Everything's black. How do I see it?
A linear frame is almost all near-black pixels with faint signal buried close to the floor. Every frame the viewer opens is already stretched for display, using a built-in default for its subtype, so you are never looking at raw linear values on screen. The Stretch block in the Interaction panel is where you adjust that look and, for lights, save it.
Screenshot: The Stretch widget in the viewer’s Interaction panel with the black point dragged in.
The widget
Section titled “The widget”The widget draws the frame’s histogram with the current transfer curve over it. Three handles sit on it. The two feet drag horizontally along the intensity axis, rightward to increase; the handle on the curve drags vertically. The readout beneath the widget states it as drag ↔ feet: black / white point · drag ↕ curve: faint lift.
- Black point (the blue foot at the baseline, at the dark end). Drag right to clip more of the shadow away; drag left to lift the noise floor into view. Reads as black in MAD units below the median.
- Stretch factor (the yellow dot on the curve, over the median). Drag up to brighten faint signal further; drag down to pull it back. Reads as stretch, a target background level.
- White point (the pale grip at the top of the axis, at the bright end). Drag right for more highlight headroom, which keeps star cores and bright nebulosity off pure white; drag left to bring the bright end in and raise contrast. Reads as white in MAD units above the median.
All three are relative to the frame’s own median and MAD, so the same handle positions look right across frames of different exposure and background level without re-anchoring by hand.
Moving the white point changes the highlights only. The background holds where the stretch factor puts it, so the three handles are independent: noise floor, background brightness, highlight headroom.
Clipped highlights
Section titled “Clipped highlights”Next to the white readout, clip is the share of sampled pixels sitting above the white point, the part of the frame being drawn as pure white. On a light frame a few hundredths of a percent is star cores and is normal. Whole percents means nebulosity is blowing out, and the white point wants to go up.
Save to rig, and Reset
Section titled “Save to rig, and Reset”Three tiers, in priority order:
- Live edit. Dragging a handle changes what you see immediately. It applies only to the frame open in the viewer and is not saved anywhere yet.
- Save to rig. Persists the current look to the frame’s rig, so every light frame on that rig opens with it from then on, until it is saved over again. The white point is included only if you moved it, so a rig you never adjusted it on keeps the headroom built in for each subtype.
- Built-in default. The per-subtype starting point every rig uses until something is saved over it.
Reset discards a live edit and returns to whatever is saved on the rig, or the built-in default if nothing has been saved.
Saving is a display preference, not a per-frame setting: it applies to the whole rig, not just the one frame you were looking at when you saved it.
What it does and does not touch
Section titled “What it does and does not touch”The stretch is a display transform. It changes what is drawn on screen and nothing else. Stored pixels, calibration, alignment, and the stack all read the same linear data whatever the stretch is set to.
A rig’s saved stretch is not confined to the open viewer. It also renders the thumbnails and filmstrips shown for that rig, so a look you save carries into the session contact sheet, Cull by metric, and every filmstrip you flip through afterward.
Calibration frames
Section titled “Calibration frames”Open a bias, dark, or flat frame and the widget is there to drag, with Reset, but there is no Save to rig control. A calibration frame is a diagnostic surface, not the rig’s presentation, so it always opens on its own built-in linear default and inspecting one can never change what the rig’s lights look like.
The transfer stays linear as you drag the white point on one of these, which makes the white handle a straight contrast control for reading dust motes, gradients, hot pixels and amp glow.