22 | Don't make dappled sunlight look like polka dots. Background photo prompts created using distance differences, penumbra, and overlapping | Airi-chan
Target Audience
People who want to create summery background images with dappled sunlight
People whose AI image lighting turns into white polka dots or regular patterns
People who want backgrounds for X, note, Instagram, or EC advertisements where they can place text or products
People who want to design light and shadow as adjustable variables rather than atmospheric terms
What you will gain from this article
In this article, we will not specify dappled sunlight merely as a "round light pattern," but will break it down into the following three elements for design.
Light source
Distance to the leaves blocking the light
Wall or floor where the light is projected
Furthermore, we will parameterize the shadow contours, penumbra, shape and density of light spots, negative space, and projection direction.
By the time you finish reading, you will be ready to use natural language prompts, as well as JSON and Jinja2 templates, that can be adapted for product photo backgrounds, note banners, portrait-style backgrounds, and seasonal social media assets.
Introduction
"Beautiful dappled sunlight on a white wall"
Even if you just write it briefly, you can generate a decent-looking image.
However, if you look closely, you may find that round lights of the same size are lined up at equal intervals, looking more like a polka-dot pattern than dappled sunlight.
If you try to make it more natural by darkening the leaf shadows, they end up looking like shadows cut out of black paper. If you add green, the entire wall might end up dyed green.
Ah, I can see where to fix it now.
The problem is not that there is "not enough dappled sunlight," but that all the leaves are being treated with the same distance, same shape, and same density.
Natural dappled sunlight has contours that change depending on the distance to the leaves and branches, the overlapping of leaves, the direction of the light, and the angle of the projection surface. Therefore, this time, instead of increasing the light, we will separate the shadow layers.
Why it turns into a polka dot pattern
In image generation, terms like "dappled sunlight," "round light," or "light filtering through leaves" can sometimes be simplified into regular, bright circles.
There are four main causes.
1. Specifying light spots as circles
Writing "round light" makes it easy for perfect circles or ellipses to repeat.
Natural light spots have shapes that are partially cut off, overlapped with neighboring shadows, or elongated. You need to not only forbid circles but also specify the shapes to use instead.
2. All leaves are at the same distance
The closer the leaves blocking the light are to the projection surface, the easier the shadow shapes are to read. In areas where distant leaves or multiple leaves overlap, the outlines become softer.
If you make everything have the same outline, it looks like a stencil or a paper cutout.
3. Shadow density has only one level
With only pure white light and pure black shadows, it looks like a pattern pasted onto a wall.
By leaving thin penumbras and overlaps of varying density between the umbra and the bright areas, you create the feeling that the light has traveled through space to reach the wall.
4. Covering the entire wall surface
If you try to make the dappled sunlight the main subject and spread the shadows across the entire screen, it becomes difficult to use as background material.
It is important to separate the space for placing headings, the space for placing products, and the space for showing the light.
Design intent for this project
This example is a summer background material where products or text can be added later.
The composition was divided as follows:
Left 35%: Bright negative space for headings
Upper right to lower center: Dappled sunlight and leaf shadows
Bottom right: A low stone pedestal where products can be placed
Bottom: A warm sand-beige floor
The dappled sunlight consists of three layers: distant leaves, mid-distance leaves, and near leaves.
Distant leaves create large, soft shadows. Mid-distance leaves create shadows with slightly readable outlines. Near leaves were specified as small, partially clear shadows.
Even within the same shadow, I mix soft parts with slightly clearer parts. Not making the outlines uniform leads to natural fluctuations.
Explanation of the example image
The example is a vertical 4:5, 1122x1402 pixel image.
On the left side of the lime plaster wall, there is a large, bright blank space. Dappled sunlight flows diagonally from the top right to the bottom center, connecting to the floor at the bottom and the stone pedestal at the bottom right.
The light spots are not arranged as circles of the same size. I mix large blurred bright spots, small chipped bright spots, and elongated bright spots.
