loss of contrast when lusing LUTs

[maxegb]

hello,everyone!

New user, here, and i have a question regarding luts (pardon me if it has already been answered. i did search for it but i had no luck) : when i finish to adjust a photo of a series i'd like to export a LUT that i can apply to the other pictures of the same set.

However,when i go to apply that LUT to the other pictures,i loose lot of contrast. does this happen to you as well? i am using the latest version on an m1 apple.

[Lee D]

@maxegb Even images from the same set may have some slight differences. Can you provide some side by side examples of the differences?

[maxegb]

yes, gladly.

these two images are the same raw file.

i did open and develop it (only adjustment in developing was sharpness). then :

1) added a black and white adjustment

2) added an exposure compensation

3) added a curve.

4) exported the first JPG

5) exported the LUT.

i then Closed the image, reopened the raw and re-developed it (identically)

1) loaded the lut saved in point 5 above, blend mode normal

2 ) exported the jpeg. 

look at the blacks: i cannot understand for my life why a cube generated by the same program could do this. 

i had the same issue with imported LUTs, but i thought that maybe it was because those were not "native"  (even though it made no sense, a .cube is a .cube. ), but like this?  I am really scratching my head...

Edited November 3, 2021 by maxegb

[maxegb]

just out of curiosity i downloaded the latest beta and the behaviour is the same. maybe just a little better..

[NotMyFault]

On 11/3/2021 at 5:39 PM, maxegb said:

yes, gladly.

these two images are the same raw file.

i did open and develop it (only adjustment in developing was sharpness). then :

1) added a black and white adjustment

2) added an exposure compensation

3) added a curve.

4) exported the first JPG

5) exported the LUT.

i then Closed the image, reopened the raw and re-developed it (identically)

1) loaded the lut saved in point 5 above, blend mode normal

2 ) exported the jpeg. 

look at the blacks: i cannot understand for my life why a cube generated by the same program could do this. 

i had the same issue with imported LUTs, but i thought that maybe it was because those were not "native"  (even though it made no sense, a .cube is a .cube. ), but like this?  I am really scratching my head...

 

 

Hi,

i would check the histogram for source (RAW) and edited image, especially as you mentioned exposure adjustment.

I wouldn't use exposure correction in Photo Persona (and LUTs) in the first place. If your images require adjustment on exposure, the risk of getting adverse effects is high, especially when using only RGB/8. The histogram could get extremely compressed, leading to banding and other artifacts.

The target for develop persona (to get good results) is normally to have a histogram using the full spectrum from black to white (and not cutting off on any side), and the click "apply" to do the fine tonal work in Photo Persona.

Main reason: in Develop (working on RAW images), you have 32bit color channel depth, and cameras are using about 12-14bits digital range. After pressing apply (to RGB/8), this gets compressed (or cut) to 8bits. You can't do the same level of exposure correction in 8bit, and will definitely loose quality. Especially in BW you have only 256 colors, and shouldn't reduce this range further. So may consider working in GRAY/16 (you are still able to export to jpeg RGB/8 if desired)

It would help to find the issue if you could upload the .afphoto file (saved with history). We would need to see all 3 stages (unedited RAW, first export, export after using LUT) to investigate further.

Did you watch the tutorial how to infer a LUT from source and edited versions of an image?

 

[maxegb]

here are  files i did without any exposure adjustment,the LUT, the two projects.

while i know how to infer a LUT, i think here we are not in "infer" territory. i do not need to reverse engineer an adjustment, i know exactly what has been done to the picture and i suppose i am saving it with the lut. or am i?

dscf1294.cube DSCF1294lutted.afphoto DSCF1294test.afphoto

[Lisbon]

Hi maxegb

I have downloaded your file (DSCF1294test.afphoto). The one that contains a curves and a B&W adjustment.
After exporting the LUT, just like you, i got a different result.

But if you look carefully at your curves adjustment you notice that there is no colorspace selected. Just an empty space.

This is important because when you export your lut, the curves adjustment will be ignored.
So you have to fix the curves. Reset the curves, set the color space to RGB and add the points.

At this point, if you export the lut you should get the same result.

[David in Яuislip]

1 hour ago, Lisbon said:

But if you look carefully at your curves adjustment you notice that there is no colorspace selected. Just an empty space.

Very good spot. I've just tried another 32bit image here and the curves layer is similar, doesn't show rgb

[maxegb]

1 hour ago, Lisbon said:

Hi maxegb

I have downloaded your file (DSCF1294test.afphoto). The one that contains a curves and a B&W adjustment.
After exporting the LUT, just like you, i got a different result.

