One Grey Card Frame Can Fix Colour Across a Whole Product Shoot

A silver ring photographed under the same studio setup should not look blue in one image, grey in another and slightly yellow in a third. Yet automatic white balance can react differently as the product angle, reflections and background change.

That inconsistency matters before AI enters the workflow. If the source photograph has the wrong colour cast, a colour-variation or lifestyle-image tool receives an unreliable reference. A neutral grey-card frame gives the editing software evidence of the light colour, so the same correction can be applied across the whole shoot.

This tutorial uses RawTherapee, a free, cross-platform raw processor. The method is for a series photographed under one unchanged lighting setup. It corrects capture colour consistently rather than recolouring the product.

What you need

Use a camera that can save raw files, a genuinely neutral photographic grey card and RawTherapee. A calibrated card is preferable to printer paper, packaging card or fabric because apparently white household materials can contain dyes or optical brighteners that are not spectrally neutral.

Keep the lights, modifiers, product position and surrounding room light stable. Turn off mixed sources such as a warm ceiling bulb when the product is lit by daylight-balanced LEDs. A grey card can measure one lighting condition, but it cannot make two different light colours behave like one.

Step 1: photograph the card under the product light

Place the grey card where the product will sit and angle it toward the camera. It should receive the same light as the product, not light from a different part of the table. Fill enough of the frame that the card contains a clean sample area, but avoid glare, deep shadow, printed text and dirty edges.

Take one raw photograph of the card before photographing the SKU. Remove the card and shoot the product without changing the lights or camera white-balance setting. If you move a light, change a modifier, switch rooms or allow daylight to change substantially, take a new grey-card frame for the new group.

Lock exposure when practical. Automatic exposure can still make one polished product brighter than another, even after the colour balance is synchronised. The card solves the colour of the illumination, not every difference in exposure or reflection.

Step 2: set the reference white balance in RawTherapee

Open the folder in RawTherapee and load the grey-card photograph in the Editor. In the Color tab, open White Balance and choose the Spot WB picker. RawTherapee’s official documentation explains that clicking a known white or grey area adjusts the image so the red, green and blue levels at that spot become equal.

Click near the centre of the card on an evenly lit patch. Do not sample a shiny highlight, the edge of the card or a visibly shadowed area. You can use the picker more than once until you find a clean patch that produces a sensible result.

The aim is neutral light, not a more dramatic photograph. Do not warm the white balance simply because warmer gold looks richer. Creative colour grading can be added later to campaign imagery, while the product master should remain a trustworthy record of the item.

Step 3: copy only the white-balance correction

Return to the File Browser. Right-click the corrected grey-card frame and choose Processing Profile Operations, then Copy. Select the product photographs from the same lighting group, right-click one of the selected files and use the partial paste option.

Choose White Balance only. RawTherapee processing profiles can be copied in full or in part, and its documentation specifically notes that partial profiles can transfer selected settings while omitting others.

Partial paste is important here. A full profile can also carry exposure, crop, sharpening, noise reduction or lens settings that may not suit every product frame. The purpose of this pass is to synchronise the measured colour correction while leaving unrelated decisions alone.

Step 4: review the set before exporting

Open several product frames after applying the correction. Compare the same physical material across angles. Silver should retain a consistent neutral character, and white packaging should not alternate between blue and cream. Gold and rose gold should remain distinct rather than being pushed toward one shared orange tone.

Check the grey card result, but also use your knowledge of the real product. Polished metal reflects its surroundings, so a blue highlight from a nearby wall can remain even when the illumination is correctly balanced. White balance is a global correction and should not be used to erase every coloured reflection.

If part of the shoot still looks different, ask whether the lighting actually changed. Separate those files into another group and use the grey-card frame recorded for that setup. Do not force one correction across frames shot under different light.

Step 5: queue consistent output files

When the set is approved, add the images to RawTherapee’s processing queue and choose the format required by the next step. Keep the raw files and their processing profiles as the editable masters. Export a high-quality TIFF or PNG when the files will undergo further retouching, compositing or AI work. Export final JPEG copies when that format suits the selling channel.

Do not overwrite the original raw captures. RawTherapee stores editing instructions separately from the source, so you can return to the measured white balance and produce a new output without repeatedly recompressing a JPEG.

Where this fits in an AI product-image workflow

Use the corrected real photograph as the approved reference for background generation, lifestyle scenes, angle generation or colour variants. The AI output still needs checking, but its starting reference is less likely to contain an accidental blue, green or amber cast.

Do not apply the same RawTherapee white-balance profile blindly to generated images. AI scenes may depict different lighting, and their pixels were not captured under the measured studio lamps. Instead, compare generated products with the neutral real master and reject results that change the verified material colour.

For jewellery sellers, this separation is especially useful. White balance can make a silver reference neutral, but it cannot prove that an AI-created gold variant has the right alloy hue, polish or reflection structure. Colour generation and colour calibration are related tasks, not the same task.

What a grey card cannot fix

A grey card does not create full colour accuracy by itself. Camera profiles, monitor calibration, light quality and the reflective behaviour of the product still affect what you see. A colour target with several known patches is more appropriate when exact branded packaging colours or gemstone hues must be measured.

It also cannot repair clipped highlights. If a polished edge is pure white with no recorded detail, changing white balance will not restore the missing information. Expose reflective products carefully and review the histogram before dismantling the setup.

The useful outcome is narrower and practical: one measured frame can stop automatic white balance from making each image in a product shoot look as if it was photographed under different lamps. That creates a more reliable catalogue and a better source for every AI derivative that follows.

Sources

RawTherapee, “About,” reviewed 3 October 2026: https://rawtherapee.com/

RawPedia, “White Balance,” reviewed 3 October 2026: https://rawpedia.rawtherapee.com/White_Balance

RawPedia, “File Browser” and “Batch Adjustments / Sync,” reviewed 3 October 2026: https://rawpedia.rawtherapee.com/File_Browser

RawPedia, “Sidecar Files and Processing Profiles,” reviewed 3 October 2026: https://rawpedia.pixls.us/sidecar_files_-_processing_profiles/