The shadows are also not just one level. I focused on soft shadows where the fine grains of the wall are visible, and made the outlines slightly clearer in only some parts.
Since products are not included directly in the generated image, you can composite cosmetics, food, miscellaneous goods, books, accessories, etc., later.
First, try generating just one image with only the background.
Separating the main subject from the background makes it easier to swap products or expand to different sizes.
Complete natural language prompt
用途はX、note、Instagram、EC商品画像へ使う夏の背景素材。縦型4:5、文字なしのフォトリアルなエディトリアル背景写真。
完全に架空の静かな屋内スタジオ。背景は、微細な砂粒と淡い色むらが残る温かなオフホワイトの石灰プラスター壁。壁より少し濃いサンドベージュのマットな床を下部へ置く。画面右下には、低い長方形の淡い石灰岩台座を配置し、台座の上面は画面全体の約12％だけ見せる。画面左側35％は、後から見出しや短いコピーを載せられる低情報量の明るい壁として空ける。
画面外右上の午前9時ごろの太陽光が、距離の異なる広葉樹の葉群を通過し、壁、床、台座へ木漏れ日を投影する。葉や枝そのものは画面へ入れない。
葉影を3つの距離層へ分ける。遠い葉は大きく柔らかな低コントラストの影。中距離の葉は中程度の大きさで、輪郭の一部が読める影。投影面に近い葉は小さく、部分的に少し明瞭な影。同じ影の中にも、柔らかな輪郭、少し明瞭な輪郭、細い半影を混ぜ、すべてを同じ硬さにしない。
明るい光斑は完全な円にしない。楕円、細長い形、途中が欠けた形、隣の影と重なった形を混ぜる。大きさを変え、2〜4個ずつの疎な群に分ける。群と群の間には広い間隔を置き、等間隔の反復を避ける。
木漏れ日と葉影は、壁の右上から中央下へ斜めに流れ、壁面の約30％だけを覆う。床と台座には、壁より少量の光斑を連続させる。左側の見出し用余白には目立つ影を入れない。
明るい光斑だけをわずかに温かなアイボリーへ寄せる。葉影は低彩度のニュートラルグレーから淡いグレージュ。壁全体を緑色に染めない。白飛びを避け、石灰プラスターの粒と色むらを明部にも残す。
壁へほぼ正対する50mmレンズ風。自然な遠近感、f/8相当、現実的な晴天の露出。石灰プラスターの微細な粒、石台座のごく小さな孔、自然なセンサー粒子を残す。実在するスタジオで自然光を撮影したような、静かで非演出的な写真。
人物、手、商品、植物本体、見える枝葉、窓枠、家具、文字、数字、ロゴ、ブランド、透かし、完全な円、同じ大きさの丸、等間隔の水玉、規則的な格子、レース模様、硬い黒影、葉の輪郭をそのまま写し取った切り絵、緑色の全面かぶり、夕焼け、強いレンズフレア、過度なHDR、光の筋、煙、霧、CG、3Dレンダーは入れない。JSON format variable example
{
"use_case": "X・note・EC商品画像向けの夏の背景素材",
"asset_type": "フォトリアルなエディトリアル背景写真",
"aspect_ratio": "4:5 vertical",
"location": "完全に架空の静かな屋内スタジオ",
"background_surface": "微細な砂粒と淡い色むらが残る、温かなオフホワイトの石灰プラスター壁",
"ground_surface": "壁より少し濃いサンドベージュのマットな床",
"pedestal": "画面右下に置く低い長方形の淡い石灰岩台座、上面は画面の約12％",
"negative_space": "画面左側35％を低情報量の明るい壁として空ける",
"light_source": "画面外右上の太陽光が、距離の異なる広葉樹の葉群を通過する",
"shadow_layers": "遠い葉の大きく柔らかな影、中距離の中程度の輪郭、近い葉の小さく少し明瞭な影の3層",
"light_patches": "楕円、細長い形、欠けた形が混ざる不規則な光斑。大小を混ぜ、2〜4個ずつの疎な群へ分ける",
"coverage": "木漏れ日と葉影は壁の右上から中央下へ斜めに流れ、壁面の約30％だけを覆う",
"edge_behavior": "同じ影の中でも輪郭の一部は柔らかく、一部は少し明瞭。細い半影を残す",
"lighting": "午前9時ごろのやや温かな自然光。明るい光斑だけを少し暖色にし、影は低彩度のニュートラルグレー",
"camera": "壁へほぼ正対する50mmレンズ風、自然な遠近感、f/8相当、白飛びを抑えた露出",
"texture": "石灰プラスターの微細な粒、台座のごく小さな孔、自然なセンサー粒子",
"constraints": "人物、商品、文字、ロゴ、水玉、規則模様、硬い黒影、切り絵、緑かぶり、HDR、CG、3Dを除外"
}Jinja2 template
用途：{{ use_case }}。{{ aspect_ratio }}、文字なしの{{ asset_type }}。
{{ location }}。背景は{{ background_surface }}。床は{{ ground_surface }}。{{ pedestal }}。構図は{{ negative_space }}。
光源は{{ light_source }}。葉影は{{ shadow_layers }}。光斑は{{ light_patches }}。配置は{{ coverage }}。輪郭は{{ edge_behavior }}。
照明は{{ lighting }}。{{ camera }}。質感は{{ texture }}。実在の撮影スタジオで自然光を撮影したような、静かで非演出的な写真。
禁止事項：{{ constraints }}。Replaceable variables
