Vignette and Colour Cast removal. How do I do that with HF3P?

PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast

I'd like to be able to remove some slight vignetting with a colour cast from a video. Apparently this is a common problem with a known solution. I just don't know which bits of HF3P to use to do it.

With a reference frame taken of a white surface the vignetting is visible.

Apparently,  the idea is to subtract this from the original video image to get back to a normal(ish) original.  But how do I go about this?

Comments

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador
    edited September 2015

    For the vignette white-frame, invert it and apply over your video in ADD blend mode. You might want to use Gamma, Curves or Levels (whichever you're more comfortable with) to adjust the vignette image so it works a bit better. 

    For removing a color cast, you have a whole lot of options. If your cast is simply too yellow or too blue, you could try a White Balance adjust. Otherwise, Color Balance, Color Wheels, Color Curves, Tint or Gamma can all be used to remove a color cast. The key is to be able to identify if the cast effects red, green or blue channels, and adjust appropriately. 

    Let's say it's too yellow. Yellow is made of red and green, therefore you need either less red and green or more blue: using White Balance I would raise the Kelvin to a higher value. With Color Balance or Wheels I would push sliders into the blues. With Gamma or Curves I would also raise the blue channels. For Tint, I would select a blue then turn the tint value down. 

    My personal preference would be Curves. There aren't any Hitfilm specific tutorials on color  correction with Curves, but if you look at tutorials for Photoshop or After Effects, well, it will be the exact same process in Hitfilm. 

    Sorry if this is a bit vague, but, as we see, this is one of those things that has several solutions. In fact, I haven't even listed all your options! Grade Transfer might be a good option. 

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast

    @Triem23 Thanks! I knew you'd have a solution (or three, or four)!

    However,  I'm stuck at the 'apply it over your video' stage in the first sentence. :(

    How, with what, where (in really simple terms)?

    General colour cast I can deal with, it's just the vignette isn't a simple grey, it is tinted slightly too (sorry if I wasn't clearer about that). The rest of the frame is fine. It's because the camera applies a colour profile/correction to the image using it's standard lens, but using a different lens the colour profile/correction isn't needed, but can't be turned off, and so needs to be uncorrected afterwards.

    I have the uncorrection plate, I have the video, but have no idea what effect/method to use that will allow me to 'apply it' in any mode.

    What instructions I have found on Add, Subtract, Multiply etc. are of the 'What': "you can use this to do..." type, when I need a bit more 'How':"use the dropdown menu for the source input on the doobry effect, which you'll apply above/below/sideways to your thingummy layer, then adjust the woozit slider for the amount of wiffle you require"

    I'm not expecting a tutorial, but if you could fill me on in a few little specifics, that would be great.

  • RobinRobin Website User, HitFilm Beta Tester Posts: 1,671 Enthusiast
    edited September 2015

    @Palacono in this case it just means putting the vignette layer over the video layer (so you have to normal video layers sitting on the composite shot timeline), and setting the blend mode of the top layer to add" by right-clicking the layer, choosing Blend Mode and then Add. Or you could set the Blend mode in the controls panel under the layer properties :)

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast

    @Robin  Aha! Holy smoke, I didn't even know there was a right-click-on-layer menu hiding there!

    I'm going to right click on everything I can find and see what other gems are hidden away. 

    Anyway, Invert the correction plate and Add blend works a treat! Thanks to all for the help (in more ways than one).

  • RobinRobin Website User, HitFilm Beta Tester Posts: 1,671 Enthusiast
    edited September 2015

    Glad it works for you, have fun enjoying your newly found right-clicking super power! I'm probably best gonna run for cover now.

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast

    I also had a play with the other modes, and Dodge gives similar results to Add, but I then expected that not inverting the Correction Plate and using Burn would give the same effect as Dodge, but it doesn't. I thought they were effectively opposites, but apparently not.

