Pink sky - why?

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Second photo - under-exposed with purple sky.

Could it be because I need to calibrate my monitor?

Thanks.

Jethro B-UK wrote:

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Could it be because I need to calibrate my monitor?

Thanks.

Absolutely nothing to do with the monitor, the sky is already pink on your "correct" photo.

And because most probably the color channels are saturated, when you bring the exposure down there is no info left there, so it just darkens the already pink sky, making it more visibly pink. You can see that the sky looks low-res and blocky, because there just wasn't any information left after the overexposure.

Also generally digital cameras do better shadow recovery than highlight recovery, so ETTR would be the preferred method to boost dynamic range of the image, but you have done the opposite of that. Expose the sky correctly, always shoot at base iso!!!, and then bring the rest of the image up.

And a further tip on your "correct exposure", the exposure is pretty wrong imo.

Shoot F8, after that diffraction starts to soften your image, on your APS-C camera.

Whenever possible please shoot base iso, especially on an older camera like that, if you want to do any post processing.

I don't see any part in your image that would have benefited from the 1/1000 shutter, 1/500 would have sufficed.

But what can you do to save the current photo? You can try the WB adjustment, and play around with "tint", the green-pink slider.

OrigamiCactus wrote:

Jethro B-UK wrote:

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Could it be because I need to calibrate my monitor?

Thanks.

Absolutely nothing to do with the monitor, the sky is already pink on your "correct" photo.

OK.

And because most probably the color channels are saturated, when you bring the exposure down there is no info left there, so it just darkens the already pink sky, making it more visibly pink. You can see that the sky looks low-res and blocky, because there just wasn't any information left after the overexposure.

Also generally digital cameras do better shadow recovery than highlight recovery, so ETTR would be the preferred method to boost dynamic range of the image, but you have done the opposite of that. Expose the sky correctly, always shoot at base iso!!!, and then bring the rest of the image up.

Thanks for the tip, will do.

And a further tip on your "correct exposure", the exposure is pretty wrong imo.

Shoot F8, after that diffraction starts to soften your image, on your APS-C camera.

I usually shoot at f/8 anyway.

Whenever possible please shoot base iso, especially on an older camera like that, if you want to do any post processing.

Of course.

I don't see any part in your image that would have benefited from the 1/1000 shutter, 1/500 would have sufficed.

I used a fast shutter speed to avoid blur with my 100-300mm telephoto.

But what can you do to save the current photo? You can try the WB adjustment, and play around with "tint", the green-pink slider.

Thanks for the tip.

Tom Axford wrote:

I suspect it may be a characteristic of your camera rather than your monitor.

Oh dear, I hope not.

The other possibility is that the sky was actually pink (or your white balance was incorrect), but that was not obvious when over exposed.

I have never noticed the sky turn pink with shots from my recent cameras (Olympus and Panasonic), but some older models sometimes showed colour casts in such circumstances.

What brand (s) was the older camera?

Here is an example in which I moved the Exposure slider in LR to -3.0. The sky is still the usual colour, although very dark.

sybersitizen wrote:

Jethro B-UK wrote:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Most of the pixel values in your original sky are not pure white. Some areas have more red, some have more blue.

Why? Is there a way to fix/avoid this?

Adjusting the 'exposure' (really just shifting pixel values) emphasizes those originally minor differences, making them much more prominent.

Right.

Could it be because I need to calibrate my monitor?

No, that's not the reason.

Good to know.

Jethro B-UK wrote:

OrigamiCactus wrote:

Jethro B-UK wrote:

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Could it be because I need to calibrate my monitor?

Thanks.

Absolutely nothing to do with the monitor, the sky is already pink on your "correct" photo.

OK.

And because most probably the color channels are saturated, when you bring the exposure down there is no info left there, so it just darkens the already pink sky, making it more visibly pink. You can see that the sky looks low-res and blocky, because there just wasn't any information left after the overexposure.

Also generally digital cameras do better shadow recovery than highlight recovery, so ETTR would be the preferred method to boost dynamic range of the image, but you have done the opposite of that. Expose the sky correctly, always shoot at base iso!!!, and then bring the rest of the image up.

Thanks for the tip, will do.

