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Old January 22nd, 2004, 01:56 AM   #1
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Help needed in filming a white object against an average background

I am using a CANON XL1 with standard 16X zoom lens and 1.6X teleconvertor to film birds at our local wildlife reserve. If the feathers of the birds are anything but WHITE, the XL1 captures it very nicely. The problem starts when birds like STOCKS and CRANES are being filmed. These bird feathers are almost pure white.

The CANON XL1 exposure meter meters the background and gives an average reading which is perfect for the background. However, the white feathers of the birds are rendered totally over-exposed. (The "zebra" pattern appeared on the birds while I was filming them).

The birds are relatively small compared with the background. If I zoomed right in on the birds themselves, the problem essentially disappears - since the meter is now only reading the light values off the birds (feathers).

If I lower the exposure value on the camera to -1 or even -2 stops, just to get the details in the feathers, the background gets under-exposed.

Any workaround / techniques to help in this situation? The distance from the camera to the birds varies - 100m to 300m. I can't use fill-in light nor can I get closer to the birds - against the park regulations.

Thanks,
TS
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Old January 22nd, 2004, 05:26 AM   #2
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That's a tough shoot. Keep in mind that the light meter only METERS
light. It doesn't change any setting for example. Ofcourse if you
shoot in partial or full automatic mode then the camera will base
its decisions on the meter. Best to shoot full manual which I'm
guessing you are already doing.

Basically I don't see a solution to your problem. The contrast is
just too great for the camera to handle. Are you using a PAL
or NTSC camera? If you are using NTSC then the following remark
is only valid if you are not going to broadcast the footage. For
PAL it doesn't matter.

Go into the menu down to custom presets. Change the setup
slider from middle position to all the way to the left. Take note
of which preset you altered (there are 3) and exit the menu's
after your done. Don't forget to ACTIVATE your custom preset
by opening the little red "door". Hit the custom preset SELECT
key until your preset number comes along. It will be flashing
in your viewfinder now. Then hit the custom preset on/off switch
and it should stay lit in your viewfinder. You have now activated
it. This should give you a bit more exposure.

If you can't use this since you are doing NTSC broadcast or it
isn't much help, then you are basically out of luck I think. I would
definitely shoot the background underexposed since it is all
about the birds. I can't imagine the background being *that*
underexposed.

It might be something you can fix in post by using an exposure
curve to bring up the lower end of the curve a stop or two.
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Old January 22nd, 2004, 08:41 AM   #3
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Thanks for the info - I am using PAL. Looks like I have to under-expose the background, then go into POST to bring it up again then. I am wondering how those nice NatGeo's of birds are being handled? I am sure someone will definitely hit the dynamic range limits of his/her movie camera.

I will try it out this weekend and see if the under-exposed background is acceptable.

Thanks,
TS
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Old January 22nd, 2004, 09:18 AM   #4
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The better solution is to tape these birds with a darker background. Is that possible?
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Old January 22nd, 2004, 09:42 AM   #5
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You'll have to go with underexposed background. I've noticed in my limited experience with the XL1 that it seems to have less latitude than the Sony equivalent. Just go for proper bird exposure. The long shots are never going to look as good as the closer shots. With that long lens and extender, a darker, soft background should pop the foreground birds nicely. You might want to try one of the low contrast filters.
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Old January 22nd, 2004, 11:49 AM   #6
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TS,

how are NatGeo films done? By using a wider dynamic range medium than DV - like DigiBeta (10 bit) or film.

I've said it before and I'll say it again - I look forward to the day there is a cheap 10 bit medium as readily available as DV, even if it's only standard def. I'll buy that sooner than 8 bit hi def...

Regards,

Julian
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Old January 22nd, 2004, 04:05 PM   #7
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Since you are using PAL lower your setup level to the minium!
This will give you extra contrast, I'm not sure if it is a full stop,
but everything helps.
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Old January 22nd, 2004, 07:57 PM   #8
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Thank you, very much for all those replies. Now I see the limitations of DV. Not much choice here :-(. I will try to lower the exposure value (read - expose for the Storks and Cranes - and ignore the background) - and see if my results are acceptable. Otherwise, it shall be some creative post work to bring up the background without pushing the birds into the over-exp region.

TS
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Old January 22nd, 2004, 09:13 PM   #9
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What time of day are you filming?
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Old January 22nd, 2004, 10:00 PM   #10
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Could a polarizing filter help here?
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Old January 22nd, 2004, 10:15 PM   #11
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No, a polarizer will saturate colors, but will not help with the dynamic range of the scene. If it were just a scenic, a graduated ND filter would allow the range to be brought closer. But a small white subject would not lend itself to the use of a grad.

Things that would help include getting closer to your subject, use softer light (cloudy day), getting the dynamic range of the scene smaller, change the time of day your shooting, and front light your subject rather than side or back light.

A basic exposure for white subjects on a sunny day would be F16 @ 1/500 or 1/1000 of a second shutter speed. This may need to be reduced depending on your gain and the use of the ND filter. Can you post any examples?
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Old January 23rd, 2004, 03:24 AM   #12
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Thanks for the info.

Time of day - early morning (7am - 10am). The best time of the day for bird videography. After 10am, most of them would have "retired". It didn't help that the sun was very bright that day. After 10am, it starts to get cloudy, but most of the birds were gone.

Jeff, you asked me to upload some examples. I can't see anyway to upload a JPEG file (still clip frame extract from the original DV source) into this website. Please show me the directions for doing so.

Thanks,
TS
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Old January 23rd, 2004, 04:07 AM   #13
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TingSern Wong

I think you might want to have a look at the Ultra Contrast Filters from Tiffen.

http://www.tiffen.com/contrast_filters.htm
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Old January 23rd, 2004, 04:51 AM   #14
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TS: There is no way to post pictures directly on these forums you can only link to pictures. This helps keep things neat and speedy for all users, but it can be a hassle if you don't have a site you can upload the pictures to.

If you want you can send me a couple pictures and I can host them on my site for a few weeks.

Cheers,
Brian
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Old January 23rd, 2004, 08:36 AM   #15
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Set proper exposure on the birds, not the background.
Underexposed subjects or backgrounds can be corrected in post. Overexposed subjects cannot.

Try not to leave your aperture in Auto mode. It settles for an average aperture and will wash out all highlights if the background is mostly green foliage.

I generally start out with Auto-iris, aim to frame, switch to manual aperture and close 1 or 2 stops.

A polarizer filter will remove flares and bring out vivid colors, but it has to be a high-quality glass if you zoom in to 10x or 20x. On a sunny day, the polarizer will give you darker blue skies and brighter colored birds.

Have fun!
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