What exactly is a Lut? I think I am getting old…

[Tulipone]

…you know when you read something and it seems to make no sense whatsoever? So I moved on and tried a simple guide and feel no closer than I was. Grateful if someone can explain in a few words - assume I am a complete idiot please.

They appear to be a preset designed to add an effect to an image. It seemed at one point that this could be uploaded directly to the camera with no further processing - but that sounds somewhat risky and unlikely - so a preset to be used with software - Photoshop?

I have no idea why I'm struggling!

 

[sirch]

A colour LUT is a Look Up Table which in its simplest form gives an output colour for an input colour. Taking an extreme example it may say red=blue so the software finds a red pixel looks it up in the table where red=blue and so the software makes that red pixel blue.

Obviously there are a lot of different reds, blues, greens etc so the table needs to specify specific hues and luminosities of each colour. An example might be trying to replicate the colours of an old colour film, no amount of playing with RGB sliders will replicate the look because the film simply didn't reproduce some shades so it is necessary to remove some shades by converting them to some other shade.

 

[garryknight]

Imagine that your post-processing software is looking at each pixel in your photo and getting a numerical value for its colour. It could then choose another colour value from a Look Up Table that it can use to recolour the pixel. It uses the original colour of the pixel to decide where in the table to get the new value from, using some mathematical formula. It then scans across all the pixels in your photo, replacing each of them with the colour value it gets from the Look Up table until it has converted the whole image.

That's basically it in a nutcase nutshell.

 

[Tulipone]

Okay thanks. Where / how do you do this?

 

[garryknight]

I use On1 Photo Raw and you can just import a load of LUTs and then apply one to the photo. The great thing about PR is that you open the LUT panel and it shows your photo how it would look with each of the LUTs. You can then just click one to have it applied.

I imagine that other programs have similar capabilities, though I haven't used any others for years now.

 

[Tulipone]

Thank you both. I think all is clearer.