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Use the dynamics range in the RAW file to render out hair


Rene Czepluch

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Hey guys.
- I wan't to share with you a new tutorial i made tonight.

The Raw image contains a lot of data (Huge dynamics range) use the raw filter to explore this and use it to your advantage. THis might not be the perfect method for rendering hair - but’s its a valid and good one, and good to have in your disposal.


What do you think about thips tip?
Have a nice sunday.
 

ALB68

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An interesting method. Thanks for posting it.
 

Tom Mann

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It's a nice method to have in one's tool kit, and thanks for posting the tutorial.

However, IMHO, you have given it an incorrect and possibly misleading name. The technique you appearing to be sugesting is nothing more than generating a classic luminosity mask adjusted so that the most contrast in the mask occurs in the tonal range between the hair and its background.

Also, I see absolutely no need to suggest that this technique needs the full dynamic range of a raw file. In fact, if the part of the image in question is bright enough so that one can visually distinguish the hair from the background in a temporary, brightened version of the processed image, one certainly can use the image itself to create a suitable mask. Of course if the image happens to be 16 bits/channel, it will provide somewhat smoother transitions than an 8bpc image, but one doesn't need to suggest that the full dynamic range of raw data is needed.

Perhaps a better name for your tutorial might be "Using luminosity masks to extract complex objects from their backgrounds".

With respect to its utility, the major problem in general applicability of this technique is that if you set the point of maximum contrast for best separation of (say) hair from background in a darker part of the image, this will not be the best setting to extract hair from background in a better lit portion of the image.

What one needs to overcome this limitation is either:

(a) an adaptive technique such as used in some commercial masking / cutout software; or,

(b) temporarily but dramatically reducing the contrast of the image at the lowest spatial frequencies while retaining (or even enhancing) contrast at high spatial frequencies. This can be done, at least to some extent, in ACR by decreasing the clarity slider and compensating for this by increasing the sharpening sliders. The better way to do this is by using either do-it-yourself or commercial frequency separation techniques such as Topaz Detail.

In fact, the commercial masking software packages use several different algorithms to initially determine boundaries and continue existing boundaries. For example, in some areas, they may find that a luminosity based technique (such as discussed above) is best, whereas in other areas, they may determine that a hue-based discrimination technique is better and switch to that. Also, almost all of them are adaptive in the sense that they use local image properties to segment the image. For example, as they wind their way around a head trying to determine the best separation of hair from its background, they will automatically recognize where the background brightness or color changes and adapt to that.

HTH,

Tom M
 

IamSam

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Hello Rene and welcome. I like the fact that you offer yet another manner in which to utilize a long standing method that has been around awhile, though I agree with Tom that you have improperly named the technique.

Since Tom has covered the content of the tutorial, I would like to mention a few things about it's presentation. I felt that you were not as well as prepared as you should have been. You talk extremely fast and, at times, you did not use proper Photoshop terminology when describing what you were attempting to demonstrate. Your onscreen movement was fast and erratic and several times without explanation (2:50 you delete a layer mask, 4:58 merge all). There were several moments when you yourself became slightly confused at 1:24 - 1:52 - 2:31(erased?) - 2:53 - 3:11 - and at 3:08. There was some major confusion at 5:22, that should have been edited out. Major confusion again at 5:51. At 6:22 you say 'we can start to draw on the hair'........with what? How? If your confused your viewers will certainly be confused.

Your problem at 6:44 was an easy fix with the Dodge & Burn Tools used on the layer mask, you may have known this with a little more preparation.

Overall not a bad job. You just need to do your homework on the methods or techniques your wishing to present so that you know what to call them. Slow down, don't talk so fast! Prepare and structure your presentation and make a few practice runs. Explain each step that you demonstrate. Stay focused on the technique and don't jump off on tangents.

Good luck!
 

Rene Czepluch

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Guys thank you so much for the feedback!Guys thank you so much for the feedback! Really detailed and in depth. I am happy you took your time, and wrote it.

Now that you write it, IamSam - i must agree with you. I shouldn't be confused with photoshop terminology. More preparation.

And thanks for writing a bit about these different techniques - i didn't know that about frequency separation. But i am not trying to defend my tutorial, however i don’t understand why you think it’s an ordinary luminosity mask. I mean, yes the result will be a normal mask, but the data is extracted from an RAW image, and it’s dynamic range that holds these extra information, to create the luminosity mask. - Let me know your opinion on that.