    I tried with the Correction plate Opacity at 50% as well to see if they'd meet in the middle, but they're still different. Oh well, what works works (Add) and that'll do for a while.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador
    edited September 2015

     

    My computers are out of service for the time being. I am smartphone only, so I am going to be more likely to suggest Google searches than full explanations and links for a bit. 

    Robin hooked you up on "How." Let me add some "Why."

    Ok, after this post, Google" Photoshop Blend Modes." Hitfilm's work exactly the same. 

    For now, remember a computer image is three or four channels (of data). Video is typically RGB--Red, Green, Blue. Each channel is 0-255 at 8bits/channel and 0-65535 at 16bits/channel. Some media  supports an Alpha channel--usually used for transparency. Each channel can be either thought of as a number from 0 to 1, or a grey scale image(black=0 white=1) with 0 being zero effect and 1 being full. 

    Ok, so... To simplify the Vignette a bit, let's pretend it's just luma without chromatic aberrations. Now we just have one chanel. Luma. We will treat it's values as 0-1.

    So, by shooting the white plate, you have a guide where the corners darken. Invert flips the channel values around the midpoint. 0 becomes 1. By inverting that image you now have brightening in the corners. 

    ADD mode adds the numeric value of the top layer to the lower layer. So... Let's say the source layer darkens at the corners by a value of 0.1. The inverted copy would be brighter by 0.1. -0.1+0.1=0. Cancellation. 

    Ok, so, quick primer on Curves, Levels and Gamma. Think of the curve as a graph plot of the values. X-axis is Input value from 0-1, Y-axis is Output value, 0-1. A diagonal line represents normal mapping. Adding points to the curve and dragging them around gives you visual feedback of how you are changing the values up and down. Curves lets you work on a master RGB curve or each individual channel. 

    Levels is simplied curves. You have two endpoints and a center point, but if graphically plotted, they would be straight segments, not curved. The sliders move 0, 0.5 and 1 around. 

    Gamma is also simplied Curves. In this case you basically have a fixed 0 and 1, and are just moving the middle point of a defined curve. 

    Hope this helps. I think it might help you understand other tutorials on curvrs and blend modes more easily. 

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast
    edited September 2015

    Great amount of information that'll obviously be helpful to others too, thanks for taking the time.

    I had Googled Dodge and Burn, which is why I was confused that they weren't working as opposites when using Invert/NotInvert on the Correction plate, but I suspect it's because it's not just Luma, it has Chroma too.

    Intrigued by what's at the end of the sentence that starts "We will treat it's values as

    Hmmm... on this page is shows that Photoshop has Linear Dodge (Add) and Colour Dodge.

    http://photoblogstop.com/photoshop/photoshop-blend-modes-explained#HowBlendModesWork

    Hitfilm has slight different names for things, but I'll work it out.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    Values were 0-1.corrected above. 

    Photoshop called them Add and Dodge until about version CS2, but, yes, you parsed Add and Dodge, more or less. 

    Burm in Hitfilm is a Color Burn. Linear Dodge is Subtract. No one knows why Adobe chose to stop calling them by the simple, accurate, "Add/Subtract," to go with the confusing "Linear Dodge/Burn."

  • Aladdin4dAladdin4d Moderator Website User, Imerge Beta Tester, HitFilm Beta Tester Posts: 2,509 Enthusiast
    edited September 2015

    Dodge lightens and Burn darkens so in that sense they are opposites but the operations won't produce opposite results for the most part.

    Linear dodge sums two layers. Blending with white gives white and blending with black produces no change. If the top layer is a single color the output black point is set to that color and the white input point is set to its inversion.

    Linear burn sums the layers and subtracts 1. This is the same as inverting both layers then summing and then inverting the result. Since it is "opposite" of dodge blending with white makes no change.

    Color dodge divides the bottom layer by the inverted top layer.

