光と影 – AI画像生成でモノクロームフィルムの触感を再現する

はじめに

子供の頃から写真撮影を趣味として生きてきた。1960年代から70年代はモノクロームフィルムが一般的だった。カラーフィルムは現像も焼き付けも非常に高価だった。そのような現実的、経済的な負担を考え、結局現在に至るまで、自分を取り巻く世界をモノクローム階調で捉えることに専念してきたように思います。

2024年夏、歩行に支障を来たし、ストリート撮影が困難に。以来、AI画像生成がストリート撮影に置き換わり、現在まで約20,000枚以上を生成してきました。
プロンプトにも慣れると「なんでも生成できてしまう、しかしそこには何もない」、ということに気づいた。写真芸術の精神性から程遠い泥沼に足を取られ、ノイジーな生成結果に一喜一憂している自分自身に危機感を感じるようになった。
AI画像生成は、伝統的な写真撮影では難しかった表現の場を提供してくれていることは間違いない。モノクローム写真の経験が、AI生成画像のプロンプト作成に直接活かせることもわかってきた。今、取り組むべきことは「AI画像生成を使って何を表現すべきか？」ということです。シャッターを切るという行為を単にAIに置き換えるのではなく、これまでの経験を強化させるということではないだろうか、そのように考えるようになってきました。

Two silhouetted figures carrying umbrellas and bags, walking along a cobbled street towards the viewer, next to dark buildings, in a city street.
SHOT ON A LEICA M11 + SUMMILUX 50mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, 
Style: Black and White Photography, Street Photography
Lighting: Dramatic Lighting, High Contrast
Composition: Eye-level shot, Diagonal lines
Details: Strong shadows, sunlight patches on cobblestones, urban atmosphere, dark building facades
Quality: High Detail, Masterpiece

Black and white photograph, dramatic high contrast lighting, chiaroscuro, street photography style, two figures with umbrellas walking on a cobbled street at golden hour, long shadows, detailed cobblestones, classical architecture with arched doorways and intricate carvings, moody atmosphere, sense of mystery

モノクローム表現の専門知識は、AI画像生成で大きな強みになります。例えば「夕日の入射角45度、大気透視効果を適用」というように光の物理的記述を加えると有効な効果が得られることがあります。このように光と影、構成の技術を活かし、詳細なプロンプトを作成することで、AIがビジョンに合った画像を生成するよう工夫します。
さらに「プロンプト設計の黄金律」ということがよく言われますが、難しいことではなく、私は次のように簡略化しています。

(被写体の詳細), (背景設定), (照明条件), (追加効果) // 撮影機材情報

次の課題としてフィルムと印画紙の特性を再現しようと考えています。（今はデータを整理中です）

AIモノクローム表現、最近の実験結果です

A silhouette of a person walking toward the viewer along a cobblestone path, holding an umbrella and a bag. A Parisian alleyway covered by an archway in the rain, surrounded by dark buildings shrouded in fog. Long shadows stretching across the rain-soaked cobblestones.
Camera equipment: LEICA M11 + SUMMILUX 50mm F/1.4, extremely detailed description, sharpness, detail, professional lighting, noir, cinematic, deep shadows,  
Style: Black and white photography, street photography  
Lighting: Dramatic lighting, high contrast  
Composition: Shot from eye level, diagonal lines
Details: Strong shadows, sunspots on the cobblestones, urban atmosphere, dark building facades  
Quality: High detail, masterpiece  
Black-and-white photography, dramatic high-contrast lighting, chiaroscuro, street photography style, a person holding an umbrella walking along a cobblestone path at golden hour, long shadows, detailed cobblestones, classical architecture with arched entrances and intricate carvings, moody atmosphere, mystical feel

