The cut-out is a green screen you never see

There is a moment after a photo set comes back where the work stops being generative and starts being ordinary. The pictures exist. Now one of them has to become the square main image, and another has to sit on a coloured banner with nothing behind it, and the one you want to print needs to be bigger than it is. Three buttons offer to do exactly those three things, in one click each.

It is worth knowing what the click does, because the mental model almost everyone brings to it is wrong in a way that costs credits and occasionally costs a listing.

A finish is a re-render, not a transform

Reach for the background remover in a photo editor and it works on your pixels. It finds an edge, cuts along it, and every pixel that survives is the pixel you had. The product cannot change, because nothing is being drawn.

That is not what happens here. Each of the three finishes sends your still back to the image model with an instruction to produce the product again — identical geometry, identical proportions, identical colours and materials and surface texture, identical label placement, every character of text verbatim, same camera angle and framing — and to change only the one thing being asked for. The white-background version is a new rendering of your product standing on seamless white. The 4K version is a new rendering of the same frame at a higher resolution. Neither is your file with an operation applied to it.

Most of the time the distinction is invisible, which is why it is worth stating. The instruction is strict and the model is being handed the answer, so a packshot usually comes back indistinguishable from the still it was made from except in the respect you asked about. But the failure mode is not an editor's failure mode. An editor that goes wrong leaves a ragged edge. A generation that goes wrong can hand you a product whose engraving reads slightly differently — and if you are not looking for that, the white background you were checking for will look perfect.

So the thing to check on a finish is not the finish. It is the part you did not ask to change: the text, the logo lockup, the number on the dial, the spelling on the cap. The same inspection a first render deserves, for the same reason, because it is the same kind of event.

The cut-out takes a detour through green

The transparent PNG is the one finish that is not a single step, and the reason is a limitation worth understanding rather than working around.

An image model has no alpha channel. It produces colour for every pixel in the frame; there is no way to ask it for an absence. So transparency cannot be generated — it has to be manufactured afterwards, which means the picture first has to be rendered onto something that can be identified and removed.

That something is chroma green: a single flat value, #00FF00, filling every pixel the product does not cover, with no shadow, no gradient and no reflection permitted. The model renders that. Then ffmpeg — deterministic software, not a generation — keys the green to transparency and runs a despill pass so the edges do not carry a green fringe where the background bled onto them. What you download is the second half of that pipeline's output.

The green is not arbitrary. It was chosen because pure chroma green is essentially absent from product photography: almost nothing a seller lists is that colour, so almost nothing a seller lists is at risk of being keyed away along with the background. The tolerance is set deliberately loose, because the model's idea of flat green is slightly uneven, and deliberately tight, because the looser it gets the more of a genuinely green product it eats.

Which gives you the one case this finish cannot serve. A lime-green bottle keys badly. A product that is close to chroma green, or glossy enough to throw green from the background onto its own surface, will come back with bites taken out of it or with a halo where the despill could not decide. That is a known limit, the app says so at the button, and the answer is not to fight it: use the white background instead and composite against white, or shoot the product against a background that contrasts with it and keep the backdrop.

Two finishes are two photographs

This is where the re-render model starts to matter economically. Suppose you want a 4K white-background packshot. There is no single button for it, and the reason is now obvious: it is two generations. The still goes to the model to be placed on white; that result goes back to the model to be rendered larger. Two re-renders, stacked, each one a fresh opportunity for the model to be very slightly less careful about the engraving.

It also costs what two things cost. A white background is ten credits. A cut-out is ten credits. The 4K upscale is twenty, not because upscaling is harder to ask for but because it is priced as what it produces — a 4K still, which is what a 4K still costs anywhere else in the tool. So the pair is thirty credits and two inspections, and both of those are worth knowing before you start rather than after.

The practical consequence is an ordering question. If the final asset has to be both large and on white, do the white background first and the upscale second: the upscale is the more expensive step and the one you least want to repeat, so it should be the step that runs on an image you have already approved. Running it the other way round means that if the packshot comes back wrong you have thrown away the twenty-credit operation along with the ten-credit one.

And if the final asset only needs to be one of those things, do not stack. A marketplace main image is almost never served better by being four times larger than the specification asks for, and every finish you skip is a generation that cannot go wrong.

What the three are actually for

Taken together they are not an editing suite and they are not trying to be. They are three finishes for three destinations, and each one answers a question the original still could not.

• White background — the main image. The picture that has to look like every other main image on the page it lands on, which is a constraint about conformity rather than beauty. Check your own store's image specification for the size and margin it expects; the finish gives you the seamless white, not the crop rule.
• Cut out — the composite. The transparent PNG exists so the product can sit on something you control: a coloured panel, a seasonal banner, an ad layout, a comparison grid. It is the only one of the three whose output is not a finished picture but an ingredient.
• Upscale to 4K — the large format. Print, a hero banner, a surface where someone will see the texture. Worth twenty credits exactly when something is going to be looked at closely, and worth nothing at all on an image that will be displayed at four hundred pixels wide.

None of the three is a way to fix a photograph you do not like. That is the other half of the re-render model: because each finish is handed the product and told to keep it, a finish cannot improve the thing you were unhappy about. A poorly lit still, finished onto white, is a poorly lit still on white. The place to change what the picture is of is further back, in the shoot that made it.