Nano Banana 2 vs Imagen 4 — when to pick which (and why I ship both)

A question I get often: "If GeminiOmni already has Nano Banana 2, why do you also expose Imagen 4? Aren't they the same thing?"

They are absolutely not the same thing, and the fact that this is a confusing question is partly Google's fault. They sit in the same product family, share a backbone, and ship around the same time. But they do very different jobs, and choosing the wrong one for a given task will cost you both money and quality.

This is the cheat sheet I wish I'd had when I started building /tools/nano-banana-edit.

The one-line rule

Nano Banana 2 edits images. Imagen 4 generates them.

Yes, both can produce a JPEG when you're done. But they were built for different verbs. If you have an image already and want to change something specific about it, use Nano Banana 2. If you have a blank canvas and want to create something from scratch, use Imagen 4.

The longer you ignore that distinction, the more money you'll burn. Let me show you why.

What each one actually is

Nano Banana 2 is the public marketing name for Gemini 3.1 Flash Image Preview. It's the successor to the original Nano Banana (Gemini 2.5 Flash Image), which launched in August 2025 and did 200 million image edits in its first month — by far the fastest-adopted image model in Google's history. The defining feature is chat-based, in-context editing: you upload an image, describe what to change conversationally, and the model preserves everything you didn't mention.

Version 2 (released early 2026) upgrades the original on three axes: native 2K output instead of 1K, 16-bit color depth instead of 8-bit, and a substantial improvement in legible text rendering inside images. That last one matters more than it sounds — diffusion models have historically been hilariously bad at writing readable words in images, and Nano Banana 2 mostly fixes that.

Imagen 4 is Google's flagship text-to-image generation model, currently shipping in three tiers (Fast at $0.02/image, Standard at $0.04/image, Ultra at $0.06/image). It is purely generative: you give it a text prompt and it produces a new image from scratch. There is no "edit" mode, no in-context iteration, no chat. It does one thing — turn text into a photo — and does it extremely well.

The pricing actually tells you when to use which

Here's the part nobody writes down in plain English.

Nano Banana 2 is priced per edit, with cost ranging from $0.045 to $0.151 depending on resolution and complexity. That's 2–4× the cost of an Imagen 4 Standard image. The trade-off: Nano Banana lets you iterate on the same subject through five, ten, twenty edits and keep the character/scene consistent throughout. If you're doing a single one-shot generation, that consistency is dead weight you're paying for.

Imagen 4 Fast at $0.02/image is the cheapest generative image API I know of from a flagship lab. If you need 100 product mockups, 100 hero images, 100 stock-photo replacements — and each one is independent — Imagen 4 Fast is the right answer and Nano Banana would be malpractice.

The decision rule that falls out of this:

Three real prompts that show the difference

Sometimes a side-by-side helps more than a table. Here are three prompts where the right tool is unambiguous.

Prompt 1: "A coffee mug on a wooden table with morning light through a window."

This is generative. There's no source image. There's nothing to preserve. Send it to Imagen 4 Fast. You'll get a clean photoreal mug for two cents and you'll be done in three seconds. Sending this to Nano Banana 2 is paying triple for nothing.

Prompt 2: "Take this photo of my coffee mug and add a small succulent next to it, then change the lighting to golden hour."

This is editing. There IS a source image. You need to preserve the mug's identity, the table's grain, the window position. You want to add a specific element and modify the lighting without redrawing the whole scene. This is Nano Banana 2's job. Imagen 4 cannot do it at all — it has no source-image input mode.

Prompt 3: "Generate 10 variations of this product packaging mockup, each with a different background color, keeping the label and bottle shape pixel-identical."

This is the trickiest one. Naively, ten Imagen 4 Standard calls cost $0.40 total, while ten Nano Banana 2K edits cost $0.45–$1.51. Cheaper to use Imagen, right?

Wrong, because Imagen will give you ten DIFFERENT bottle shapes. There's no input-image conditioning on Imagen 4 — every call starts from scratch. Nano Banana 2 is the only option here. The "consistency tax" is the entire reason you're paying more per call.

What I built on top

The default route in /tools/nano-banana-edit is Nano Banana 2, because the page is explicitly framed as an image editor. If you arrive on /tools/nano-banana-edit you're not asking "create an image of a cat from nothing." You have an image and want to change it.

/ai-image-generator routes to Imagen 4 Fast by default, with a paid toggle for Imagen 4 Standard. That page is for the "blank canvas" use case.

I considered merging the two pages into a single "smart" image tool that auto-routes based on whether you uploaded a source image. I decided against it. The mental model is different — editing and generating are different verbs — and forcing them into one UI obscures the choice instead of clarifying it.

The pricing follows from the cost structure:

• Free tier: 10 Nano Banana edits/month or 20 Imagen 4 Fast generations
• Pro $19/mo: unlimited Nano Banana 2K + 100 × 4K, unlimited Imagen 4 Standard
• Team $79/mo: unlimited everything at every resolution + 3 seats

I named the per-call model on every output, like with the video tools. The image carries a small caption showing whether it came from Nano Banana 2 or Imagen 4 Standard. People deserve to know which model spent their cents.

The one place the line blurs

There's exactly one workflow where the line genuinely blurs, and it's the place I expect Google to consolidate next.

If you generate an image with Imagen 4 and then immediately want to iterate on it ("make it warmer," "remove the second cup") — you can. You hand the Imagen 4 output to Nano Banana 2 and start editing. Two model calls. Costs $0.04 + $0.05 = $0.09. Works fine.

But the round-trip is friction. The two models don't share state, the seed isn't preserved, and you're paying twice. The obvious product fix is a unified "generate + edit" model that uses Imagen-class quality on the first call and Nano Banana–style chat editing thereafter, with the seed and reference image tracked internally.

Whether Google ships that at I/O 2026 next week, or whether it's the Gemini Omni model I wrote about doing it natively, I don't know. If it does ship, the bottom row of the table above gets a third column, and I'll write that up the day it lands.

Read next

• Nano Banana 2 — chat-based image editor
• AI image generator — Imagen 4 default
• GeminiOmni pricing

— Lena