it's visible that they were created before the lens distortion correction:

Maybe you found some limitation of the readout circuitry, or maybe the camera chooses too long sub-exposures. It could worth contacting Sigma, maybe this information reaches the relevant engineer/programmer at Aizu…

BTW, what would've been the expected output? A perfectly white image (sans the darker smudge at the left)?  Does it happen when you try it in darker scenes or in complete darkness/keeping the lens cap on?

 bizi clop's gear list:bizi clop's gear list
Canon PowerShot G2 Sigma DP2 Merrill Canon PowerShot SX50 HS
OP jma60 Regular Member • Posts: 125
Re: fp Horizontal green lines with ISO 6?
2

Thanks for the deeper analysis, that rules out one suspect.

I was trying take a picture of a highly polished but dark-colored engineering component (think polished blued steel) against a white backdrop and was trying to avoid reflections/glare, but did not have time to setup any diffusers, so I actually took the picture (and the above example) in a very dimly lit room.

I just tried taking the following exposures:

  • ISO 6/320s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 6/320s/f3.2 with lens cap on
  • ISO 6/320s/f16 with lens cap on
  • ISO 6/500s/f16 in a well-lit room against a white wall, lens cap off
  • ISO 100/30s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 100/300s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 100/300s/f16 in a well-lit room against a white wall, lens cap off

Only the ISO 6/320s/f3.2/cap off exposure resulted in the same green line problem, so I'm inclined to think this is an exposure-dependent problem and not a thermal one. All the others resulted in a perfectly black or white image.

I've read about similar situations that have occurred with exposure of the sensor to lasers, but I really hope that this is a case of correlation-not-causation w.r.t sensor damage.

bizi clop
bizi clop Regular Member • Posts: 428
Re: fp Horizontal green lines with ISO 6?

jma60 wrote:

Thanks for the deeper analysis, that rules out one suspect.

I was trying take a picture of a highly polished but dark-colored engineering component (think polished blued steel) against a white backdrop and was trying to avoid reflections/glare, but did not have time to setup any diffusers, so I actually took the picture (and the above example) in a very dimly lit room.

I just tried taking the following exposures:

  • ISO 6/320s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 6/320s/f3.2 with lens cap on
  • ISO 6/320s/f16 with lens cap on
  • ISO 6/500s/f16 in a well-lit room against a white wall, lens cap off
  • ISO 100/30s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 100/300s/f3.2 in a well-lit room against a white wall, lens cap off
  • ISO 100/300s/f16 in a well-lit room against a white wall, lens cap off

Only the ISO 6/320s/f3.2/cap off exposure resulted in the same green line problem, so I'm inclined to think this is an exposure-dependent problem and not a thermal one. All the others resulted in a perfectly black or white image.

I've read about similar situations that have occurred with exposure of the sensor to lasers, but I really hope that this is a case of correlation-not-causation w.r.t sensor damage.

If it were laser damage it would be much more noticeable:

https://petapixel.com/2019/01/12/mans-1998-mirrorless-camera-fried-by-self-driving-car-laser/

https://petapixel.com/2019/03/09/this-2200-sony-camera-got-fried-by-a-tattoo-removal-laser/

Also the lines are too regularly spaced, so I guess it's a behaviour of the camera.

So is the bottom line that the lines only appear when the photo is already unsalvageably overexposed?

 bizi clop's gear list:bizi clop's gear list
Canon PowerShot G2 Sigma DP2 Merrill Canon PowerShot SX50 HS
OP jma60 Regular Member • Posts: 125
Re: fp Horizontal green lines with ISO 6?
1

bizi clop wrote:

If it were laser damage it would be much more noticeable:

https://petapixel.com/2019/01/12/mans-1998-mirrorless-camera-fried-by-self-driving-car-laser/

https://petapixel.com/2019/03/09/this-2200-sony-camera-got-fried-by-a-tattoo-removal-laser/

Also the lines are too regularly spaced, so I guess it's a behaviour of the camera.

I agree, hopefully there hasn't been any permanent damage to the pixels along those lines. I might do a test with an LCD screen to check the RGB values at each line once I have more time.

So is the bottom line that the lines only appear when the photo is already unsalvageably overexposed?

Almost, it seems the lines are guaranteed when there's overexposure, but there is still a chance of it occurring with a salvageable exposure. Below is the extracted JPEG from the original ISO 6/50s exposure with the important parts censored out.

I'll probably listen to your suggestion and contact Sigma about this, I just hope I don't get the standard "send your item in before we think about this" response I've encountered before.

jh3rd Forum Member • Posts: 93
Re: fp Horizontal green lines with ISO 6?

Isn't this just a case of LED lighting? I get bands (larger) with LED lighting (electronic shutter) I wonder if yhe the 6 iso just compresses these lines?

OP jma60 Regular Member • Posts: 125
Re: fp Horizontal green lines with ISO 6?
1

I don't think so, I wasn't using LED lighting in the original shot.  All the LED banding I've seen on my fp has been much smoother, with no color artifacts.  Though it's possible there is something going on with the stacking algorithm.

Keyboard shortcuts:
FForum MMy threads