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Hi Guys,
I found this little frog tonight on our driveway, and took him into the light tent to shoot with an isolated white background. I used white card curved as the backdrop, to create a featurless, white background, and then used a slave flash to the right at 1/16 power, the on camera flash was also firing at 1/16 power and exposure was 50th of a second at f/9 at ISO 100.

I have always wanted to get those perfect backgrounds in lighttents where I am getting a pure 100% white background when I shoot. I am never sure how to do it though. I would extract onto a white background, but do not know how to extract an object with a blurred edge such as this frog.

How do you shoot in a light tent and get a 95-100% white background, if this is impossible, how do you extract an object in photoshop if it has an out of focus/blurred edge?
Cheers
Brooke

This is one of the shots that I took:

Full size jpeg download link: in case anyone wants to have a go at extraction for examples:
http://www.brookewhatnall.com/webdisk/frogfull.jpg

The darker-than-white background is caused by light falloff. In other words, the background is underexposed.

One easy remedy is to use a separate light for the background. This will give you a white background as well as providing contrast to the subject.

Ok ...

A couple of housekeeping issues first.

Although you seem to be asking about a technique, it still comes down to looking at this image and seeing how it may be improved. Consequently I've moved this image into the image critique section.

On the subject of looking at the image, this site is designed to view images that are no greater than 800px along any side, and also for those images to have a small-ish file size. That permits everyone to download and view the images in comfort. View the WHOLE image. While you've nailed the filesize, this image is way too big to be viewed in full. You will do better in terms of getting responses to your questions if you would review and adjust this aspect.

Getting to the image: you're shooting close and personal here, and for that, you need to have a lot of depth of field. The frog, shot from head on, is a sort of a deep animal, and here we can see that the DoF is quite shallow: the eyes appear sharp, but not the mouth, nor the body.

To get a lot of DoF, you need a small aperture (small hole, high number), and that in turn translates to lots of light. With a light tent, you usually need two, perhaps even three or four light sources, and you also ned to try to direct the light to where you need it to be.

For instance, for this image, I would have used at least three lights. One of those would have been placed to each side of the light tent, and in a plane between the frog and the camera, and a little above the level of the frog, pointing down. These would form the primary light source that's illuminating the frog, and I would have these lights dialled up so that I'm using a good aperture: minimum target would be around f/13-f/16, depending upon the glass, focal length, and the lens's sweet spot.

Remember that as you move out of the lens's aperture sweet spot, you will lose sharpness. That may or may not be significant, depending upon the lens.

Having set those two plights as the main, I would then add an extra light (or maybe two) behind the frog. If just the one, I might place it behind the frog, above the tent, pointing towards the rear of the tent, or I may place it directly behind the tent, facing forward, directly toward the rear surface of the tent. I would probably dial this up by about 1.5 - 3 stops higher than the primary light source, in order to totally blow the background. If this light is above the tent, be sure to use something to direct the light slightly away from Kermit, so that you don't get too much bleed from this light onto areas that you want this light to be: this light's purpose is solely to illuminate the background.

Let's now look at your settings for this shot: 1/50, f/9, ISO 100, on camera and slave flash at 1/16 power.

First of all, shutter speed is largely irrelevant for this shot. You're shooting with flash, and consequently, it's your flash settings that will be driving this exercise. As long as you have a shutter speed that syncs with the flash, it basically makes no difference. With most DSLRs, anything from 1/30 to 1/200 will work. Your actual exposure shutter speed will actually have been something like 1/10000 .... truth be told.

So ... let's now look at at your flash settings aperture. These are intimately involved with one another, so this is adults' only stuff.

Note that earlier I said that you'd need greater depth of field, which also means more light. f/9 and 1/16 power isn't really doing the job. STart with aperture at f/16, set your slave flash to 1/4, leave the on-camera flash at 1/16 (it's only use here will be as a trigger) and try that as your starting point.

Are they the only light sources that you have? If so, washing out the background isn't going to happen easily. If you have other lights, then set them up using the techniques I've described, and see how it goes.

And FWIW, you don't need Kermit as the model. Buzz or Woody will do well in these sorts of tasks.

What Trevor has said is spot on. To rescue the pic posted (I hope you don’t mind - can remove) I took it into PS, levels and then used the white pointer on the white area(!) to obtain this result:

In photoshop or PP program, increase your level or exposure so that white is white...

And oh, did someone figure out white balance has to do with how white looks like... white?

Hi Brook,
great question/s and the answers provided have given me a few reminders about technique (thanks team) .
I can only encourage you to practice and start collecting light sources - I now use 3-4 of those cheap clip on bed lights when I get the tent out so I can really control the shadows and find it makes a huge improvement. Also worth doing a White balance check on your set up as the globes chosen make a world of difference - recommend setting a custom WB if your camera permits - I find it helps me a lot.
Seperating anything out in PS is a skill in itself and is easier if DOF gives crisper edge ... so look for the feathering edge option - recommend you hunt the web for free tutorials (I have some somewhere so will have a hunt )

But nice frog and a great start ..
Deb T

I tried to make a temporary light tent last night, using an upturned chair and a white satin sheet (the chunk of sheet that I bought for backdrops - not that it has been of much use). Lighting with my SB-800 on one side and my SB-600 on the other (both with diffuser caps) and the fluro that is the main light for the kitchen (not sure how much effect it had) and then using the pop up flash to trigger I got quite nice results, but with the same grey background (kicking myself for not doing a custom WB for it - next time) but using the white point in Capture NX2 fixed it instantly.

Now I want a light tent!!