Achieving pure white background with continuous lighting

[ClickClick87]

Hi there

I take quite a few product shots at work but I'm struggling to get that crisp white background.

Although I'm confident with Light Room and Photoshop, I'd feel happier getting it done correctly in camera.

My set up is pretty basic...two continuous lights and a seamless backdrop.

I shoot in manual, set custom WB and often use exposure compensation to a point just before the product starts to blow out.

Does anyone have any advice on how to set up my lighting sources in such a way that it (to think of a better phrase) over exposes the background but not the product, for example, angles, position, distance from scene etc?

Perhaps my exposure triangle is slightly off, so would using aperture priority help?

 

[Phil V]

The starting point is that they need lighting separately.
Which then creates a question about subject distance as the white bg becomes a light source behind the subject.

The simple answer is that for small items, PP is the easiest way of getting a nicely lit subject and good white background.

 

[Garry Edwards]

Phil has summed it up very well - but in the hope that your employers may wish to dramatically improve the quality of their in-house product photography and reduce labour costs at the same time, I'm including some more detail.

The subject and the background are two separate subjects, which is why they need to be lit separately. The background needs to be lit brighter than the subject, by about 0.7 of a stop, to make it white, and this requires a minimum of one dedicated light source (for a very small subject) and up to four for a large subject, two is OK for most things. The subject needs to be lit in a way that shows it at its best, and so using one of just two lights for the background is bound to create serious lighting quality problems.

Some subjects can be lit with just one light, most require at least two, some need more.

So, if your employers want to get better photos and to minimise post processing work, which costs time and therefore money, they need to spend money on more lighting equipment. And if they want really accurate colour reproduction then they need to move to flash, continuous lighting can't do justice to many colours.

A lot of people, using enough lights and using them well, can and do get everything as right as it can be in camera, but most really high end product photography is shot with the background unlit and the subject is then cut out in PP - this takes time but produces better quality because white backgrounds bounce light where it isn't wanted, this affects the quality of the lighting and also reduces contrast, can create flare and also can degrade the edges of some subjects.

 

[ClickClick87]

Thank you both very much, two very insightful posts.

This has got me thinking...would a carefully placed silver reflector help bounce light back into the scene, resulting in brighter whites?

If so, would it be best to:

A) Project light directly onto the background and the background bounce this onto the reflector to indirectly fill the scene (or would the backdrop absorb the light)?

B) Project light directly into the reflector and let the reflector bounce light into the scene, including backdrop?

Ideally' I'd like a three or four light setup (two for the background, and two for the product) but reflectors may seem like a quick fix for now.

 

[KIPAX]

I shoot in manual, set custom WB and often use exposure compensation to a point just before the product starts to blow out.

There is no exposure compensation when shooting in manual ..

Just sayin...

 

[Garry Edwards]

Thank you both very much, two very insightful posts.

This has got me thinking...would a carefully placed silver reflector help bounce light back into the scene, resulting in brighter whites?

If so, would it be best to:

A) Project light directly onto the background and the background bounce this onto the reflector to indirectly fill the scene (or would the backdrop absorb the light)?

No, because
a. The light would seriously overexpose the background, creating flare, reducing contrast and degrading the edges of the subject.
b. By the time the light has reflected from the background, travelled to the reflector, lost some power in reflection (no reflector is ever anywhere near 100% efficient) and then bounced back to the subject, so much power will have been lost due to the effect of the Inverse Square Law that the difference in effective lighting power would be in the region of maybe 3-4 stops instead of the approx 0.7 stop difference that's needed.

B) Project light directly into the reflector and let the reflector bounce light into the scene, including backdrop?

Ideally' I'd like a three or four light setup (two for the background, and two for the product) but reflectors may seem like a quick fix for now.

No, again because of the Inverse Square Law. The background is behind the subject, therefore the light has to travel further to reach it, losing a lot of its power in the process.

 

[swanseamale47]

You've had the answer really. Light both as different subjects. The other way is to cut out your subject and create the background in PP, easy enough for a simple object using paths, trickier if it's something with fine detail on the edges like hair, but still usually do-able. Frankly the easy way is to just light it properly.
You can buy lights cheap enough these days,, a quick look on flebay shows two continuous lights with soft boxes for £25, Or a set of 4 video LEDs for around £70.