greycard

User guide

Merging frames

Several frames of one scene can be merged into one: a bracket into an HDR, a turn of the camera into a panorama, or a run of focus distances into a focus stack. Each merge is a DNG you edit like any other frame.

Merge to HDR

A bracket, the same picture at several exposures, on a tripod or by hand, can be merged into one frame that holds the shadows of the brightest frame and the highlights of the darkest.

  • Select the bracket's frames, two or more, of one camera and one size, and choose Merge to HDR on the frame menu. The status line says each frame as it is read; a 45-megapixel frame takes a few seconds.
  • The merge is a DNG beside the first frame, named after it: IMG_0001-HDR.dng, or IMG_0001-HDR-1.dng when that name is taken. When the frames share one folder and you are not in a collection, it goes on top of a stack with them.
  • The file is a compact float DNG: about 170 MB for three 45-megapixel frames.
  • It opens looking as the middle exposure did, with that frame's edit (its exposure left at zero), and the highlights the middle frame lost are there to bring down with Highlights or the exposure. Highlights at −100 brings the brightest of them just under white.
  • A frame that moved between shots, by a hand's shift, turn, or lean-in, is put back in place, and the log says how far. When one did, whatever moved in the scene itself (a person, a branch, a wave) is taken from the middle frame alone rather than doubled. A near scene shot by hand still shows parallax no merge removes.
  • Asking for a second merge while one runs starts it when the first is done, and the status line says so.
  • The file is never seen half-written: it is written under a hidden name and renamed when done. If a merge is cut short, its hidden part file is removed the next time you merge to that name.

From the command line: greycard merge hdr IMG_0001.CR3 IMG_0002.CR3 IMG_0003.CR3, with --reference to pick the frame the others are put on (counting from 0), --out to name the file, and --on-exists for when that name is taken.

Merge to Panorama

Frames shot turning the camera, each overlapping the next, can be stitched into one wide frame.

  • Select the frames, two or more, of one camera, one size, and one focal length, in the order you shot them, and choose Merge to Panorama on the frame menu. The status line says each frame as it is read, then as it is blended in.
  • The frames' lens is corrected first, from its profile, as the develop would correct it, and the develop does not correct the panorama again. With no profile for the lens, or the Lens section off, the frames are stitched uncorrected, and the log says so.
  • Up to about 90 degrees across, the frames are laid flat; wider, on a cylinder, which holds up to 120 degrees across the turn. A camera whose focal length or sensor size is not known is always laid flat, and the log says so.
  • The frames' brightness and color are matched where they overlap, and each seam is led around what differs between them, so a person who moved, or something close to the lens, comes from one frame rather than twice. Turning the camera about the lens itself, on a tripod's panorama head, leaves the least to hide.
  • The result is cropped to the largest rectangle the frames cover, and is held to 100 megapixels for now.
  • The merge is a float DNG beside the first frame, named after it: IMG_0001-pano.dng, numbered when the name is taken, and on top of a stack with its frames, as a merge to HDR is. It is seen from the frame in the middle of the turn, whatever order you shot in, and opens with that frame's look: its edit less its exposure, its lens corrections, its crop and straightening, its retouching, and its masks, which were placed on one frame.
  • When that edit uses the learned denoiser, each frame is denoised as it is read.

From the command line: greycard merge pano IMG_0001.CR3 IMG_0002.CR3 IMG_0003.CR3, with --reference to pick the frame the others are turned onto (counting from 0), --out to name the file, and --on-exists for when that name is taken. A second merge to a file that one is still writing is refused.

Merge to Focus stack

Frames of one subject shot at several focus distances can be merged into one frame that is sharp everywhere.

  • Select the frames, two or more, of one camera and one size, in focus order, and choose Merge to Focus stack on the frame menu. The status line says each frame as it is read. Every frame is held in memory at once, about a gigabyte a frame at 24 megapixels, and a stack the computer's memory will not hold is refused: stack fewer frames at a time.
  • The frames are put onto the middle one, scale included, since a lens breathes as it focuses. A frame that cannot be lined up is left out, and the log says which and why.
  • The merge is a DNG beside the first frame, named after it: IMG_0001 stack.dng, numbered when the name is taken, and on top of a stack with its frames, as a merge to HDR is. It opens with the middle frame's edit, its exposure kept, less the learned denoiser.
  • A focus stack keeps no recipe, so it is not made again from the Noise section: merge its frames again instead.

From the command line: greycard stack IMG_0001.CR3 IMG_0002.CR3 IMG_0003.CR3, with --reference to pick the frame the others are put on (middle, sharpest, or a number counting from 0), --selectivity and --max-residual to tune the merge, -o to name the file (a .tif writes a 16-bit linear TIFF instead), --uncompressed, and --on-exists for when that name is taken.

Making a merge again

A merged file keeps its recipe: its frames' names with a check of each, the merge's options, and where every frame was placed. While the frames are beside it, unchanged, it can be made again from them.

  • In the window, open the merged file: in the Noise section the learned denoiser's tiers give way to a row of their own over Denoise the frames and merge again. The tiers start at the one the merge ran, or off when none ran. Pick one and press the button; the status line follows the merge as it runs, and the picture reloads when it is done. The row is not there when a frame is missing or changed, when the frames are not ones the learned denoiser takes (X-Trans), or when sidecars are off, and it waits while another merge runs.
  • greycard merge again IMG_0001-pano.dng --denoise balanced merges the frames again with the learned denoiser on each (fast, balanced, best, or none). The frames land where they did, to the pixel, so the file's edit, crop, and masks still fit; only the noise changes. Nothing is matched or fitted again, so it is quicker than the first merge.
  • The file is replaced under its own name, and its edit kept; --out writes it elsewhere instead.
  • A frame missing from beside the file, renamed, or changed since is named, and nothing is written. A file merged before recipes were kept is refused: merge its frames again.