日本語訳（英文を推奨します-ご参考までに）
傘とバッグを手に持ち、石畳の道を視聴者の方へ歩いてくるシルエットの人物。雨の降るアーチに覆われたパリの路地、霧が立ち込める暗い建物に囲まれた都市の街並み。雨に濡れた石畳に延びる長い影。
撮影機材：LEICA M11 + SUMMILUX 50mm F/1.4、極めて詳細な描写、シャープネス、ディテール、プロフェッショナルな照明、ノワール、シネマティック、深い影、  
スタイル：モノクロ写真、ストリート写真  
照明：ドラマティックな光線、高コントラスト  
構図：目線の高さからの撮影、対角線
詳細：強い影、石畳に差し込む日光の斑点、都市の雰囲気、暗い建物の外壁  
品質：高詳細、傑作  
モノクロ写真、ドラマティックな高コントラスト照明、 Chiaroscuro、ストリートフォトグラフィースタイル、傘を差した人物が黄金の時間に石畳の道を歩く、長い影、詳細な石畳、アーチ型の入り口と複雑な彫刻を備えた古典的な建築物、 moodyな雰囲気、神秘的な感覚

A middle-aged woman carrying an umbrella walks through the dimly lit, damp cobblestone streets of old Paris at night, illuminated by gas lamps.  
Style: Black-and-white photograph  
Lighting: Streetlight illumination, moody lighting  
Composition: Medium-range shot, rule of thirds  
Details: Cobblestone patterns, damp road, misty atmosphere, Parisian downtown architecture, faintly lit windows of buildings, moody, mysterious  
Quality: High detail, masterpiece, cinematic.

Adjust the overall setting with misty rain and light fog to softly diffuse the light.

Car headlights in the background.

傘を差した中年の女性が、古いパリの路地裏、ガス灯が照らす夜の薄暗い湿った石畳の道を夜に歩いている。  
スタイル：モノクロ写真  
照明：街灯の光、ムードのある照明  
構図：中距離ショット、三分割法  
詳細：石畳の模様、湿った道、霧の雰囲気、パリ下町の建築物、建物の窓の薄明るい照明、ムードのある、神秘的な  
品質：高詳細、傑作、シネマティック。

霧雨と軽い霧で全体の設定を調整し、光を柔らかく拡散させる。

背景には乗用車のヘッドライト。

水たまりに映った風景と自転車の車輪を捉えるというアイデアは珍しいものではありません。しかし複雑な要素をAI画像生成で正確に表現するのは結構難しく、どのように言語化（プロンプト化）すべきか試行錯誤をする必要がありました。
掲載画像は無料で試せるGoogle Imagen3 (ImageFX)、Promptは「Universal 」で出力。「恐るべしGoogle!」を実感。
ご参考までにFlux、Midjouney、Stable Diffusion用のプロンプトも記載しておきます。

Flux Prompt:
A close-up view through the spokes of a bicycle wheel, revealing a street scene with grand Parisian buildings reflected in a puddle, Paris. 
Style: Black and white photography Lighting: Overcast natural light 
Composition: Low angle view capturing reflection and composition through spokes, symmetrical reflection 
Details: Wet street after rain, bare trees, detailed architecture, distorted view through wheel, water ripples. 
Quality: High detail, Photorealistic, Masterpiece

Midjourney Prompt:
A close-up, low-angle shot showcasing the top half of a bicycle wheel in the foreground, with the background featuring a view of intricate Parisian architecture reflected in a large puddle on the street below, all rendered in black and white.
Black and White Photography
Natural Light
Wide Shot with reflected view
High Contrast, Wet Street, Urban Reflection, Parisian Architecture, Detailed Building Facade, Bicycle Wheel Spokes
--ar 4:5
--v 6.0

Stable Diffusion Prompt:
Black and white photograph, urban street scene, bike bokeh foreground, Parisian architecture reflection in puddle (strong focus, wet pavement reflection), dramatic B&W processing, blurry foreground bike wheels, clear reflection, detailed buildings, dark tones, high contrast, wet street, bare trees; --ar 2:3 --stylize 800

