526Views7Replies

Author Options:

Blue led photography... Answered

I just took some new pictures for my BraceLED 2.0 I'ble. And look at the picture of the bracelet with the blue LED's! The reflection of the blue light on the white surface (=paper sheet) is highly overexposed!

How does this happen? Is the cmos sensor in my Nikon D300s over-sensitive to this color of blue? A picture of a red-led-bracelet under (almost) the same conditions has no such effect.

Picture red BraceLED: iso800, 35 mm prime, f/4, 1/20
Picture blue BraceLED: iso800, 35 mm prime lens, 1/15


Discussions

0
None
lemonie

8 years ago

It's balance :you're throwing bright light onto a reflective-surface so you are getting bright-spots.

Software can blend different exposures, but I couldn't name any right now.

L

0
None
ynzelemonie

Reply 8 years ago

Do you mean HDR (High Dynamic Range) pictures? Never done that, but I guess it can be useful. Thnx!

0
None
lemonieynze

Reply 8 years ago

I think that is it yes.

L

0
None
caitlinsdad

8 years ago

Digital camera sensors can be more sensitive to parts of the light spectrum we don't see and will show up on the image. Being a "clear" LED may leave the light unfiltered. I know you can "see" the infrared coming off of a TV remote with a videocamera, probably a digital camera too.

0
None
NachoMahmacaitlinsdad

Reply 8 years ago

. Plus the light sensors are often center-weighted. Since the center of the picture is dark, the iris is opened more (or whatever they do with digital cameras nowadays) and the bright places end up overexposed.

0
None
ynzeNachoMahma

Reply 8 years ago

Thnx for the comments! The camera was set manually. Because of the strong contrast in the picture, I used a 55% grey card to measure the "light-strength" with the camera, using the "A"-setting (aperture fixed, the camera seeks an appropriate shutter-time). I set those values manually, and took the picture above.

changing the whitebalance K-value in the raw-file doesn't make the light spotes disappear...

I'll try to find the specs of the leds I used. Maybe they are emitting infrared or UV like crazy. After reading your comments, my guess is that the spots are UV-colored, because the red led's don't show the spots.

0
None
killerjackalope

8 years ago

White balance and the method it uses to meter the exposure are likely the cause of this.

Try using manual settings.