I have this situation when photographing still life photos of e-commerce products, for example leather shoes or leather bags:
- Table with white paper as a white background.
- Two flash lights with umbrellas on each side at an angle of about 45 ° (triggered by the flash shoe trigger on the camera) adjust the power manually, no TTL.
- Canon 70D camera on tripod.
- Camera settings in "M": 35 mm, ISO 100, 1/160, f8.0, measurement mode: evaluation measurement. AWB Automatic white balance activated.
With these fixed settings, all images should have the same exposure regardless of the object in the image.
Instead, I get different exposures depending on the object I'm photographing:
- If the subject is large (such as 50% of the frame) and, for example, brown or dark blue, the general exposure appears darker.
- If the object is small (like 20% of the frame) and, for example, yellow or pink, the general exposure appears better illuminated.
- I have some cases where there is a big exposure difference for everyone despite fixed settings.
I've been facing this problem for a long time and am fixing it in post production with Camera Raw. I researched and tested on the camera with various settings to understand why it works, but I can't figure it out
It looks like there's some kind of auto exposure that I can't control or that I can't find in the camera settings.
Unfortunately I cannot add an example because I cannot publish the product photos.
I would like to know whether it is possible to achieve the same exact exposure results with precise camera settings without the camera performing an automatic exposure (or similar).
EDIT: I cropped the same area on two different images with the same settings overall, but as you can see, the white background, which should be gray, is darker and lighter. It is not a shadow because the more or less brightness also affects the object itself. Overall, the picture looks brighter or darker.
The black areas are the objects that I had to delete because I cannot view or publish them.
EDIT2: When examining it in Adobe Bridge, I found a very strange thing, even if the settings for both images in the metadata are f8.0 1/160 ISO 100 35 mm. The Exif data says: 24 mm maximum value f / 3.8 for the first image, maximum value of 135 mm 1: 5.7 for the second image. This is pretty strange … is it possible that there is a hardware error in the lens sensors?