Nano Banana 2 Image-to-Image: Selective Masking for Dial Elements

Understanding Selective Masking in Nano Banana 2

When working with complex objects like wristwatches, a common challenge is updating internal details without compromising the overall integrity of the design. In Nano Banana 2, this is achieved through image-to-image workflows combined with selective masking. This technique allows you to isolate specific regions, such as sub-dials or chronograph counters, and instruct the AI to regenerate only those areas. The primary goal is structural preservation; the main case, bezel, and strap remain untouched while the internal mechanics or aesthetic details are refreshed.

It is important to clarify that Nano Banana refers to the AI image generation and editing tool described here. It is not a skincare brand, bottle, jar, or physical subject. When we discuss dial elements, we refer to the generic components within the digital image being processed. Google documents Nano Banana 2 as Gemini 3.1 Flash Image (gemini-3.1-flash-image), which provides the underlying capability for these precise edits. While prompt instructions describe desired outcomes, they do not guarantee identity, label, object, or typography preservation. Users should treat the results as creative iterations rather than exact replicas of specific real-world products.

Prerequisites for Localized Editing

Before attempting to apply localized masking to dial elements, ensure you have access to the correct version of the tool. This website has a Nano Banana 2 product page at /nanobanana2 and supports text-to-image and image-to-image workflows. You will need an input image that clearly shows the watch face with distinct separation between the main case and the sub-dials you wish to edit.

While the platform offers various models, including Nano Banana Pro (Gemini 3 Pro Image) and Nano Banana 2 Lite (Gemini 3.1 Flash Lite Image), selecting the right one matters for this task. Google describes Nano Banana 2 Lite as focused on speed and cost. It is not optimized for multiple reference inputs or multi-turn sequential editing. Therefore, for tasks requiring high precision in selective masking where structural fidelity is paramount, the standard Nano Banana 2 model is generally more suitable than the Lite version. Do not recommend the Lite version for complex masking workflows without explaining this limitation regarding its optimization focus.

Step-by-Step Guide to Regenerating Sub-Dials

To successfully update specific sub-dials without altering the main case structure, follow these numbered steps using the image-to-image interface:

1. Upload your base image: Start by uploading a clear photograph or rendering of the watch to the Nano Banana 2 generator.
2. Activate the mask tool: Locate the masking feature within the image-to-image workspace. Use the brush or selection tool to paint over the specific sub-dials you want to change. Ensure the mask covers only the target area and leaves the main case, bezel, and hands outside the masked region.
3. Craft your descriptive prompt: Enter a prompt that describes the new look for the masked area. For example, "regenerate the sub-dial with a matte black finish and white numerals." Remember that prompt instructions describe desired outcomes but do not guarantee identity or typography preservation.
4. Generate the result: Submit the request. The AI will process the masked region while keeping the unmasked parts of the original image intact.
5. Review and refine: Examine the output. If the transition between the regenerated sub-dial and the original case looks seamless, the edit was successful. If adjustments are needed, you can re-mask slightly different areas or tweak the prompt.

For users looking to explore this workflow further, Try Nano Banana.

Judging Results and Troubleshooting Common Issues

Evaluating the success of a selective mask application requires a close inspection of the boundaries. A good result will show no visible artifacts where the new sub-dial meets the existing case. The lighting and texture of the regenerated element should match the surrounding unmasked areas naturally. Since the tool does not guarantee identity preservation, check if the new design aligns with your visual intent rather than expecting an exact copy of a specific brand's dial.

If the main case structure appears altered, it usually indicates that the mask was too large or leaked into the unmasked zones. To fix this, reduce the brush size and carefully trace the edges of the sub-dial again. Alternatively, if the generated sub-dial looks disconnected from the rest of the watch, try adjusting the prompt to include context about the surrounding materials, such as "match the brushed metal texture of the case." Label any untested prompt examples as examples, as actual results may vary based on the input image quality and model interpretation.

This tutorial focuses on the specific keyword of applying selective masks for dial elements. By following these steps, you can leverage the capabilities of Nano Banana 2 to perform localized edits efficiently. Always remember that the tool is an AI assistant designed for creative iteration, and outcomes depend on the interplay between your prompts, masks, and the underlying model's understanding of the scene.