ChatGPT Images 1.5 vs Gemini Nano Banana Pro: OpenAI announced the global rollout of ChatGPT Images 1.5 on 17 December, promising faster, more precise and flexible image generation directly within ChatGPT. The update immediately caught my attention, especially since Google’s Gemini Nano Banana Pro has already made waves with its August release.
So, I decided to run a simple experiment: I uploaded my own selfie and used two identical prompts across both tools to see how they would transform me.
Comparing AI performance with common prompts
To test the upgrades, I used two prompts across both ChatGPT Images 1.5 and Gemini Nano Banana Pro.
Prompt 1 (K-pop Idol Transformation)
Using the provided image of the subject as a reference, transform them into a K-pop idol–style version of themselves, fully preserving their natural facial features, skin tone, ethnicity, and identity. Style the subject with a polished, high-fashion idol aesthetic inspired by contemporary K-pop concept photoshoots, featuring editorial studio lighting with a soft glow and clean highlights, a flawless yet natural dewy skin finish, and subtle enhancements to the eyes, lips, and hair for a camera-ready look. The subject poses confidently with expressive yet controlled body language, styled in fashion-forward outfits influenced by modern K-pop trends, such as elevated streetwear, Y2K accents, chic tailoring, glam punk, or soft, ethereal looks, all adapted to complement their original clothing style. The atmosphere resembles a professional idol photoshoot, incorporating bold, coloured backdrops or moody, dramatic environments, studio or concert-style lighting, cinematic shadows, and refined colour grading, with optional tasteful details like layered jewellery, belts, or statement accessories kept cohesive and restrained. The final image should feel like an authentic K-pop concept photo—crisp, stylish, and aspirational—projecting polished charisma and star presence while clearly remaining the same person.
Both AI tools performed exceptionally well. Gemini Nano Banana Pro worked faster, finishing in about 35-40 seconds, while ChatGPT Images 1.5 took longer (around 60 seconds), but the outfits and backgrounds were more vibrant.
Prompt 2 (Chibi Character Transformation)
Prompt: Transform the subjects or image into an adorable Chibi-style character with a tiny body and an oversized head. If the image contains a person or multiple people, give them large, sparkling eyes, soft rounded facial features, and a cheerful expression, while preserving their recognisable traits such as key facial features, hairstyle, accessories, or distinctive clothing. If the image contains an object, animal, or scene, reinterpret its most recognisable features using the same Chibi proportions and simplified, cute styling. Keep the overall look short and cute, with smooth pastel shading and simplified details. Make the final image bright, expressive, and irresistibly charming, like a collectible Chibi mascot.
For Chibi transformations, both ChatGPT and Gemini produced high-quality results, though Gemini Nana Banana captured background elements slightly better and rendered more realistic Chibi facial and clothing features. ChatGPT Images 1.5 was again slower (about 60 seconds).
What I learned
This experiment showed me that ChatGPT Images 1.5 excels at vibrant styling and detailed transformations, while Google’s Gemini Nano Banana Pro wins on speed and background accuracy.
The standout feature of ChatGPT Images 1.5, though, is editing precision. I could change only selected parts of my selfie, like adjusting clothing or adding accessories, without affecting the rest of the image. It even allowed to blend multiple images into one cohesive scene.
Instruction-following was another big plus. When I gave detailed editing instructions, ChatGPT Images 1.5 changed only what I asked for, resulting in:
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