But if you look carefully at your curves adjustment you notice that there is no colorspace selected. Just an empty space.

This is important because when you export your lut, the curves adjustment will be ignored.
So you have to fix the curves. Reset the curves, set the color space to RGB and add the points.

At this point, if you export the lut you should get the same result.

thank you, i will try.

But this opens a totally different can of worms, doesn't it?  I tried to retrace my steps back and it comes out that if you apply a curve to an image, the colour space of the default curve is empty when you click on it. it does not seem a correct behaviour...i won't call it a bug,but....

By the way,if you set the colorspace on the curve you cannot get back to the empty space. you loose the curve.

[Lisbon]

1 hour ago, David in Яuislip said:

I've just tried another 32bit image here and the curves layer is similar, doesn't show rgb

Another curious thing is that the result "without" colorspace is the same as RGB.
Maybe, when no colorspace is selected, it uses the current document colorspace.

1 hour ago, maxegb said:

I tried to retrace my steps back and it comes out that if you apply a curve to an image, the colour space of the default curve is empty when you click on it.

@David in Яuislipalso mentioned this but to be honest its the first time i noticed this behavior. I dont use 32 bit very often.

1 hour ago, maxegb said:

By the way,if you set the colorspace on the curve you cannot get back to the empty space. you loose the curve.

Yes. I pasted the values in notepad and added all again.
(Not practical, i know!)

1 hour ago, maxegb said:

thank you, i will try.

Your welcome.

[maxegb]

new weekend, back at it.

Apparently there is no relation between curves and loss of contrast. i did adjust a picture with no curve applied and the result is the same. Out of curiosity i told myself "maybe it's the exposure DSCF1389.afphotoadjustment that acts as a curve" so i switched it off and tried again...same result.

DSCF1389.afphoto

DSCF1389.afphoto desaturatebn.cube

[Lisbon]

Hi maxegb

Im getting a very different result from you.
After exporting the Lut the contrast was not affected but I lost exposure.

Since the lut didnt capture the exposure adjustment layer i replaced exposure with curves.

My curves adjustment settings.

At the end you will find my final LUT.
The LUT was exported at max quality (126x126x126).

maxegb, to export the LUT you went to File > Export LUT, right?

LUT_E.cube

[maxegb]

1 hour ago, Lisbon said:

 

maxegb, to export the LUT you went to File > Export LUT, right?

LUT_E.cube 51.51 MB · 0 downloads

yes,i did.

what system are you running?

[Lisbon]

Im using windows 10.
Also, if i go to View > Studio > 32-bit Preview im using this settings.

One thing I noticed was that my LUT is 51 MB and yours 179 KB. Certainly this difference must have some impact on the final result.

[maxegb]

would you like to guess what happens when i use your lut on my Apple? I am now downloading a copy of affinity for windows to see what happens....

 

[maxegb]

i tried on win10 and it works as it should. 

i am now assuming that either the whole mac version or the m1 flavor does something weird with the luts. is there a way to report a bug?

[Lisbon]

41 minutes ago, maxegb said:

i am now assuming that either the whole mac version or the m1 flavor does something weird with the luts.

I don't know if this is the case, but some issues can be fixed by changing the performance settings.
But I don't want to get into it. It's better to wait for someone more qualified.

42 minutes ago, maxegb said:

is there a way to report a bug?

Sometimes moderators move threads to reported bugs.
But there is also a section for this: Report a Bug in Affinity Photo

[Chris B]

Hey everyone,

I've reproduced this but I don't really have an explanation.

It is indeed correct on Windows for me and the steps I took.

I will feed this back to the developers.

[maxegb]

thank you!

[NotMyFault]

@maxegbdiscussing the technical issues i completely forget to say that i really like your photos. Excellent portraits. Great model.

[maxegb]

5 minutes ago, NotMyFault said:

@maxegbdiscussing the technical issues i completely forget to say that i really like your photos. Excellent portraits. Great model.

thank you very much!

[maxegb]

i got 10.5 and apparently the issue is still there. 

[Affinity Info Bot]

The issue "LUT does not apply the same effect after it has been exported" (REF: AFP-4767) has been fixed by the developers in build "2.1.0.1806".

This fix is in the current customer release.
If you still experience this problem once you are using that build version (or later) please reply to this thread including @Serif Info Bot to notify us