`background_surface`
Can be changed to lime plaster, Japanese paper, unbleached cloth, light mortar, wood, or sandstone.
When changing the background, specify only one type of surface grain, fiber, texture, or wood grain. Mixing too many materials will dilute the visual impact.
`pedestal`
You can change it to a stone pedestal, wooden pedestal, translucent acrylic, or no pedestal.
If you plan to place the product later, it is easier to use if the surface area of the pedestal top is 10-18% of the screen.
`negative_space`
You can change it to 35% left, 35% right, 30% top, or a plain area in the center.
Do not include the text itself during generation; specify only the low-information area where the text will be placed.
`shadow_layers`
Three layers is the standard; you can increase it to two layers for a soft background or up to four layers for photographic works.
Increasing the number of layers does not necessarily make it more natural. Limit it to a range where the differences can be perceived.
`coverage`
The guideline is 20-35% for background materials and 40-60% for photographic works.
Even when increasing shadows, fix the necessary margins for your intended use first.
`lighting`
You can change it to warm morning light, neutral midday light, or low, slanted light from late afternoon.
Even when shifting toward evening, do not make the entire surface orange; only make the highlights slightly warmer.
Derivatives by use case
Cosmetics/Beauty EC
Expand the stone pedestal in the bottom right to 15% of the screen, leaving the top left as a margin for copy. The wall is a bright ivory, and the shadows are a pale greige. If placing a glass container later, keep the pedestal's reflection low.
Food/Gifts
Change the pedestal to light-colored wood and make the light spots slightly warmer. It is easier to swap out if you do not generate the food directly and instead process the background and the product separately.
note/blog banner
16:9. Leave 55% of the left side of the screen as blank space, and gather the dappled sunlight on the right 45%. Remove the pedestal, assuming the title will be added later.
Portrait background
Lower the contrast of the shadows and do not place prominent light spots in the upper center where the person's face will be. Design the person as a completely fictional adult, separate from the background.
Derivatives by composition
Left-margin type
Shift the main shadow from the top right to the bottom right, leaving 35-45% of the left side open. Suitable for product advertisements and note headings.
Right-margin type
Flow the light from the top left to the center and move the product pedestal to the bottom left. Suitable for layouts where vertical text or short copy is placed on the right side.
