Guides

1K, 2K, 4K: when 4K is worth 24 credits

One prompt run at all three sizes on Nano Banana Pro. What the extra pixels resolve, what a 4K image prints at in centimetres, and why the three sizes are three different pictures rather than one.

September 20, 20266 min readAIKIZI

Part 3 of 11 · ← previous · all parts · next → Style references, 3 and 10

4K costs 24 credits against 1K's 8 on Nano Banana Pro. It is worth it when the picture will be printed, or cropped into, or looked at closely — and it is worth nothing at all if you are still deciding the composition. We ran one prompt at all three sizes and found something we did not expect: the three sizes are not one picture. They are three different pictures.

The finding first, because it changes how you spend

We assumed, as most people do, that resolution is a quality dial on a fixed image: same lamp, same garland, same light, more pixels. It is not. Each size is a separate generation. Below are the three runs of one prompt, in order, with nothing changed between them but the size setting.

1K version: the lamp centred slightly right, garland coiled tight around the base, a shaft of light and dust motes crossing from upper left, background wall simplified — Nano Banana Pro, 1K, 8 credits. Tight frame, one shaft of light, dust in the beam.

2K version: the garland now drapes over the edge of the step in a long strand, moss on the stonework, clear water beads on the brass stem, a taller flame — Nano Banana Pro, 2K, 16 credits. The garland now drapes over the step edge, moss has appeared, the water beads the prompt asked for are finally on the brass.

4K version: a wider deeper frame, the granite's speckled grain fully resolved, individual marigold petals separated, patina and pitting on the brass, the flame with a visible hot core — Nano Banana Pro, 4K, 24 credits. Wider, deeper, and the granite grain, the petal edges and the brass pitting all resolve.

Look at the garland across the three. It is coiled, then draped, then ringed. The lamp moves. The background rebuilds itself each time. You are not buying the same picture at a better size; you are buying another roll of the same idea.

What that means for how you work

The practical rule falls straight out of it, and it is the opposite of what people usually do:

Draft at 1K, or at 2 credits on Nano Banana 2 Lite. You are deciding the subject, the framing and the light; you are not judging texture yet.
Finish at 2K once the words are right. 16 credits, and it is the size most screens, posts and client previews will ever need.
Go to 4K only when the output is print, or a crop, or something a person will put their face close to.
If you already have a composition you love at a smaller size, do not regenerate at 4K hoping to keep it. Upscale it for 15 credits instead — that keeps the picture you have.

The sizes, in money and in centimetres

Print is the case where 4K stops being a luxury. At 300 dpi — the normal figure for a photographic print — the arithmetic is fixed and short.

Size	Long edge, roughly	At 300 dpi	Credits · Pro	Credits · NB2
1K	1024 px	8.7 cm · postcard, and small for one	8	4
2K	2048 px	17.3 cm · a book page	16	8
4K	4096 px	34.7 cm · A3-ish, framed	24	12

On a screen the picture is over-supplied long before that. A full-width image on a normal laptop is about 1400 pixels across; a phone is less. 2K already has more pixels than either will show. Which is why the honest answer to "should I always work at 4K" is no, and the answer to "should I print at 1K" is also no.

Where the extra pixels actually show

Three things resolve at 4K that do not at 1K, and all three are material rather than compositional: the speckle in the granite reads as individual grains instead of noise; the marigolds separate into petals instead of orange masses; the brass shows patina and pitting rather than a smooth gradient. If your picture's subject is a surface — fabric, skin, metal, stone, food — that is where your 24 credits go. If your subject is a shape against a sky, they go nowhere.

The cost of finding out the expensive way

Generating one idea at all three sizes cost 48 credits, which on the Pro plan is about a ninth of the month for one lamp. Doing it as drafts first — three Lite passes at 2, then one 2K at 16 — would have cost 22 and answered the same question. We spent the 48 so this page could show you the difference; you do not have to.

FAQ

Is 4K worth 24 credits?

For print, for crops and for pictures whose subject is a surface — stone, metal, fabric, skin — yes. For screens, no: 2K already carries more pixels than a laptop or a phone displays. 4K is three times the price of 1K and about sixteen times the pixels.

Does generating at 4K give me the same image as 1K, only bigger?

No. Each size is a separate generation, so the composition changes with it. In our three runs of one prompt the garland was coiled at 1K, draped at 2K and ringed at 4K, and the background rebuilt itself each time.

How big can I print a 4K AI image?

About 34 cm on the long edge at 300 dpi, so roughly A3 framed. 2K gives about 17 cm, a book page. 1K gives under 9 cm, which is small even for a postcard.

What size should I use for Instagram or a website?

2K is already more than either shows. A full-width image on a laptop is about 1400 pixels across and a phone is less, so 16 credits on Nano Banana Pro or 8 on Nano Banana 2 is the sensible finishing size for screens.

How do I keep a composition I like and still get more pixels?

Upscale it for 15 credits rather than regenerating at 4K for 24. The upscale works on the picture you already have, so the composition survives; a new 4K generation makes a different picture.

The quickest way to feel this is to run one prompt twice at two sizes yourself in the Studio. If you have a picture you already like, read part 8 before you spend 24 credits on a second try.