topic Re: Red Grain in the Under Exposed portions of the Image. Canon 70D in EOS DSLR & Mirrorless Cameras

Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Wed, 25 Sep 2019 13:53:49 GMT

With the majorit of the images I take, any section of the image that is slightly underexposed turns to the red grain as you can see on the bottom of the balconies in the image above. Is there a setting I can change or is it just what the Canon 70D does?

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Stephen — Wed, 25 Sep 2019 14:05:42 GMT

Hi, MatthewB!

Thanks for your post!

So the community can help you better, it might be helpful to have all of the EXIF information with your photo (the shooting details). Has your photo been altered in any way? If so, how? Which software (if any) do you use to post-process your images? Do you have the original file that you can share with the community? If your original file is too large to upload directly to the Forum, consider using OneDrive, DropBox, Google Drive, etc, but please ensure to allow public viewing only.

If you find that you'd like one-on-one help with your photos, don't hesitate to reach out to our friendly, US-based support team! They're available weekdays from 9am to 9pm (ET) and Saturdays from 9am to 7pm (ET). Support at Canon USA is free and is never outsourced.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Wed, 25 Sep 2019 14:11:38 GMT

https://drive.google.com/file/d/1x7gk4oLlLkn5K2Ul5T6-vD_SJrv9HyEV/view?usp=sharing

Does that allow you to see the full image with the photo data?

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

kvbarkley — Wed, 25 Sep 2019 14:43:40 GMT

Do you have the underexposure warning turned on?

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Wed, 25 Sep 2019 14:44:41 GMT

Possibly. Where in the settings could that be turned off?

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

ebiggs1 — Wed, 25 Sep 2019 15:10:06 GMT

Whenever you get unknown results and you don't know why, reset your camera. Menus under tools. You have set something and don't know what. Then you probably need to read your manual.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

kvbarkley — Wed, 25 Sep 2019 15:39:22 GMT

Sorry, you only have a highlight alert not an underexposure one.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Thu, 26 Sep 2019 01:12:50 GMT

@MatthewB wrote:
https://drive.google.com/file/d/1x7gk4oLlLkn5K2Ul5T6-vD_SJrv9HyEV/view?usp=sharing
Does that allow you to see the full image with the photo data?

1/80, f/7.1, ISO 100 : EOS 70D, EF-S 18-55mm f/3.5-5.6 IS II

The histogram is saturated in both highlights and shadows, especially the shadows.

The only time I have seen this type of noise has been in very underexposed astrophotography photos. Image data gets drowned out in sensor noise. I needed a longer shutter to capture more light. It is odd to see it like this, though, and so strong. I usually have to crank exposure up to like +5 Ev to see this type of noise.

Judging from the histogram, I suspect that this image has more dynamic range than the camera can handle. I would be curious to see the results of bracketing this shot as an HDR capture.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Thu, 26 Sep 2019 01:15:52 GMT

This seems to only happen when I'm shooting during the day with bright sulight and then the dark portions of the image become covered in the red grain. Does this make sense?

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Thu, 26 Sep 2019 01:18:59 GMT

I hope your sensor is not failing.

This is really not a whole lot of post processing. All I did was click [AUTO].

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Thu, 26 Sep 2019 01:20:29 GMT

@MatthewB wrote:
This seems to only happen when I'm shooting during the day with bright sulight and then the dark portions of the image become covered in the red grain. Does this make sense?

Yes, it does make sense. Was this shot in sunlight? It seems overcast.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Thu, 26 Sep 2019 01:23:21 GMT

It was bright sunlight with no clouds, I was standing in the shade.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Thu, 26 Sep 2019 01:43:44 GMT

@MatthewB wrote:
It was bright sunlight with no clouds, I was standing in the shade.

And, the building face is not in direct sunlight. The sky is totally washed out.

I think your shot just might have too much dynamic range. Are you familiar with HDR captures?

Here is one. Exposing for the background was too dim to capture the foreground. Exposing for the foreground was too bright for the background. I took three shots -2, 0, 2 Ev.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

MatthewB — Thu, 26 Sep 2019 01:45:27 GMT

I do know what they are but dont know how to take them in camera

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

ebiggs1 — Thu, 26 Sep 2019 20:00:56 GMT

The DR of that shot is not extreme. It is drastically underexposed. Try the shot again with a more correct exposure and see if it helps. But first reset your camera to default settings. Otherwise call Canon and schedule a C&C. Tell them the problem you are seeing.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

ebiggs1 — Thu, 26 Sep 2019 20:05:31 GMT

HDR, "..but dont know how to take them in camera"

Very simple and any camera can do it. Some cameras can do it automatically. Check your manual. Essentially you take three or more shots each with a slightly different exposure. For instance take a 1 stop underexposed, correct exposure and a 1 stop over exposed. I prefer to use Lightromm or Photoshop to merge the three, or more, shots together.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Peter — Fri, 27 Sep 2019 09:55:33 GMT

My guess is that 70D reads out 4 columns at a time and one of them is defect. Search for Weird stripes on 5D mark II raw. The sky has a maze pattern same as some 7D and 5D II. Green Equilibration in RawTherapee solves that.

Bayer pattern from your 70D below:

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Fri, 27 Sep 2019 14:51:34 GMT

The DR of that shot is not extreme. It is drastically underexposed.”

It is both under and over exposed. Look at the histogram. It is saturated in both highlights and shadows.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Peter — Fri, 27 Sep 2019 17:06:52 GMT

With Hraw it is easy to check the highlights. 0.001% clipped in green channels.

Re: Red Grain in the Under Exposed portions of the Image. Canon 70D

Waddizzle — Fri, 27 Sep 2019 22:57:31 GMT

@Peter wrote:
With Hraw it is easy to check the highlights. 0.001% clipped in green channels.

I think you are correct. I took a closer look at the histogram, and the highlights are not saturated.