    Color burn inverts the bottom layer, divides by the top layer and then inverts the result

    And now my head hurts :) Wikipedia lists a lot of the math involved with different modes

    https://en.wikipedia.org/wiki/Blend_modes

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast
    edited September 2015

    Yikes! Thanks for that. I now need to lie down in a darkened room.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador
    edited September 2015

    Couple of years ago I wrote up a "math light" breakdown of Blend Modes in Hitfilm 2. Hitfilm 3 is the same, and I found the post, which I reproduce here: (Edit, note: I was told the post was 7500 characters too long! More changes in the forum than I thought! I am breaking things into three posts, starting... Now! 

    The Blend modes in Hitfilm can be found in the Layer Properties group in the Controls Panel for each Layer. 3D Particle Simulations can also composite particles in ADD mode.
    Before discussing Blend Modes, we should very quickly touch on how computers describe color. The three most common Color Models for video are RGB, HSL and LAB:
    RGB: separates a color into three primary components, Red, Green and Blue, and measures the level of Red, Green and Blue present. Most image and video formats are “8-bit” color, using 8-bits per color channel to give a range of 0-255. Higher-end formats might use 10-16 bits per pixel, thus providing a wider range of color detail.
    HSL: stands for “Hue, Saturation, and Lightness.”Hue represents the position of a color around the color wheel--Red is usually 0, Green would be 50% or 180 degrees. Saturation describes the intensity of a color--How much of a Hue is present. Lightness describes the luminance value of a color--it’s brightness from black to white. In an HSL model, the color of “Pink”is described as a low-Saturation, high-Lightness red-Hue, where a brown would be a high-Saturation, low-Lightness yellow-Hue.
    LAB: (Also known as Y/Cr/Cb) is a color mode that isn’t used in Hitfilm, but a basic understanding of the concept is useful. LAB mode separates a color into a “Luma”channel (containing all the brightness information) an “A”channel, which describes a color’s along a “Green-Magenta” axis, and a “B”channel, which describes a color along a “Yellow-Blue” axis. To better understand this, if you adjust the color on a television set, you can usually find Brightness and Contrast controls--These are affecting the “L-channel” The “Color Temperature”control is adjusting the “B-channel (yellow/blue)” and the “Color Phase” control is adjusting the “A-channel (green/magenta).”
    Blend Modes change the ways layers composite by performing mathematical calculations on pairs of layers. The bottom, background, Layer is the Base Layer, and the upper layer, the layer whose mode we are changing, is the Blend Layer. Blend Modes can be calculated using the RGB values for a pixel, the HSL value of a pixel, or“Standardized” to reduce each value to a decimal between 0 and 1. Most software reduces the RGB values to standardized levels before calculation, but any examples given below will assume 8-bit RGB, with values from 0-255.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    Before looking at each Blend Mode in detail, let’s do a quick summary:
    Add, Color Dodge, Divide, Lighten, and Screen, all brighten the overall image. In all of these modes, a Blend Color of black has no effect.
    Darken, Color Burn, Multiply, and Subtract all darken the overall image. In all of these modes a Blend Color of White has no effect.
    Hard Light, Overlay  and Soft Light all increase the contrast in the overall image.In all of these modes a Blend Color of 50% grey has no effect.
    Difference and Exclusion both invert luminance or color values in the overall image.
    Color, Hue, Lightness and Saturation all apply one or two of the three “HSL” components of the Blend Layer to the Base Layer.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    No effect is applied. The Blend Layer will completely obscure the Base Layer, unless the Blend Layer contains its own masking or alpha channel.
    Add: Takes the color value for each Blend pixel and adds it to the Base pixel below it. This results in a general brightening of the Base Layer. Add mode is useful for compositing bright elements into frames, such as fire, or explosions, however, with Add mode it’s very easy to clip color channels to their maximum values.
    Color: Combines Hue and Saturation values from the Blend Layer with the Luminance values of the Base Layer. This is often used to quickly tint images, by using the Blend Layer as a color map.
    Color Burn: This attempts to simulate “burning” film in a darkroom by increasing the contrast of the Base Layer based on the color values of the Blend Layer. Like “Multiply,”Color Burn darkens the overall image, but reduces highlights even more, and with more saturated mid-tones.
    Color Dodge: Basically the opposite process of Color Burn, this  simulates the effect of  “dodging” film in a darkroom  by decreasing the contrast of the Base Layer based on the color values present in the Blend Layer. Like “Screen” mode, Color Dodge lightens the overall image, but tends to result in intense, saturated mid-tones and blown-out highlights.
