A digital image takes on a film-like quality when grain is added. This process requires some care. Whether for the web or print, the grain must be adjusted to suit the output size. Testing is essential.
Grain is inherent to film photography. Its visibility depends on the image’s magnification ratio on the print. Let us consider a practical example: “Martinique” by André Kertész, taken on January 1, 1972. The photographer used 35mm film. The image is cropped, with grain clearly visible on a medium-sized print such as the one in the Center Pompidou’s collection: image size 19 x 24.8 cm. On an enlargement like the one at the ICP, where the image measures 39.1 x 49.8 cm, the grain is indeed more pronounced.
Film grain: a matter of enlargement
Around the same time, the American photographer George Tice (1938–2025) used an 8×10-inch (20.4 x 25.4 cm) view camera with Tri-X Pro film, rated at ISO 320. His prints are enlarged only slightly, most often to 40×50 cm, which explains the absence of visible grain, even though their structure is similar to that of the film used by Kertész. In a print, the larger the enlargement, the more visible the grain becomes.
When viewed at a small size, this photograph, taken on TMAX 400 film in 24×36 format (Leica M4-2 and Zeiss ZM 50 mm Planar lens), shows no grain. On a 1.5-meter enlargement, a detail of which is shown on the right, the grain is clearly visible.
Digital Grain: It is All About the Balance
When you add grain to a digital image to give it a film-like look, regardless of the software used (DXO FilmPack, Lightroom, Nik Silver Efex), the appearance varies depending on three factors: the image’s pixel count, the amount of grain applied, and the image’s intended use. The same amount of grain applied to a 4000 x 6000-pixel image or a 1000 x 1500-pixel image will result in a different grain pattern on a 10-cm-long print.
You must therefore adjust the grain to suit the print and apply it last, depending on the desired look. In Lightroom and Photoshop (Grain layer), grain is controlled by three sliders. Amount controls the overall intensity of the grain. Size adjusts the size of individual grain particles. Sharpening alters the randomness of the grain, resulting in a smoother or rougher appearance.
The original image size is 4000 x 6000 pixels (taken with a Nikon D600). A copy is exported at 1000 x 1500 pixels.
The same noise setting is applied to both images in Lightroom, and the noise is intentionally emphasized. When comparing the grain effect viewed at 100%, it appears different depending on whether it is applied to the 24 MP image or the 1.5 MP image. In the high-resolution image detail (on the left), the grain is soft, whereas in the low-resolution version, it is better defined and sharper.
Internet and Social Media
If the image is intended for social media, such as Instagram, the recommended resolution is 1080 x 1080 pixels. First, export the image at this resolution, then add grain, adjusting the amount based on the desired effect.
Upload the image to the platform and check if it looks right.
For a website, the issue is more complex due to the variety of screen resolutions. Most websites today use responsive design. A Full HD image filling the entire surface of a UHD screen (3840 x 2160 pixels) appears less sharp due to display interpolation.
The grain is diluted. Balancing its presence in post-production is therefore a matter of compromise between the appearance of the grain on a “pixel-for-pixel” display (1 pixel in the image = 1 pixel on the screen) and an interpolated representation.
On social media platforms, such as Instagram, upload the image to a phone or tablet to check that the grain size is appropriate.
The process is similar for a website. When creating a page or adding a photo to a gallery, you can immediately check the screen to ensure the grain setting is satisfactory.
Resolution and Printing
When it comes to printing, the challenges are different. Each type of printer has a specific dot resolution—the resolution at which the image’s pixels are converted into ink droplets. For example, on Epson printers up to A2 size, this resolution is 360 ppi. The printer driver automatically interpolates a file with a resolution different from these values.
For grain to be printed without loss of sharpness or structure, it must be incorporated into a file with a resolution identical to the print resolution. Let us take the example of the opening image from a Nikon Df, which is 4928 x 3280 pixels. If we print it at 40 x 60 cm, the file resolution is 4928 pixels/60 cm, or 82.13 pixels/cm, or 208.62 pixels/inch. If I apply grain to this file, it will be slightly distorted by the resolution interpolation, which will increase from 208.62 to 360 ppi in the print driver.
It is therefore better to resample the image to 360 ppi before applying the grain. This way, it will be rendered clearly on the print, as there is no interpolation. That said, the grain size will need to be determined on a case-by-case basis, depending on the desired texture. Testing is essential. There is no magic formula. Print at the desired size and adjust the grain in the software if it appears too strong or too weak.
A Nikon Df file is 4928 x 3280 pixels. Without resampling, at a resolution of 360 ppi—which is the native resolution of an Epson A3+ or A2 printer—the print size is 34.77 x 23.14 cm.
Without resampling, a 60-cm-long print has a resolution of 208.62 ppi. The driver for an Epson A3+ or A2 printer interpolates the image to 360 ppi. If grain has been added to the file, the interpolation slightly blurs the grain.
When resampling to 360 ppi for a 60 cm-long image, the interpolation inevitably blurs the file slightly, since new pixels are artificially created to enlarge the image. However, the grain, which will be added to this new 360 ppi base, will give the image a distinct texture.
The grain is adjusted to suit the output size. At 100% on-screen, the grain may appear excessive, but it will be less noticeable in print. Test prints are necessary to determine the desired look. The principle of adding grain remains the same with other software: Lightroom grain, Nik Silver Efex, etc.
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The long courses to become professional photographers allow you not only to master all the photographic techniques and its vocabulary (blurs, hyperfocus, sharpness zone, depth of field, backlighting, focal length, shutter release, autofocus, wide-angle, rule of thirds, etc.), but also all the stages of shooting and image processing.
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Text and photos: Philippe Bachelier, teacher of Printing techniques at Spéos