Scopes

Switching scopes§

The three-way switcher under the scope area chooses which one is shown; your choice is remembered between sessions. Only the visible scope is computed, so leaving it on the one you use costs nothing. All three sample the live, fully-edited image and refresh a fraction of a second after you stop moving a slider.

Histogram§

The most familiar scope: a graph of how many pixels fall at each brightness level, from black on the left to white on the right, drawn per channel (red, green, blue) with overlaps blending. It tells you how much of each tone the image contains — but nothing about where in the frame those tones are.

• Piled up on the left — the image is dark, and shadows may be crushed to pure black (lost detail).
• Piled up on the right — bright, and highlights may be blown to pure white.
• Clipping warnings — a triangle lights in the top-left when shadows are being clipped and the top-right when highlights are; pull the relevant slider back to recover detail.

Vectorscope§

The vectorscope plots colour only, with brightness thrown away entirely. Every pixel is dropped onto the circle by its chroma — how colourful it is and in which hue direction. A black pixel, a grey pixel and a white pixel all land in exactly the same place: the centre.

Reading the circle

• Centre = neutral. Anything with no colour (R = G = B) sits dead centre. A black-and-white photo is just a dot in the middle.
• Distance from centre = saturation. The further a blob sits from the middle, the more vivid that colour. The outer ring is the limit a fully-saturated colour can reach.
• Angle around the circle = hue. Each direction is a different colour. Blobs are drawn in the actual colour of the pixels that landed there, so an orange cluster sits in the orange direction and is coloured orange — position and colour always agree.

The reference marks

• Six target boxes (red, magenta, blue, cyan, green, yellow) mark where those fully-saturated colours should land. Shoot a colour chart and its patches should sit near their boxes; drift reveals a colour cast.
• The dashed skin-tone line (running up and slightly left, at roughly the "123°" flesh-line angle) is the single most useful mark for portraits. Healthy skin of every ethnicity falls along this one line. If your subject's skin cluster sits off to one side of it, the white balance or tint is off — nudge Temperature and Tint until the skin blob settles back onto the line.

What you'd use it for

• Colour casts — if the whole cloud of points is pulled toward one hue, the whole image is tinted that way.
• Skin tone — line skin up on the flesh line, as above.
• Matching shots — two frames that should match should show a similar shape and position.
• Saturation — a tight blob near the centre is muted; points crowding the outer ring are near maximum saturation and at risk of looking artificial.

RGB Parade§

The parade is three waveforms side by side — Red, Green and Blue — that keep the horizontal position of the image. It's the best scope for exposure and, especially, for white balance.

Reading the three panels

• Left-to-right matches the photo. The left edge of each panel is the left edge of the frame; a bright lump on the left of the panels means the left side of the image is bright. This is the key difference from the histogram — the parade keeps where.
• Top-to-bottom is brightness of that channel, black at the bottom, white at the top. A trace pinned hard against the top edge is clipped (blown) in that channel; pinned against the bottom, crushed.
• Brighter in the scope = more pixels at that level in that column.

White balance by eye

This is the parade's superpower. Compare the heights of the three panels against each other:

• If red, green and blue sit at roughly the same level, the image is neutrally balanced.
• If red rides high and blue rides low, the image is warm (an orange cast).
• If blue rides high and red rides low, it's cool (a blue cast).

To neutralise a cast, adjust Temperature and Tint until the three panels line up at the same level for areas that should be grey or white — check the tops of the traces for highlights and the bottoms for shadows.

The three at a glance§

Scope	Shows	Best for
Histogram	How much of each tone and colour — no position.	Overall exposure; spotting clipping.
Parade	The same, but where in the frame, split by channel.	Per-channel exposure and white balance.
Vectorscope	Colour direction and intensity only — brightness discarded.	Colour casts, skin tone, saturation.

See also: Develop basics for the adjustment panels that move these scopes.