Jump to content
You must now use your email address to sign in [click for more info] ×

curves in/ out min/max


Recommended Posts

That without any contextual clues whatsoever, you are inviting a lot of silly replies, some of them NSFO?  :lol:

All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

Link to comment
Share on other sites

What curves dialog in what app & version?

All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

Link to comment
Share on other sites

I think it stretches or shrink the dynamic range, which say, for a 8bit image won't make magic.

 

 

  • Input minimum—specify, in float, a minimum value to use as tonal input.
  • Input maximum—specify, in float, a maximum value to use as tonal output.

 

From my understanding, it is similar to the output levels in PS, which I couldn't find in Affinity Photo levels:

 

levels.jpg

Andrew
-
Win10 x64 AMD Threadripper 1950x, 64GB, 512GB M.2 PCIe NVMe SSD + 2TB, dual GTX 1080ti
Dual Monitor Dell Ultra HD 4k P2715Q 27-Inch

Link to comment
Share on other sites

I think it stretches or shrink the dynamic range, which say, for a 8bit image won't make magic.

well bit depth does not actually have anything to do with dynamic range but with precision

 

apart from that I appreciate your input and will think about it

 

cheers 

 

 

@ RCR you should probably check out curves https://forum.affinity.serif.com/index.php?/topic/18992-understanding-curves/?p=88071 it´s the most powerful tool as it´s the most versatile, although it did not get much love in the 1.5 update cycle 

 

 

Link to comment
Share on other sites

well bit depth does not actually have anything to do with dynamic range but with precision

 

apart from that I appreciate your input and will think about it

 

cheers 

 

 

There's a relation, though: with higher bit depth you can technically store more information, hence a higher dynamic range.

Andrew
-
Win10 x64 AMD Threadripper 1950x, 64GB, 512GB M.2 PCIe NVMe SSD + 2TB, dual GTX 1080ti
Dual Monitor Dell Ultra HD 4k P2715Q 27-Inch

Link to comment
Share on other sites

  • 2 weeks later...

I think it stretches or shrink the dynamic range, which say, for a 8bit image won't make magic.

 

From my understanding, it is similar to the output levels in PS, which I couldn't find in Affinity Photo levels:

 

levels.jpg

well that does not make much sense in curves because this is basically just moving the curve points vertically (if you just move curve points horizontally, curves are equal to levels)

 

 

But I think I sort of figured the I/O thing out

It says "Input minimum/ maximum" and what that means, I think, is the range of the input.

Your image has a certain spread of whites and blacks which is defined as a fixed range.

And the I/O values set to 0 and 1 which is the default set their end points to just these values, so they cover the range of your normal image. (range is equivalent to dynamic range in some sense here, although that range is the same for every image in a given color space)

 

When you enlarge the difference between the I/O values to -100 I and 100 O then you spread the input range of the curves more, the range that is covered by your image stays the same though. 

You can see the effect by drawing a gradient and then modifying the curves.

You´ll se a much more drastic effect.

This is because a smaller movement now has greater effect because the range that your image covers, in comparison to the range the curves input range covers is very small so it is much like "zooming out" of the curves window. Your actual image now only covers a very small part of the curves dialog input range.

 

this part if still a bit half-baked:

If you modify only the I or only the O value (or both to a different extend) you will shift the balance between effecting the highlights versus the shadows.

If you keep the I at 0 but set the O to 10 your image covers less percentage of the right side/ of the whites and thus a smaller modification in this area will show greater effects than before.

 

If you lower your input minimum to say -5 then your blackest black of your image is mapped against a bigger value and thus becomes less black/ more grey

 

 

if you set I to the same value as O then you don´t map anything and your curves have no effect at all 

 

hope this is remotely correct and helps!

 

cheers 

 

 

Link to comment
Share on other sites

To experiment with this feature of the Curves adjustment, try the following:

 

Make a new document - 32bit. This gives you an unbounded (not constrained between 0 and 1) working document. Now, use the rectangle tool, or whatever, and make a box and then use the color chooser to make boxes with various exposures. I have made one for you - you can download the .aphoto file here:

 

https://www.dropbox.com/s/8l13orpca6xr8x1/Unbounded.afphoto?dl=0

 

The example file has a large rectangle that is 0EV and four rectangles below 0EV (-1, -2, -4, -8) and four above 0EV (+1, +2, +4, +8). In 32bit color, you can express these values in "intensity" (like log photographic exposure or stops) or in floating point (FP) values. Normally, a bounded working document has all values between 0 (black) and 1 (white). An unbounded document can have any intensity values - presumably even negative ones.

 

The 32bit document is linear, so doubling the FP value doubles the intensity, equivalent to increasing by 1 photographic stop, or EV. The Color Chooser in AP takes on a special form in a 32bit document, permitting you to choose "color" (RGB values) and intensity (in Stops). You can also dial in both using the FP values. The relationship between EV and FP values is:

 

FP Value = 2^(EV).

 

To visualize values beyond the display range, you can use the 32bit preview tool (Studio > 32bit preview). Slide the Exposure slider to adjust the range of values displayed in your 32 bit document. You will see that the current document shows you the rectangles that are in the range between 0 and 1. Dial in negative exposure and you will see the upper +EV rectangles appear.

 

In the document I provided, there is a curves adjustment layer at the top of the layer stack. You can use the min/max input values to specify what range of FP values you want to comprise the lower and upper bounds of your curves adjustment. Try setting the max input to 0.25 and pulling the white point node down to the horizontal axis (0 output). Notice that only the squares that have a FP value <=0.25 are affected. Etc.

 

This way you have a true 32bit curves adjustment that you can control the range of input values that get affected in 32bit mode.

 

Totally cool!

 

color-chooser.jpg

Link to comment
Share on other sites

This way you have a true 32bit curves adjustment that you can control the range of input values that get affected in 32bit mode.

 

Hm OK very cool, thank you so much for the detailed explanation! Much appreciated!

 

I somehow can´t find this fancy color chooser though 

 

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Terms of Use | Privacy Policy | Guidelines | We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.