How can I whiten my background, without whitening the subject or modifying subject colours?

Question

If I take portraits against a white background I like to use a colorchecker passport to ensure that my subjects come out at the end of my workflow looking 'true to life'.

The problem is that due to whatever reasons, my white background sometimes comes out looking slightly grey.

Is there a way to whiten the background without interfering with the colour of the subject? I could just up the white level etc. but that would obviously apply to my subject as well.

I have PS and LR but prefer to use LR.

To add some clarity to this post: I am specifically asking about modifying the background colour in lightroom or photoshop whithout it applying to the subject.

Answer 1

You haven't talked about your lighting at all, but that's almost definitely where the problem is. Simply, the background needs to be lit independently of the foreground. You almost definitely need more space between subject and background (to avoid light spill) and depending upon subject size you may need several lights to evenly light the background adequately. Meter for the background and subject independently so that you can be sure enough power is being put out on the background to make it white.

Another problem -- though much smaller -- is likely that using the ColorChecker is working against you. The background is almost definitely not a brilliant pure white, so the color adjustments you're making are helping to bring that down to a more realistic almost-white. Again, lighting the background independently of the foreground helps solve this because you can be sure you're setting the flash output on the background to something that will ensure white is... white.

Answer 2

If the white balance and white point are correct, then the background should be displayed as white. If it isn't, then you are doing something wrong with your color target. If it is a good neutral grey, then the white balance is correct, but the white point is too bright. I would adjust the white point to bring the white point up to where it belongs.

It may also mean that you don't have enough light on the background if the subject has brighter highlights than the background itself (in which case it isn't going to be possible to get a white background without selective color replacement or matte painting). If the subject is more brightly lit than the background, then relatively speaking, the background would be grey.

If the background was too dark and the subject is too bright to bring up the white point overall, then you will need to mask out the subject so you can work exclusively on the background. If it's a fairly regular color, you can probably use the magic select to get a quick starting point. Once you have a mask for the background, you can apply an exposure correction or simply change the color of the background by itself.

Answer 3

if your background is bright and differs from your subject - try to use "Adjustment Brush" in Lightroom with "Auto Mask" enabled. Add some +1 or +2 to Exposure and brush out the background. "Auto Mask" will keep subject untouched.

Best option here is to use a photography technique to get isolated white background. Yes it is possible without playing in Photoshop.

The main point here is to over expose a background separately from a subject. You should be able to control your light. This way you will have control over a background and a subject.

Second important thing is to have a glossy white floor. In this case overexposed background will reflect from it and give also a overexposed floor. To make a subject completely isolated - you will need just to remove a reflection of a subject itself in a Photoshop or Lightroom, but I prefer to leave it as it is nice looking and can be removed easily if there are such needs.

Here is detailed tutorial on how to achieve this.

Achieving an Isolated White Background in a Home Photo Studio

Feel free to ask any questions

Hope that is helpful.

Cheers.