    Darken: For each pixel, Darken compares the color value of the Base Layer to that of the Blend Layer and displays whichever is darker. Darken can be useful for combining the black areas of multiple layers when attempting to create or refine masks.
    Difference: Takes the color value for each pixel, and subtracts the Base value from the Blend value. The difference between these values is used as the new color value for the pixel. If the resulting number is negative the positive equivalent value is applied (Example: “-64” would become “64”). If the Blend color is pure white (255,255,255), the Base color will be inverted. This effect can yield dramatic and psychedelic color shifts. The “Difference Key” effect is based off this blend mode--A clean “background plate” is used, and the identical areas in the footage to be keyed go completely to black, allowing the areas isolated by the Difference blending to be enhanced and separated into a luma key.
    Dissolve: For each pixel, the value is randomly picked from either the Base or Blend Layer. Some pixels will use the color data of the Base, and others will use the color data from the Blend. At 100% opacity of the layer, all pixels will take values from the Blend Layer. At 0% opacity, all pixels use Base values. At any value in between, pixels will be randomly chosen from the Base and Blend Layers. Dissolve doesn’t apply an kind of smoothing, blending, blurring or anti-aliasing, so the Dissolve Blend mode tends to look very grainy.
    Divide: One might think the “Divide” Blend  is the opposite of the “Multiply” Blend. However, this isn’t the case. (Screen is the opposite of Multiply) This Blend mode divides the Base value by the Blend value. Overall, this results in a lightening of the image.
    Exclusion: Similar to Difference, However, the calculation ignores positive/negative values, using absolute values only. This means similar values tend to get shifted to mid-greys rather than black, resulting in a lower contrast image. Unlike Difference, which can be used in keying, Exclusion is pretty much only useful for surreal, solarized color effects.
    Hard Light: Increases the contrast of an image by brightening any channel value greater than 50% and darkening any channel value less than 50%. Mathematically, Hard light uses a half-strength version of a “Linear Dodge”on brighter areas of the image, and a half-strength version of a “Linear Burn” on darker areas. Linear Dodge and Burn are not part of Hitfilm’s Blending modes.Hard Light is similar to Overlay and Soft Light, but more extreme than both.
    Hue: Combines the Luminance and Saturation values  of the Base Layer with the Hue of the Blend Layer. Used carefully, this can alter colors while retaining the tonal and saturation values of the image, which can result in accurate, subtle tonal shifts.
    Lighten: The opposite of Darken. Compares the values of the Base Layer and Blend Layer for each pixel, and uses whichever value is lightest for the final result. This can be useful when combining the white areas of multiple layers to create and refine masks.
    Luminosity: Takes the Hue and Saturation values from the Base Layer, and combines them with the Luminance values of the Blend Layer to generate the final color. Luminosity isn’t a very useful mode for creating artistic looks, but can be useful for sharpening. Try taking a layer, duplicating it over itself , converting it to greyscale and sharpening the living heck out of it. Then apply the Luminosity Blend Mode--you have now sharpened the bottom layer while avoiding the color halos and chromatic artifacts that sometimes appear with sharpening.
    Multiply: Multiplies the Base value by the Blend value, to determine the new value. (The new value is divided by 255, so the final value fits into the 0-255 color range.) Any color multiplied by black (0)creates black, and any color multiplied by white remains unchanged. Overall, Multiply darkens the overall image.
    Overlay: Increases overall contrast and vibrance of an image, in a manner similar to Hard Light and Soft Light. Values lighter than 50% have a “Screen”Blend applied, and areas darker than 50% have a “Multiply”Blend applied.
    Saturation: Takes the Luminance and Hue values from the Base Layer, and assigns them the Saturation values present in the Blend Layer. This can be used for artistic effects, just as selectively de-saturating parts of an image.
    Screen: Inverts the Base value by subtracting it from 255, inverts the Blend value in the same way, multiplies the result, then divides by 255, to bring the final values back within the 0-255 range. Screen is very similar to “Add”in appearance, but tends to be more subtle.
    Soft Light: Increases overall contrast and vibrance of an image, in a manner similar to Hard Light and Overlay. Values lighter than 50% have a half-strength “Screen”Blend applied, and areas darker than 50% have a half-strength“Multiply”Blend applied. The results are more subtle than Hard Light and Overlay.
    Subtraction: Subtracts the Blend Layer value from the Base Layer value, resulting in a darkening of the overall image. Negative values are clipped to 0 (black). Subtraction is the opposite of the “Add” blend mode.

