Mirroring your digital negative

An alt-process contact print is made by laying the transparency emulsion against emulsion on the sensitized paper. This physical configuration reverses the image laterally — what you see on the right on the transparency appears on the left on the final paper. If you don't account for this reversal when preparing the negative, your print comes out backwards.

The Mirror option solves this. When on, it pre-flips your image horizontally before export — the physical reversal at print time then puts it back the right way around. What can be surprising (generating a backwards image so it comes out the right way) becomes obvious once you grasp the mechanics of contact.

#How it works

Mirror — off or on. When on, the image is flipped left/right before export. Text becomes unreadable (the letters are reversed). For images with no text or marked asymmetry, the eye doesn't always notice the mirror right away — but the final print will come out correct.

The flip applies only to the useful image. The frame and the registration marks are not mirrored — they're drawn after the image is flipped, in their native orientation. This separation is deliberate: you want the frame to keep its position relative to the corners of the paper, not to follow the flip.

Orientation — portrait or landscape. Toggles the paper dimensions: if you're in A4 portrait (210 mm wide × 297 mm tall), switching to landscape gives 297 × 210. The image adapts to the new orientation by scaling or cropping depending on its native proportions.

It isn't a pixel-by-pixel rotation — it's a change of file format. If your source image is portrait and you output landscape, the app finds the best way to arrange it in the new format, with possible margins if the proportions don't match exactly.

#Why it matters

For direct-contact processes. Cyanotype, platinotype, palladium, carbon, Aquaprint, gum, Van Dyke, bromoil — all these processes use contact between transparency and sensitized paper. They all require the mirror flip on the transparency so the print comes out the right way around. It's probably the rule most often forgotten by new practitioners.

For projection or enlarger processes. Conversely, if you project your negative through an optical system (rare in current alt-process but possible), the optics already reverse the image laterally. In that case, the mirror must not be turned on — otherwise the double reversal puts the image backwards again.

For text-bearing images. On an image with text (a sign, a label, an engraved quote), the mirror is immediately visible and lets you check at a glance that the setting is the right way around before wasting paper on a backwards print.

#When to avoid it

For perfectly symmetrical images. A calibration target, a symmetrical photogram, a centered and axisymmetric still life — the mirror flip doesn't visually affect the result. You can leave the default setting with no risk.

For prints via a photographic enlarger. If your workflow uses optics that project the negative (rare), turn off the mirror — the optics will do the reversal for you.

For prints where the orientation is deliberately decided by the author. Some images are composed to be reversed (mirrored text, stylistic effects). In that case, turn off the mirror and print as is.

#Worth remembering

#The test

Load an image that contains clearly readable text (a word or a sentence). Turn on Negative mode and check the mirror: you should see the text written backwards on the preview (mirror reverse). Print the transparency and expose in contact on sensitized paper. Once developed, the text on the final print should be readable normally. If the text is still backwards on the print, either the mirror wasn't applied, or you printed with the transparency emulsion facing up instead of down.