Negative prompt: color, blurry background, distorted reflection, low detail, flat lighting, oversaturated

Universal Prompt :
black and white reflection photograph capturing the upper portion of a bicycle wheel with sun rays emanating from the center, framed by a detailed Paris apartment building on a stormy day with a puddle reflecting the building and the other half of the bike wheel the bokeh effect gives the photo a dreamy feel, The composition is striking, with the bike wheel dominating the foreground and acting as a frame for the cityscape behind. the depth of field is very shallow creating a beautiful bokeh effect which adds to the dreamy and romantic ambiance of the image. the lighting is dramatic, with harsh shadows and highlights that create a sense of mystery and intrigue. The overall mood of the photograph is melancholic and evocative of a rainy day in Paris. The image is shot in black and white, which gives it a timeless and classic feel, reminiscent of a vintage postcard from Parisian streets. The image is a powerful example of how to use reflections and composition to create a visually striking and emotionally resonating photograph. it's a beautiful piece of work that captures the essencia of Paris on a rainy day, inviting the viewer to reflect on the beauty and poetry of the commonplace, by a French photographer --ar 2:3 --s 700 --style raw

GPS_48.8566 N, 2.3522 E, a man opening the door of a vintage Citroën and getting in on a rainy Parisian backstreet. The man is holding a paper bag filled with vegetables. A stray cat, wet from the rain, looks up at the man from the ground. The man looks back at the stray cat. Minimalist street photography. emphasizing high contrast, light-to-shadow ratio (2:8), intricate details, resolution, 4K, 8K, photos SHOT ON A LEICA M11 + SUMMILUX 50mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, --ar 16:9 --v 5 --style 4b" monochrome. chiaroscuro minimal highly detailed realistic.

People walking reflected in a storefront window with "or" and "Miss Dior The New Parfum" visible, showcasing urban life and advertisement.
Style: Black and White Photography
Lighting: Strong sunlight casting shadows
Composition: Medium shot, reflection highlighting layers of reality
Details: Textured building facade, details of advertising imagery, movement of people creating blurred reflections
Quality: High detail, (((Sharp focus on reflections))), Street photography aesthetic, hyper-realistic, fine textures, rich details, shot on Canon EOS R5, 35mm f/1.8.

a man opening the door of a vintage Citroën and getting in on a after the rainy,  Parisian backstreet. The man is holding a paper bag filled with vegetables. A stray cat, wet from the rain, looks up at the man from the ground. The man looks back at the stray cat. Minimalist street photography. emphasizing high contrast, light-to-shadow ratio (4:6), intricate details, resolution, 4K, 8K, photos SHOT ON A LEICA M11 + SUMMILUX 50mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, --ar 4:6 --v 5 --style 4b" monochrome. chiaroscuro minimal highly detailed realistic.

a man opening the door of a vintage Citroën and getting in on a rainy Parisian backstreet. The man is holding a paper bag filled with vegetables. ((A stray cat, wet from the rain, looks up at the man from the ground.)) The man looks back at the stray cat. Minimalist street photography. emphasizing high contrast, light-to-shadow ratio (5:5), intricate details, resolution, 4K, 8K, photos SHOT ON A LEICA M11 + SUMMILUX 50mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, --ar 4:6 --v 5 --style 4b\" minimalist colors, chiaroscuro minimal highly detailed realistic.

Black and white photograph of a European city street on a rainy day, SHOT ON A LEICA M11 + SUMMILUX 50mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, street lamps hanging from an archway, trees and buildings lining the street, a person standing next to a parked car with an umbrella, blurred bicycle in the foreground, wet pavement reflecting the light, moody atmosphere, depth of field, vignette, slight motion blur. chiaroscuro high contrast

Black and white photograph of a European city street on a rainy day, SHOT ON A LEICA M11 + SUMMILUX 35mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows. 
street lamps hanging from an archway, trees and buildings lining the street, a person standing next to a parked car with an umbrella, blurred bicycle in the foreground, wet pavement reflecting the light, moody atmosphere, depth of field, vignette, slight motion blur.

