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DPChallenge Forums >> Hardware and Software >> What is it? and how does it work?
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 03/24/2004 07:56:46 PM · #1
//cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30079&item=3804794178

looks cool/cheap. How does it work? Do you need to purchase any other equipment? I already have a white sheet that works nicely. If anyone knows how these work, or has one, please, respond here. Thanks.
03/24/2004 08:03:34 PM · #2
Originally posted by hsteg:
//cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30079&item=3804794178

looks cool/cheap. How does it work? Do you need to purchase any other equipment? I already have a white sheet that works nicely. If anyone knows how these work, or has one, please, respond here. Thanks.


This is essentially the same process they use in TV to put a weather map behind the forecaster. They shoot the person in front of a green or blue background which gets filtered out (for want of a better explanation) and replaced by a graphic such as a weather map. I really don't understand the tech side of it. I'm sure someone will pipe up. :)
 03/24/2004 08:10:54 PM · #3
u think itd work with a white background? It appears to in the example picture on the page.
03/24/2004 08:11:21 PM · #4
Originally posted by hsteg:
//cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30079&item=3804794178

looks cool/cheap. How does it work? Do you need to purchase any other equipment? I already have a white sheet that works nicely. If anyone knows how these work, or has one, please, respond here. Thanks.


I would think you need a projector.
 03/24/2004 08:13:24 PM · #5
where do you get that idea from
?
 03/24/2004 08:17:21 PM · #6
Originally posted by hsteg:
where do you get that idea from
?


I guess it's like a filter. Something that is applied to the background. Not much info.
 03/24/2004 08:18:43 PM · #7
I think they are just backgrounds...just a plain background on your computer. To get your model there, you will have to cut and paste your model and manually put it on the background.
 03/24/2004 08:23:43 PM · #8
I dunno. I wonder if someone actually has it.... I emailed the seller, waiting for a response from them...
 03/24/2004 08:28:03 PM · #9
Originally posted by hsteg:
u think itd work with a white background? It appears to in the example picture on the page.


Very often in product photography this is exactly what is done. The background is lit so that it is "blown out", which makes it easy to extract a (darker) subject. If the subject is very light, you can use a jet-black background. You then use Photoshop to extract the subject and place it over the new background. It takes a bit of knowledge and experience to get it right.
IMO it's easier to shoot it with a good background to begin with.
 03/24/2004 08:51:44 PM · #10
and a lot more expensive.
03/24/2004 08:56:42 PM · #11
Originally posted by hsteg:
and a lot more expensive.


Well, not necessarily. I'm a big fan of candids in natural light, so I usually use the background I'm "given". Even my posed portraits (very few) I tend to do in natural light.

If you are using a lot of "studio" backgrounds, yes it could get expensive.
 03/24/2004 08:58:00 PM · #12
so youre sure it works this way?
 03/24/2004 09:13:54 PM · #13
//www.gregssandbox.com/bs/bs.htm

This site explains how chroma key aka "bluescreen" works.
03/24/2004 09:24:43 PM · #14
to make a long story short.... its not easy, and it wont work well with my white background?
 03/24/2004 09:31:50 PM · #15
Originally posted by hsteg:
to make a long story short.... its not easy, and it wont work well with my white background?


It is not easy, and it works far better with blue screen than with white background but a black or white background can often be made to work acceptably. Probably alot easier to make a white or black background work with simple products than with a portrait.
 03/24/2004 10:26:04 PM · #16
With chroma key process that is used in TV they normally use blue or green. That being said, I remember watching the news one night and seeing the weather map, not only behind the forecaster, but also in parts of his sweater. He was wearing something that matched the chroma backdrop.

Morgan would probably be a good person to talk to about chroma key.
 03/24/2004 10:53:43 PM · #17
The "key" to chroma-key is to use a color for the background which is unlike any colors in your subject. That's why news anchors never wear blue blouses ...
 03/25/2004 07:55:47 AM · #18
I don't think this is as easy as it seems.

Give it a try for yourself. Take an image with a simple background, and then in Photoshop, go to "Filter > Extract..." and try to "extract" your image from the background. (A quick tutorial that goes over the general idea is available here). The Extract tool allows you to preview your extraction on any solid color, which gives you a feel for how well the extraction went. The key is how sharp can you make the edges. Unless you are proficient at getting a sharp-edged, well-defined extraction, placing a soft, feather-edged portrait on one of these "digital backdrops" will look fake.

It may not be too hard to do with some portraits (preserving wispy hair detail can be a nightmare), but a full-length shot also requires some fancy perspective control of the fake backdrop to get it to look realistic because it has to transition from vertical to horizontal.
 03/25/2004 08:04:32 AM · #19
As Eddy says, there are some situations where it may work well, but others that it is a nightmare. I just did a restoration on someone's wedding photos where the "photographer" photo'd the wedding party on a blue background, and then dropped them onto a background. The veil, the hair of the wispy-do of the bride's maid, and areas around their heads (due to feathering the cut out) were all blue! I had to do alot of salvaging for her. The photog they had hired told them "that was the 'best' they could do!" ACK! This is a prominent studio in my town that has been there for years! Looks like they tried their hand at "going digital" and failed miserably. (side note: this is another reason some people think digital is bad quality compared to film... cuz they do it wrong!). Don't get caught in a trap like this.
 03/25/2004 08:07:10 AM · #20
I purchased a chroma key green background a few months ago, along with a CD containing various background images. The idea with the chroma green or blue is to get a background that contains a color that is very unlikely to be among the colors in the subject. Then, using Photoshop magic, select and eliminate that background, and replace it, via layers, with one from the CD. I don't have anything to show yet (but should in a week or so), but what I've learned from my limited experimenting thus far is that you need to make absolutely certain of two things:

1. Have as much distance between the subject and the background as possible. This ensures that none of the background color will spill onto the subject, making it extremely difficult to subsequently eliminate.

2. The background must be wrinkle free and as evenly lit as possible, thus making for as little variation in tone as possible.
03/25/2004 08:23:02 AM · #21
Referring to the original message . I think all you will get is the 75 backgrounds on a CD, that is exactly what is offered, no more. Whether that is worth 20 USD to you is up to you, but don't expect a magical program to replace the backgrounds in your pictures.

In order to make it usable you will have to shoot a picture that has an even colored background, which then can be easily selected in your editing package and replaced with the background from the CD.

An example :
1) Put up a black velvet background and make sure your subject is well lit and avoid light on the background. Then expose the picture for the subject. This will give you sufficient stops difference between your subject and background, so your background comes out as a solid black in your image. (alternative is a white background with lots of light separately on the background to make sure it is overexposed, or any color but then very evenly lit to facility easy selection).
2) select your background, either manual selection using lasso tool, or automated selection, using the magic wand. Check the selection made and ensure only background is selected, no parts of the subject itself. Subtract any unwanted parts from the selection. If you use it for portraits, the hair of the person or any semi-transparent clothing (brides veil) will cause the most trouble or even make it impossible.
3) inverse the selection so anything but the background is selected. Apply a slight feather to the selection to avoid harsh edges.
4) copy and paste the subject into any other image you have, for example a nice blue sky, a forest, whatever.

This will show you how easy or difficult it is. If you buy the CD you can choose backgrounds from the CD in step 4, instead of any other image. I would not expect more.

Willem

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