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Question about 16bit images in Photoshop

Forum|Forum|7 years ago
July 22, 2018
4 replies
9899 views

I have heard that Photoshop only uses 15bits of image data for all values except the highest value, for which it uses 16 bits. This means, that instead of the range of pixel values going from 0 to 0xFFFF, they go from 0 to 0x8000. At least that was the way it was in very early versions of Photoshop, like Photoshop 7. Has that changed? Does Photoshop now allow true 16-bit image data to be retained, so that when I save a full 16-bit image, it doesn't lose half of its available values? If so, which version of Photoshop first introduced the handling of true 16-bit image data? If not, then that means that 16-bit image processing is lossy in Photoshop, and that is not a desirable trait.

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Correct answer davescm

Totally agreed. I have become a huge fan of Photoshop, but I also working in computer vision and am examining exact pixel values. This is a huge oversight and major dissapointment for the software.

15 bit +1 was not an oversight but a deliberate design in order to have an odd number of integers and therefore give a middle value. Chris Cox who was an engineer at Adobe explained, in the past, that this was to speed up many of the blending calculations. Whether that reason is still valid with modern PC hardware is a point for debate, although some still complain of lags. It is though still at the core of Photoshop.

For visual work it makes no noticeable difference as the difference between the two is well inside a difference that can be seen. In some work such as 3D heightmaps then it can make a difference - although 32 bit floating point linear can be used for such applications.

Dave

A

AllenY.NK

Participant

Here to support fellow 3D/VFX/game artists and computer science users. @rayek.elfin's concern and use cases are legit. Rayek's being professional and well-mannered (with some frustration), but many other so called profesional photographers/community experts were just failed to see the real points and keep bullying Rayek. If you don't have the usage and/or don't understand the use of full 16-bit range, doesn't mean it is not importand or not legit. Albeit you are a very experienced Photoshop user and long time member in the commnunity.

Photoshop started as a profesional photography software, but over the decades it is already grown into an image processor with much broader usage, well outside of field of photography. Many other users in the thread (like johnm42377455 & Alex25613730lde7) already pointed out the usage involved with the full 16-bit range. So, please look into those usage and understand them before you dismiss other people's point just because your own ignorance.

Height maps/normal Maps/computer science images all have legit and important uses of the full range of 16-bit. There are performance differences between 16-bit and 32-bit float and many industries have legit uses of 16-bit image files. Tell people to use other software if they need true 16-bit is just to overlook the importance of it. Plus, Adobe already acquired the Substance suite and integrated into their product line, also tries to make them all work together with other non-Substance products. It is more important than ever to understand and address the lack of true 16-bit mode.

davescm

Community Expert

I see no bullying here, nor would I call people ignorant.

What I do see is advice on how to make a feature request which will mean raising it under 'ideas' and outlining in detail use cases that would benefit from 16 bit integer but not be served by 32 bit float. Then getting sufficient votes to put it on the radar of Adobe's development team. This discussion thread is not such a request.

Dave

TheDigitalDog

Inspiring

I see no bullying here, nor would I call people ignorant.

What I do see is advice on how to make a feature request which will mean raising it under 'ideas' and outlining in detail use cases that would benefit from 16 bit integer but not be served by 32 bit float. Then getting sufficient votes to put it on the radar of Adobe's development team. This discussion thread is not such a request.

Dave

By @davescm

Exactly! Since no feature request exists here what we have is four years of a discussion going nowhere. Adobe engineering isn't paying attention and some wonder why. So again.

Start here:

https://community.adobe.com/t5/photoshop-ecosystem-ideas/how-do-i-write-a-feature-request/idi-p/1238...

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

S

SAMEOBAKE

Participant

As others have answered, I think the truth is that it is not that much of a concern in visible photography and video. Also, the production process in recent years often involves the use of floating point numbers.

On the other hand, if the values that need to be accurate are saved and used as images, it is also true that simply passing the software can degrade the image. I have encountered this problem several times in my work.

As a person who writes code, I understand that we made this specification at the time of development amidst performance and various other issues, and I do not expect Adobe to fix these issues.