Rue de Rivoli, Paris, France, on a rainy day, with a bicycle in the foreground, a person attempting to open a car door, and wet pavement reflecting the light, with trees and buildings visible in the background.
SHOT ON A LEICA M11 + SUMMILUX 35mm F/1.4, + extremely detailed depiction, sharpness, detail + professional lighting, noir, cinematic, deep shadows, 
Style: Photorealistic, Black and White Photography
Lighting: Overcast, wet reflective surfaces
Composition: Medium Shot, Slight Low Angle
Details: Rainy day, wet street, person with umbrella, parked cars, bicycle in foreground
Quality: High Detail

prompt: "Tokyo street corner at golden hour, SHOT ON A LEICA M11 + SUMMILUX 35mm F/1.4, monochrome, minimalist, high contrast, intricate details, light-to-shadow ratio (2:8), faint sunset glow reflecting on buildings, dynamic silhouette of a person (walking or cycling), silhouettes of signs and wires, noir, cinematic, deep shadows, --ar 16:9 --v 5 --style 4b"
negative prompt : colorful, blurry, low contrast, overly bright, crowded, cartoonish

Paris café at sunset\\\" for a location-specific scene. chiaroscuro minimal street photography. ray tracing, ultrawide angle, highly photorealistic, highly detailed, high definition, 4k, 8k, photos taken by sony, photos taken by canon, photos taken by nikon, photos taken by hasselblad + incredibly detailed, sharpen, details + professional lighting, photography lighting + 50mm, 80mm, 100m + unsplash, MONOCHROME.

GPS_48.8566_2.3522, Paris café at sunset\" for a location-specific scene. chiaroscuro minimal street photography. ray tracing, ultrawide angle, highly photorealistic, highly detailed, high definition, 4k, 8k, photos taken by sony, photos taken by canon, photos taken by nikon, photos taken by hasselblad + incredibly detailed, sharpen, details + professional lighting, photography lighting + 50mm, 80mm, 100m + unsplash, MONOCHROME.

ARW_9101.SR2 + Very detailed description, kirisame drizzle falling like a fine mist, taken with Sony, details + Professional lighting, high contrast, light-dark ratio (3:7), photo lighting + 50mm, 80mm, 100mm + Unsplash. A scene focusing on a corner of Paris's old town. The wet cobblestone streets after the rain reflect a beautiful landscape, with dynamic silhouettes as a key feature. A single dog drenched in rain—the dog's expression is captured clearly. A parent and child walking with an umbrella. A minimalist street photo emphasizing the contrast between light and shadow. Ray tracing, ultra-wide angle, advanced photorealism, high resolution, 4K, 8K, monochrome. chiaroscuro dynamic close up dramatic cinematic

ARW_9101.SR2 + Very detailed description, sharp photos taken by Sony, details + Professional lighting, high contrast, light-dark ratio (3:7), photo lighting + 50mm, 80mm, 100mm + Unsplash. A scene focused on a corner of the old town of Paris. The wet cobblestone streets after the rain reflect beautiful scenery, with dynamic silhouettes as a key feature. A parent and child walking with an umbrella, a single dog drenched in the rain. A minimalist street photo emphasizing the contrast between light and shadow. Ray tracing, ultra-wide angle, advanced photorealism, high resolution, 4K, 8K, monochrome.

投稿者プロフィール

Akira_O

こんにちは、AKIRA Obataです。私はAI技術を活用して、独自のデジタルアートを創作するアーティストです。テクノロジーとクリエイティビティの交差点で、新しい表現の可能性を探求しています。『aigenart』は、私の作品やアイデアを世界に発信する場であり、AIがもたらす美しさや驚きを皆さんと共有したいと考えています。