Photo Paper Background Colour Continuity

[d_natale]

<p>Hello,<br>

I'm currently photographing clothing for an online store, and I'm having problems with getting the same background colour each time. I'm using a Canon 5D with 50 mm 1.4 lens, 2 Bowen lights, one with a softbox and the other with an umbrella.<br>

I would like to have the exact same shade of grey for each photo, so that when they are up beside each other on our site, everything looks uniform. The difference is not huge, but enough that I would like to try to make everything a little more even.<br>

I shoot in raw, and when I edit the images I always set the white balance to the same settings. Does anyone know of a way in Photoshop to manually match the background colours? I also think that the clothes themselves might be reflecting some of their colour onto the background, but I don't know if there is a way to prevent that.<br>

Thanks in advance for the help<br>

<img src="http://farm9.staticflickr.com/8468/8427020140_351f6de651_b.jpg" alt="" width="1024" height="429" /></p>

[Matt Laur]

<p>How are you metering? How close are the subjects to the background?<br /><br />More importantly: with only two lights, how are you actually using them? The real way to solve such problems is to light the backdrop separately from the subject. The greater the distance you have between subject and background, the more you can independently control the way each is lit. More lights will also allow you to introduce a big of rim/hair lighting so that subjects like the girl on the left don't have their skin (like on her camera-left arm) come so perilously close to melting into the background. More lights, more separation and control. <br /><br />In the meantime, though: safe to say you're not using any sort of auto ISO control, and are manually setting shutter speed and aperture along with the WB you mention? Is there any other source of ambient light that's polluting the scene at certain times of day? </p>

[d_natale]

<p>Hey Matt,</p>

<p>The subjects are quite close to the background, but that can't really be changed, as the space I'm working in is very tiny and I can barely fit the lights in as it is. There is some other light coming in from the window , for instance, but this is also something that I can't change for the moment. <br>

re: ISO and so, yes, it's always set manually. Metering is set to evaluative and white balance is set to Flash. But regardless I am always using the set White balance / tint of 4400 / -4 when I open them in Photoshop.<br>

I'm looking more for a workaround in Photoshop I suppose. Thanks for your help</p>

[Matt Laur]

<p>I would skip the evaluative metering, and use enough light to make sure that an entirely manual exposure will be dead on every time. Otherwise, the camera is going to be moving the exposure up or down based on its attempt to push your subjects to middle grey. So, a subject in darker clothing is going to (using automated metering) cause the camera to overexpose, and a subject in lightly toned outfit is going to case under exposure. The only way to be consistent is to ... be consistent. For after-the-fact expure repairs, you're probably going to have to eyeball it.</p>

[d_natale]

<p>Would you recommend using spot metering then? I've actually never tried this before (I'm self taught, so I still have a lot to learn). And what do you mean by "enough" light? The exposure is set at a constant 1/125. Thanks again for the tips</p>

[Matt Laur]

<p>What I'm recommending is that you get the light and exposure set up <em>once</em> and don't change it. Basically, <em>no metering</em>. You don't want the camera having anything to say about how bright or dark to make the image. Take control of the situation by fixing the ISO, the aperture, and the shutter speed at values you won't change, so that your results are totally consistent from shot to shot. <br /><br />The "enough light" part refers to the lights you're using to create the scene. When your lights bring enough light to the set so that small changes in the ambient light (say, from that window) make no difference, you know you're adding enough light to keep consistently shooting for the same results. If the window light's varying brightness is overpowering the lights you're using, you can see how that would cause your results to vary as the daylight varies. So, block off that window, if that's the case. Use cardboard if you have to - just get creative.<br /><br />The metering part: sure use the camera's meter to get you in the neighborhood ... but once you see that it's at 1/125th of a second, note what aperture it's deciding to use. Because if you've set ISO, and set shutter speed, the only thing the camera's metering system can change is the aperture, based on how much light it sees reflecting off of what you're metering.<br /><br />And there's the problem! Different clothing reflects different amounts of light, and the camera has no idea if the clothing is white, black, or grey. So it tries to make <em>all</em> of them grey. But you know better, which is why you want to set the exposure mode on the camera entirely to grey, and then - along with your chosen ISO and shutter speed - also set aperture manually. <br /><br />This is where it gets a little tricky, because there are two things you have to think about.<br /><br />1) The exposure, of course. If you stop the lens down too far (say, f/16 or something) you're going to go dark - just not enough light making it into the camera. If you open up too far (perhaps f/2.8 would be just too fast, and you're going to blow out the highlights). Somewhere in your range is going to be an aperture that puts your middle-grey subject material right in the middle of your camera's histogram display, where grey looks like grey, black looks like black, and whites look like white without losing frabric details and whatnot. <br /><br />Don't evalute that on the back of the camera! Test exposures by displaying them on the computer using a calibrated display so you really know what you're getting.<br /><br />2) Depth of field. If you open the lens up too far (say, f/4 or more, like f/2.8) you're going to find it impossible to get all of your subject in focus. In the extreme, say while you're using a fast prime lens at f/1.8 or such, you're going to get noses in focus and ears out of focus. <br /><br />Likewise, if you stop down too far (f/16 or something worse - though you probably don't have enough light for that) you'll have tons of DoF, but will lose sharpness to lens diffraction. In real life you probably want to be around f/8 or so. But your ability to do that will depend on your light source, and whether you can get away with that. <br /><br />So, this comes down to some experimentation. But what you don't want are variables that change while you're shooting. So, eliminate varying light pollution from things like windows, and eliminate the camera's attempts to "fix" the exposure by using its metering in an attempt to guess how each subject should be handled. Once you've got it dialed in right, the light is the light, and your range of clothing will look more like what it really looks like, with no variations in the perceived brightness of the background.<br /><br />On the matter of the clothing colors reflecting light onto the background - if you have to, use post production tools to mask around your subject, and then simply desaturate the background so that there's no hue to it at all. That can get a bit tedious, but it sounds like you have no way to shoot with more space behind your subjects. Remember also that if that window light is playing a role, the color temperature of the light coming in through the window is going to cast colors on your background. Same solution there: block that window!</p>