I have tested other software and were able to find one that can process 16-bit images correctly, so we plan to move to that.

davescm

Community Expert

'if the values that need to be accurate are saved and used as images'

Can you describe your use case where retaining full 16 bit accuracy in images is needed and where 15 bit+1 makes a real world difference? Certainly not in photography which tends to start in camera as 14 bit raw data, so 15bit+1 is more than enough for adjustments. Display on screens is 10 bit at best, and 6 bit +dither at worst. Tests on printed output show no visible difference between 16 bit and 8 bit sent to printer.

I can think of one case in my workflow which is for 3D height maps. In that case I use 32 bit floating point.

Dave

D Fosse

Community Expert

This comes up with clockwork regularity, usually from people who make it a point to find "flaws" in Photoshop. Not one of them has ever demonstrated why this should have any practical significance whatsoever.

c.pfaffenbichler

Community Expert

Photoshop’s »16bit« is »15bit + 1«, so it is definitely not 15bit (as it cannot be expressed by just 15bit) but it does indeed not represent the 65536 values per channel one might expect but only 32769.

See posts by, for example, Chris Cox on the issue.

Re: 16-bit or 15-bit+1?

Why is there a difference in dithering quality when drawing in 8bpc vs 16bpc? | Photoshop Family Customer Community

As far as I know this has not changed so gar (CC2018).

If not, then that means that 16-bit image processing is lossy in Photoshop, and that is not a desirable trait.

And yet it can offer huge advantages compared to woking in 8bit depending on the image content and the Adjustment Layers’ severity.

I think there has been a Feature Request over at

Photoshop Family Customer Community

but I can’t find the pertinent thread at current.

rayek.elfin

Legend

Chris danced around the answer a bit when he was asked if the data in a full range 16bit image file is retained when opened in Photoshop. His answer:

Once inside Photoshop, the data is converted to the 0..32768 range. Yes, resaving will alter you data a little, assuming you had full 16 bit data to start with

"a little"? What kind of statement is that? The data is changed, or it is left intact.

Now, I agree that with RAW photography it might not be that important in most cases (arguably), but for VFX, film, HDRI and 3d work this may pose major problems down the pipeline. A 16bit full range image is not possible to create in Photoshop, and an existing one will be clipped from 65536 down to 32768 values.

For example, 3d rendered images may very well make use of the full range of values in order to use varying exposure values in a comp. Or a 2d artist may paint a background image in full 16bit range at varying exposures (Krita can do this very easily, for example) and using that same image in widely alternating lighting circumstances.

But Photoshop will clip the range of such images, making them unusable.

And Photoshop won't even warn the user about this. Absolutely unforgivable.

The main reason why Chris didn't implement the full 65536 range at the time when 16bpc was introduced in Photoshop for the first time was because of performance issues. At the time memory space and CPU speeds were a bottleneck, and that is the only reason why he and his team decided to implement a delimiter in Photoshop's 16bit image mode. And the fact that it is easier to calculate with, and less of a hassle for the programmers.

The real issue is that Photoshop's developers haven't fixed this as of yet. I assume they would have to tear out large chunks of older legacy code that affects the entire application by and large, and instead of running the risk of breaking everything, they just leave it as it is.

It's not even specifically mentioned in Photoshop's documentation, as far as I am aware. For example here:

Photoshop image essentials

In the meantime just about any other image editor and digital painting app supports a proper full range 16bpc image mode. And Photoshop "best in class" doesn't? Worse, doesn't warn users?

Sad, sad situation.

c.pfaffenbichler

Community Expert

an existing one will be clipped from 65536 down to 32768 values.

That seems to be a false statement, the number is 32769 (15bit + 1), not 32768 (15bit).

If one does not exist yet just post a Feature Request over at

Photoshop Family Customer Community

JohanElzenga

Community Expert

I don't know if that has changed, but do you honestly believe that there is any living soul on this planet who can see the difference between 15 bits color and 16 bits color (or any screen or printer that can display it)?

-- Johan W. Elzenga

D

donald newlands

Participating Frequently

Johan,

I am a living soul and I can see banding in my terrain model that is caused by this issue.
-Donald

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