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Completely white background, how to?

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  #1  
Old 03-23-2009, 06:31 PM
Bro Photo Bro Photo is offline
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Completely white background, how to?

Hai gais! Lately, I've been doing a lot of shoots requiring a completely white backgrounds...I've been doing fairly well with consistent lighting but 2 hotshoe flashes aren't providing enough power to overexpose the white vinyl backdrops that I use.

The way that I blow out my white backgrounds is dodging the highlights @ 10-35% opacity with the "preserve tone" unchecked. But when I open up levels and drag my midtones to the right, it still shows detail in the highlights...
That and sometimes the background can have a color tinge to it and not be completely white. How do I make my backgrounds completely white without using the eraser tool or white paint brush?
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  #2  
Old 03-23-2009, 09:59 PM
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Re: Completely white background, how to?

Two external flashes, at full shot through an umbrella, softbox, or even bounced of large white v-flats are more than sufficient to blowout a background. It's all comparative to your mainlight. I don't know the exact ratio, 5:1 6:1? I have no idea, but raise your aperture drop your key lights, and it'll blow the background out.

When you say white vinyl background.. is the background material vinyl, like that shiny stuff.. because if it is, your subject will have pretty darn far away from the background so that the light isn't reflected off onto the subject's shoulder.

Once you've shot it right, simply use a raw converter to find white balance so you don't have any color shifts on the white, and it's probably a good idea to check for chromatic aberration. In photoshop you can manually find white balance by checking with numbers (if you don't know, you can search it).

Sometimes you mess up, so photoshop is your friend. Create a levels adjustment layer, slide your shadows slider nearly a third of the histogram to the right. Make sure you have a duplicate of the original image and use your dodging tool, set to highlights (if its selected at shadows or midtones, this may be why your highlights aren't being totally blown out), opacity ususally 15 - 10 %, and just over and over trace around your subject. Try to be careful at this point, but if your brush hits the subject then it usually isn't that big of a deal. When done, make sure you delete your levels adjustment layer. Good luck.
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Old 03-23-2009, 10:59 PM
Bro Photo Bro Photo is offline
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Re: Completely white background, how to?

Quote:
Originally Posted by namphoto View Post
Two external flashes, at full shot through an umbrella, softbox, or even bounced of large white v-flats are more than sufficient to blowout a background. It's all comparative to your mainlight. I don't know the exact ratio, 5:1 6:1? I have no idea, but raise your aperture drop your key lights, and it'll blow the background out.

When you say white vinyl background.. is the background material vinyl, like that shiny stuff.. because if it is, your subject will have pretty darn far away from the background so that the light isn't reflected off onto the subject's shoulder.

Once you've shot it right, simply use a raw converter to find white balance so you don't have any color shifts on the white, and it's probably a good idea to check for chromatic aberration. In photoshop you can manually find white balance by checking with numbers (if you don't know, you can search it).

Sometimes you mess up, so photoshop is your friend. Create a levels adjustment layer, slide your shadows slider nearly a third of the histogram to the right. Make sure you have a duplicate of the original image and use your dodging tool, set to highlights (if its selected at shadows or midtones, this may be why your highlights aren't being totally blown out), opacity ususally 15 - 10 %, and just over and over trace around your subject. Try to be careful at this point, but if your brush hits the subject then it usually isn't that big of a deal. When done, make sure you delete your levels adjustment layer. Good luck.
Thanks for the reply, I got my wording wrong. Atm, I'm lighting the background with 1 flash and the subject with the other flash thru an umbrella. I suppose I could increase my aperture but I'm usually shooting around f/5.6 and any wider, I'd risk having uneven focused body shots. :s then again I could increase ISO...the vinyl is porous and doesn't reflect much light, so spill isn't really a concern.

I shot with a custom WB but it wasn't with 18% gray. I'll do a search about the numbers.

The dodging way you described is exactly what I do but with heavier opacity and with levels adjustment but eliminating midtones to expose the data in the highlights. Yet still there's some artifacting in the shadowy areas that I dodged, I usually notice this when I tilt my screen. It's like spotting dust in my viewfinder

I don't have much problems with CA, (thanks to L lens ) but I could see how that would add problems when dodging out the BG.


Thanks for reply!

I read somewhere you can pinpoint the beginning of the highlights and clip it via curves but I can't seem to find it again... Shoot!
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Old 03-24-2009, 10:16 AM
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Algarve Images Algarve Images is offline
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Smile Re: Completely white background, how to?

As Namphoto has already mentioned the ratio is important and an ideal high key setting would be 4 lights, for example if the subject reading is F8 then the two backlights burning the BG should be F11..
There is a diagram here at:

http://jerrycentral.com/2008/07/09/h...hting-diagram/

Another method, easier if you have a sunny window to place the subject in front of it make sure it has net curains or even better a white silk blind to diffuse the light.
Use fill flash, bump up the ISO and your bg should be burned out.
Here's an example taken in a living room against a bright window with only fill flash...
1/60 @ F4.5
ISO 1600
I underexposed the original so you can see the window, the covering is a net curtain and it worked...
Regards,
Gary...
Attached Images
File Type: jpg sofie_exposure_down.jpg (93.7 KB, 92 views)
File Type: jpg sofie_final.jpg (95.6 KB, 100 views)
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  #5  
Old 03-24-2009, 11:19 AM
Bro Photo Bro Photo is offline
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Re: Completely white background, how to?

