Participant

Question

32bit levels not working - how to set black point and white point

Forum|Forum|2 years ago
April 15, 2023
2 replies
3399 views

Anyone know how to get levels to work in 32bit images.

Currently if I open a 32 bit HDR exr image and then go to levels (image>adjustments) to set the black point and white points it doesn't work.

Further, it shows 0-255 and I think that the range of the image should have significantly more range, so it seems like a bug - it's actually treating it like an image with lower bit depth.

I am aware that my monitor doesn't have the full range, I'm prepping an image to use as an HDRI for 3d render. I am also aware that since I don't have a "true" 32 bit white and black point that I am remapping onto the 32bit full range. I guess that is the point of the levels adjustment though. Or is levels broken for 32bit? Not sure if this is bug but definitely does not seem to be expected operation.

Thanks!

vers Photoshop 24.2.0

Mac Ventura 13.2

This topic has been closed for replies.

V

virtualhc

Participant

The way I've done it when producing HDRI images for 3D ligthting is to select the sun disc and then use the Exposure adjustment whcih is the only tool that I've foind in Phtoshop that would allow you to push the pixel brightness beyond the SDR range and as high as you want within the 32 bit range. On the other hand, I just came accross your post looking for a way of expanding the higher range of the whole sky, and masking it between tree leaves is not easy, particularly when several of the automatized selection tools in Photoshop simply don't work in 32 bits mode (e.g., the magic wand). I was looking for how I could use the Curves or other Image Adjustment tools to push the highlights beyond the SDR limit but from what I see in this thread it seems it's not really possible. I'll look into Affinity Photo or the other suggested editors. Have you found any good alternatives since you posted this?

kelvinproblem

Participating Frequently

Hi There,

Honestly I found some success using PhotoLine as @Wim5F94 suggested. It includes the referenced adjustment layer that allows manipulation of 32bit image data. That said, I only just got it to work for my use-case and I didn't feel like the method was very fluent. Also, I got excellent feedback from the people who wrote the program and they seemed to recognize this was a hole in adobe's support for an important image type. I recommend you give it a try.

Why adobe has levels for 32bit images but constrains it to 8bit range still bewilders me. Many, many people use HDRI images to illuminate 3d scenes and assets but adobe has basically said that this is a no-go as far as I can see.

I'd appreciate it in turn if you could post any successful directions you find. Good luck.

davescm

Community Expert

Levels does not allow you to map onto the entire 32 bit range it just maps within the range of the image.

You can map your image levels onto whichever part of the 32 bit range you choose using Exposure which offers a linear exposure adjustment along with offset and gamma.

As an aside I always prefer adjustment layers, rather than image>adjustments, as adjustment layers remain editable

Dave

H

helpwHDRAuthor

Participant

Hi Dave,

Thanks for your response here. It sounds as though you are saying it is not a bug, which is helpful.

But the histogram that levels provides at least shows info about what is in an image from the full dynamic range, right? That is the point of the histogram, isn't it? I guess I don't understand what you say here: "Levels does not allow you to map onto the entire 32 bit range it just maps within the range of the image." What does "maps within the range of the image" mean if not from the full dynamic range? I should say I do always work with adjustment layers.

I tried exposure as you said and it does provide the eyedroppers for black and white point but honestly I couldn't get it to work as you describe. If I, say, click on the sun as absolute white point with the white point dropper it does not seem to effect the full HDR range when I slide the 32-bit exposure to see what information is at the top and bottom of that range.

Can you give a bit more info about how to map the various parts of the 32 bit range as you say?

Though I should say, I only want to spec black points and white points at the end of that 32 bit range. And I don't want to judge as such, just spread it out, this is a frame from an HDR video and I plan on automating the full image sequence.

davescm

Community Expert

Hi Dave,

Thanks. Yes, that matches up with my experience making HDR images before. In a pinch I've made them with just 3 images but if I want to really represent the full dynamic range in a broad lighting circumstance I would go to 8, 10 or even more.

What I am trying to do here is to specify the white point and the black point already in an HDR image but map it to a wider (yes maybe the widest) range in the gamut of the provided range of the image format.

The levels, curves, and exposure tools are explicitly designed to "correct the tonal range and color balance of an image by adjusting intensity levels of image shadows, midtones, and highlights" as far as I can tell. This is what I am trying to do.

The tools are available. I recognize and mentioned that I was fully aware of the limitations of monitors (not to speak of paper) rendering a 32bit range.

I hear what you are saying about the dramatic, exponential potential of the full 32bit gamut but honestly isn't this translation of a visually difficult range the purpose of the graph form of the histogram itself? If the tool is given for 32 bit images, why doesn't it provide some indication of the range the format provides?

I appreciate your suggestion of the exposure tool from before but this doesn't seem to map image values in the 32bit space at all beyond what is given in the image. Can you tell me how to kick the white (the sun) up by several exposure factors? In a pinch this might work but I will want to automate it for a range of images in a sequence.

To say, when I was first taught to use photoshop back in 1991, the method was to shoot a bit flat and set your white and black points of the gamut to where the data is. This is all I want to do, but the image is already HDR but not sufficiently dark in darks or white in whites to be used to light a 3d scene. I have little or no concern about posterization or banding (and I'm not trying to create those effects as many do with curves, for example).

Thanks for any suggestions you have.

'The tools are available.'

They are not really as the tools were designed to assemble a set of linear. images on the 32 bit scale. We have the tools to map the other way i.e. 32 bit to the smaller 16/8bit but not expand to 32 bit without adding multiple image sets.

What you could do though, for your purposes in creating a high contrast HDR light, is add a set of luminosity based masks to duplicates of each image then clip an exposure adjustment layer to each and move the exposure of each in the 32 bit range. It will be stepped and would not be suitable for viewing but would give you some extreme contrast in for example the sun and sky compared to the land etc.

Dave

Sign up

To post, reply, or follow discussions, please sign in with your Adobe ID.

Sign in to Adobe Community

To post, reply, or follow discussions, please sign in with your Adobe ID.

Scanning file for viruses.

This file cannot be downloaded