Top-margin type
Gather the pedestal and shadows in the bottom half, leaving the top 35% as a bright wall. Suitable for Instagram and announcement images.
Full-frame artwork type
Remove the pedestal and increase the dappled sunlight to 45% of the screen. However, leave space between the clusters and do not fill the entire surface with patterns.
Derivatives by size and aspect ratio
4:5: X, Instagram, and examples within note articles. Makes it easy to show the pedestal and vertical light
1:1: Gather the dappled sunlight in the top right quarter and make the pedestal smaller
16:9: Use 55% of the left side for text margin and 45% of the right side for dappled sunlight
3:2: Product photos, blogs, and printed materials. You can increase the floor area to 20-25%
Derivatives by color scheme
Ivory x Greige
The basic color scheme for this time. It can be widely used for cosmetics, food, and lifestyle.
White x Pale Blue-Gray
Suppress the warm colors of the light spots and turn the shadows into a light blue-gray. It is suitable for refreshing summer materials and hygienic product backgrounds.
Beige x Olive Gray
Make the wall off-white and add a very small amount of olive to the shadows. It is important not to make the entire wall green.
Pale Pink x Warm Gray
For beauty and gifts. Make the wall surface a low-saturation pink-beige, the light spots ivory, and the shadows warm gray.
Failure examples and correction prompts
Failure 1: White polka dots are lined up at equal intervals
The cause is that the shape, size, and spacing of the light spots are uniform.
壁、床、台座、余白は維持する。完全な円、同じ大きさの丸、等間隔の反復を除去する。光斑を楕円、細長い形、途中が欠けた形へ変え、大小を混ぜる。2〜4個ずつの疎な群へ分け、群と群の間に広い間隔を作る。Failure 2: Leaf shadows become black paper cutouts
The cause is that all leaf shadows have the same hardness and density.
構図と光の方向は維持する。硬い黒影と葉の輪郭を写し取った切り絵を除去する。遠い葉の大きく柔らかな影、中距離の中程度の影、近い葉の小さく少し明瞭な影へ分ける。明部と暗部の境界に細い半影を戻す。Failure 3: The entire wall becomes green
影の位置と壁の質感は維持する。壁全体の緑色かぶりを除去する。壁を温かなオフホワイト、光斑をアイボリー、影を低彩度のニュートラルグレーへ戻す。オリーブ色は影の一部へごく少量だけ残す。Failure 4: Shadows cover the entire screen, making it impossible to place text
台座と壁の色は維持する。木漏れ日と葉影を壁面の右側30％へ縮小し、画面左側35〜45％を低情報量の明るい壁として空ける。余白内へ大きな光斑や濃い影を入れない。Failure 5: The wall becomes smooth CG
光、影、構図は維持する。均一で滑らかなCG表面を除去する。石灰プラスターへ微細な砂粒、淡い色むら、ごく浅い塗り跡を戻す。強い凹凸、汚れ、大きなひび割れは追加しない。白飛びを抑え、明部にも表面の粒を残す。Prohibited items
Do not arrange perfect circles or light spots of the same size at equal intervals
Do not make leaf shadows uniformly hard black
Do not use paper cutout expressions that trace the outlines of leaves as they are
Do not dye the entire background green or orange
Do not add strong shadows to the margins for text
Do not mix products, brands, or logos into the background image
Do not recreate actual stores, homes, or studios
Do not include strong lens flares, light rays, smoke, fog, or excessive HDR
Do not use perfectly smooth CG walls or plastic pedestals
Summary
You don't need to increase the number of light circles to make dappled sunlight look natural.
What you need is to separate the distances to the leaves, vary the outlines of the shadows, break up the shapes and spacing of the light spots, and prioritize the margins needed for your intended use.
I see the image now!
At first, try changing only the two items 'shadow_layers' and 'negative_space', and compare one soft background and one background for product advertising. By limiting the changes, it becomes easier to judge which specifications contributed to naturalness and usability.
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