  • RobinRobin Website User, HitFilm Beta Tester Posts: 1,671 Enthusiast

    Wow. Triem, you continue to be the superhero of this forum. Definitely going to bookmark this thread for these great and simple explanations.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    Thanks, @Robin. I realized I have an error in my explanations. In "Hard Light" I stated values over 50% are Linearly Dodged and values below 50% are Linearly Burned. I then said Hitfilm doesn't have Linear Dodge/Burn modes. That's the error. In Hitfilm Linear Dodge is Add, Linear Burn is Subtract. 

  • PalaconoPalacono Website User, HitFilm Beta Tester Posts: 3,442 Enthusiast

    Yes, @Triem23 knows his stuff. And now I have to go lie down in an Subtracted Hard Light room (or something).

    You originally wrote that several years ago?

    I have to go and complain about Scopes still being AWOL again...

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    Um, October 2013. @MichaelJames started a thread to attempt to crowdsource the Hitfilm documentation. He started with a breakdown of some keying effects, I started with blend modes, but the thread kind of died. 

    Not so much of a writing job as an editing job. Took the very photoblog article you linked to, above, and the Wikipedia article on blend modes, copied those to word docs, cracked open one of my Photoshop books (probably "How to Cheat in Photoshop." Great book, and much if it also applies to Hitfilm), and tried to synthesize a decent explaination that wasn't too heavy on the numbers. Re-reading it today, I did alright, but I see areas where I could improve the explanation. Also, screenshots illustrating examples of the blends would really help. 

    I started some CGI stuff in the mid-80's, and have been Photoshop literate since the mid-90's, plus messing around with other software over the years, so I have a decent grasp of a lot of underlying principles, but sometimes my age shows. And with Hitfilm I am playing a certain amount of catch-up. I remember once going into this huge, five-paragraph breakdown on how to set up layers to create a Difference Matte, only for Axel to come back with, "or, use the Difference Matte effect." D'oh! 

    Anyways, this particular forum has tons of helpful people, so I just try to help when I can and remember when someone else gives a great tip. We all get better together, right? 

  • Aladdin4dAladdin4d Moderator Website User, Imerge Beta Tester, HitFilm Beta Tester Posts: 2,509 Enthusiast

    Just for the sake of adding examples this link explains the Photoshop modes with pics of each in action.

    http://www.myinkblog.com/an-explanation-of-photoshop-blend-modes/

  • BadWolfKnightBadWolfKnight Website User Posts: 23 Just Starting Out

    @Triem23 Your answers in this thread helped a lot. Thanks a lot.

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    @BadWolfKnight, always glad to hel--oh, good lord those were long, weren't they? ;-) 

  • BadWolfKnightBadWolfKnight Website User Posts: 23 Just Starting Out

    @Triem23 Not really. They were long enough to provide all info but short enough to be not boring. :D

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,280 Ambassador

    @BadWolfKnight, yeah, but I see the initial post was 7500 characters too long and I had to break it up! That's the only time I've exceeded max length on a post...

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