And a further tip on your "correct exposure", the exposure is pretty wrong imo.

Shoot F8, after that diffraction starts to soften your image, on your APS-C camera.

I usually shoot at f/8 anyway.

Whenever possible please shoot base iso, especially on an older camera like that, if you want to do any post processing.

Of course.

I don't see any part in your image that would have benefited from the 1/1000 shutter, 1/500 would have sufficed.

I used a fast shutter speed to avoid blur with my 100-300mm telephoto.

But what can you do to save the current photo? You can try the WB adjustment, and play around with "tint", the green-pink slider.

Thanks for the tip.

Ah okay, I take it that your 100-300mm is not stabilized?

In this case yeah, sometimes there is nothing you can do and 1/1000 is needed.

It is just that especially on older CMOS sensors, the dynamic range diminishes rapidly when deviating from base iso, especially on an old Canon made sensor.

But with ETTR at base iso you can get faster shutter speeds, because technically you are "underexposing", but you will bring the exposure back up in post for the underexposed parts, leaving the highlights as they are.

Even with a really old sensor, you should be able to get an image with decent dynamic range with this method, and if all else fails, you can always take multiple exposures and combine them into HDR.

Please could somebody see what they could do with the RAW file?

Here is the DxO linear DNG I used (dropbox):

https://www.dropbox.com/s/lx6o933dbakx2to/20220314-IMG_6303.dng?dl=0

(I've still got the original .CR2 file if needed.)

OrigamiCactus wrote:

Jethro B-UK wrote:

OrigamiCactus wrote:

Jethro B-UK wrote:

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Could it be because I need to calibrate my monitor?

Thanks.

Absolutely nothing to do with the monitor, the sky is already pink on your "correct" photo.

OK.

And because most probably the color channels are saturated, when you bring the exposure down there is no info left there, so it just darkens the already pink sky, making it more visibly pink. You can see that the sky looks low-res and blocky, because there just wasn't any information left after the overexposure.

Also generally digital cameras do better shadow recovery than highlight recovery, so ETTR would be the preferred method to boost dynamic range of the image, but you have done the opposite of that. Expose the sky correctly, always shoot at base iso!!!, and then bring the rest of the image up.

Thanks for the tip, will do.

And a further tip on your "correct exposure", the exposure is pretty wrong imo.

Shoot F8, after that diffraction starts to soften your image, on your APS-C camera.

I usually shoot at f/8 anyway.

Whenever possible please shoot base iso, especially on an older camera like that, if you want to do any post processing.

Of course.

I don't see any part in your image that would have benefited from the 1/1000 shutter, 1/500 would have sufficed.

I used a fast shutter speed to avoid blur with my 100-300mm telephoto.

But what can you do to save the current photo? You can try the WB adjustment, and play around with "tint", the green-pink slider.

Thanks for the tip.

Ah okay, I take it that your 100-300mm is not stabilized?

Correct.

In this case yeah, sometimes there is nothing you can do and 1/1000 is needed.

It is just that especially on older CMOS sensors, the dynamic range diminishes rapidly when deviating from base iso, especially on an old Canon made sensor.

But with ETTR at base iso you can get faster shutter speeds, because technically you are "underexposing", but you will bring the exposure back up in post for the underexposed parts, leaving the highlights as they are.

Even with a really old sensor, you should be able to get an image with decent dynamic range with this method, and if all else fails, you can always take multiple exposures and combine them into HDR.

tony field wrote:

Jethro B-UK wrote:

Could someone please explain this to me:

If I take a RAW file from my canon EOS 600d, and very under-expose it in software (LRc) the sky has a tendency to turn pink/purple - is this normal?

Below is an example. The first shot is the correct exposure (save for the sky), and the second is very underexposed. In the second photo (on my monitor at least) the sky turns partly purple after adjustment in LR.

First photo - correct exposure.

Second photo - under-exposed with purple sky.

Could it be because I need to calibrate my monitor?

Thanks.

The problem IMHO is that the picture was taken in hazy conditions which can cause colour variations depending upon what is causing the haze.

This isn't the first time I've noticed it.

Here is the requested .CR2 file:

https://www.dropbox.com/s/2otyueo0t56z0qh/IMG_6303.CR2?dl=0