Oh! Thanks for the link Algarve Images. If I'm not mistaken the diagram looks like there's only 3 light sources and a reflector. I'll be ordering some Alienbee's this week so lighting will be a lot more easier to manage.
Good example picture too! But I don't think commercial photography would benefit from the light bleed :/ or 1600 ISO haha! Actually, that looks pretty clean.

But since this thread is in the post production section, does anyone know any other alternatives or more efficient ways to correct imbalanced BG lighting?
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Old 03-24-2009, 02:17 PM
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Flora Flora is offline
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Re: Completely white background, how to?

For the colour tinge, you could try with a Hue/Saturation Adjustment Layer:
  • pump up saturation to 100% to identify the colour cast/casts
  • Go to the 'guilty' colour/s and decrease the saturation completely and increase luminosity to 100%
If necessary add a Selective Color Adjustment Layer go to the Whites and decrease the black completely.

Of course, it would be easier if you could post the problem part of your image...
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Old 03-24-2009, 02:24 PM
Bro Photo Bro Photo is offline
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Re: Completely white background, how to?

Quote:
Originally Posted by Flora View Post
For the colour tinge, you could try with a Hue/Saturation Adjustment Layer:
  • pump up saturation to 100% to identify the colour cast/casts
  • Go to the 'guilty' colour/s and decrease the saturation completely and increase luminosity to 100%
If necessary add a Selective Color Adjustment Layer go to the Whites and decrease the black completely.

Of course, it would be easier if you could post the problem part of your image...
Thanks for the info! The pictures are on hold by the company I work for but I think I can swing an upload since I took them.
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Old 03-24-2009, 02:34 PM
Bro Photo Bro Photo is offline
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Re: Completely white background, how to?

Here's an unedited, resized and compressed image I took a few days ago for a website.
When dodging out the highlights and edging into the underexposed areas there's some data left when I adjust my levels. Sometimes when I create marques and hit delete which leaves behind 255/255/255 RGB white, my background is subtly noticeable alongside the white deleted areas. It's not that bad but I'm really anal about pp'ing simple photos like this one.

You can see (well I can at least @_@) a yellowish tinge artifacting around the left girl if you tilt your screen slightly. Haha, I feel pretty goofy about such little details you can barely see.
Attached Images
File Type: jpg IMG_0352smalledit.jpg (86.4 KB, 61 views)
File Type: jpg IMG_0352webhelp.jpg (99.6 KB, 76 views)

Last edited by Bro Photo; 03-24-2009 at 02:41 PM.
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  #9  
Old 03-24-2009, 05:30 PM
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Algarve Images Algarve Images is offline
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Smile Re: Completely white background, how to?

Quote:
Originally Posted by Bro Photo View Post
Oh! Thanks for the link Algarve Images. If I'm not mistaken the diagram looks like there's only 3 light sources and a reflector. I'll be ordering some Alienbee's this week so lighting will be a lot more easier to manage.
Good example picture too! But I don't think commercial photography would benefit from the light bleed :/ or 1600 ISO haha! Actually, that looks pretty clean.

But since this thread is in the post production section, does anyone know any other alternatives or more efficient ways to correct imbalanced BG lighting?
Yep,
looks like 3 lights and thats good for me too as i've ordered 3 elinchrom's from UK.
The D3 is clean up to 1600 and usable at 3,200/6400 for smaller prints, at 800 ISO there is no visible diference from base ISO of 200
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Old 03-24-2009, 05:36 PM
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Re: Completely white background, how to?

Hi again,

using the Hue/Saturation at 100% saturation on your original you can see the different tinges in your background: yellow, red, magenta etc. and there are also a couple of patches of grey. (Attachment 1)

So, even before seeing your corrected version, I also opted for a selection and simply used a Levels Adjustment layer on the selected background.
(Attachment 2) from left: original, white background, adjusted luminosity particularly on the girls faces + lightly increased saturation.

After seeing your correction I used Hue/Saturation at 100% saturation on it and saw what you meant about the very light tinge specially around head and feet of the girl on my left. (Attachment 3)

Probably, the selection you made wasn't very accurate that's why those spots had retained a subtle colour cast. Reselected the background, I used a Selective Color Adjustment Layer (Attachment 4) and the tinge disappeared.
Attached Images
File Type: jpg 2009-Mar-0038.jpg (170.5 KB, 27 views)
File Type: jpg F_IMG_0352smalledit.jpg (199.2 KB, 28 views)
File Type: jpg 2009-Mar-0039.jpg (199.8 KB, 29 views)
File Type: jpg 2009-Mar-0040.jpg (148.1 KB, 29 views)
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