And huge respect for feeding be so much constructive critic.

 

Tom Mann

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Glad you found the comments useful.

OP:: "... i don’t understand why you think it’s an ordinary luminosity mask. I mean, yes the result will be a normal mask, but the data is extracted from an RAW image, and it’s dynamic range that holds these extra information, to create the luminosity mask. - Let me know your opinion on that...."

The reason is simple: You can get the same effect from any normal JPG, TIF, or other image, as well from an image that has already gone through a raw converter. One doesn't need the raw image to work from. It's a more general technique than you suggest by your title, so why emphasize this. If you are working on an image with 16 bpc, the effects will be almost indistinguishable. If you are only using 8 bpc and the hair and background are both very similar dark tones, the mask you get from the rendered version will be a bit more crude than what you would get using 16 bpc or the raw data, but you're still making nothing more than a luminosity mask tailored to separation of two objects (ie, hair and local background) in the image.

HTH,

Tom

 

Rene Czepluch

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The reason is simple: You can get the same effect from any normal JPG, TIF, or other image, as well from an image that has already gone through a raw converter.
Tell me if i am wrong:
In my tutorial, i am using the image as a smart object, and i am holding a RAW object in photoshop. Therefore i can get the unprocessed data from camera sensor. The JPG wouldn’t hold the same dynamic range in the image file.. (example: The raw image could get some information from blown highlights, in the jpg you would not)

Do you see where i am going at?
I just can't agree that you can get the same data from a JPG as you can from a RAW image.

But thank you for the critic - i am not trying to defend myself, i want to have a knowledge-sharing debate.
 

Tom Mann

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Rene: "... i want to have a knowledge-sharing debate. ..."

Superb! Me, too!

Yes, of course you are correct that there is more information in a raw file than in a JPG or TIF. But the real question is does this extra information help significantly in the problem at hand, separation of hair from a background. What I have been saying is that the amount of improvement provided by making the luminosity mask using raw data vs making one using the image itself is minimal.

So, let's consider two situations. For the moment, let's only consider B&W images to avoid the complications / alternatives offered by color. In the first situation, say you have a nice JPG or TIF in which the hair is somewhere in the middle of the tonal range (eg, well lit blonds, redheads, light brown hair) and the brightness of its immediate background is also of reasonable brightness. So, to make a luminosity mask that will separate the two, one can use curves (or other tools) to exaggerate the difference between the hair and its immediate background. Sure, one may get a bit better mask if you have a 16 bpc (bit per channel) or raw file compared to an 8 bpc JPG, but the difference in quality of the mask is minimal unless the tonality difference between hair and background is very small, say, only a couple of levels out of 256. This is what I am defining as "the second situation".

In the case of small local tonality differences between the hair and the background, sure, the increased bit depth provided by having raw data available can in principle help in separating the two, but the point is that the end viewer would likely never be able to see such small differences. In addition, if the difference in tonality between hair and background is that small, often there will be much larger variations in brightness from one area of the image to another that will be much larger than the hypothetical couple of levels (out of 256) that we are trying to separate, so one really can't make use of the increased bit depth one gets with a raw file and simple processing technique such as you suggested in your tutorial. Instead one has to use one of the adaptive or other techniques (eg, a mask based on differences in hue, etc.) that I mentioned in my earlier email.

What do you think?

Tom

 

Rene Czepluch

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Rene: "... i want to have a knowledge-sharing debate. ..."

What do you think?


It's really awsome to read! - you know a lot about bit and iamge quailty - i gotta find more information about that myself..

" sure, the increased bit depth provided by having raw data available "
- The RAW file is more than just information from the bit, It's the unprocced image from the camera! So it holds contrast, dynamic range, white balance. So it's more than just the extra bit - It's all theese extra information the picture had, before it got "backed" intp a jpg.

"
So, to make a luminosity mask that will separate the two, one can use curves "
- Not with this method - You need to use the camera raw editor, with an actual raw image. Curves can't acces theese dynamic range data that a RAW object in a smart layer holds.

"
the mask is minimal unless the tonality difference between hair and background is very small,"
- Am i lost? Don't you mean very high? With more difference it should be easyer to differenciate..

Haha this is really getting technical.. Good debate Imo :)
Thank you for the critic !


 

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