infrared photography
 

I asked some members here some questions I had recently over some shots I took and they suggested to post it on here.

About a few months ago, i posted an IR pic on the daily showcase and Mananetwork asked me why there was a gradient on one of the photos, like this one?
http://farm3.static.flickr.com/2479/...192b45f727.jpg

I went out the other day and since it was sunny, decided to do some IR shots. That darker shade seems to occur only during portrait shots (sometimes), and not landscape shots.

http://i950.photobucket.com/albums/a...kytron/gp3.jpg

http://i950.photobucket.com/albums/a...kytron/gp2.jpg

http://i950.photobucket.com/albums/a...onmemorial.jpg

But then again, sometimes it doesn't occur on portait too.

http://i950.photobucket.com/albums/a...kytron/gp1.jpg

Anyone have answers or ideas why this occurs? I'm somewhat clueless and the only hypothesis I have is that it depends on where the light source is and time of day. I doubt it's the camera (5d2), the lens (first pic posted was with a 24-105, everything else 24-70) or the filter (B+W)...:confused::confused:

Oh, shit! I totally forgot to answer you! Sorry... :(

This is most likely caused by the inside of the mirrorbox in the camera. Somehow, under the right conditions, it looks as if some light or infrared light is bouncing off the top of the mirrorbox and causes the exposure discrepancy. It very well may be that the mirror isn't closing all the way in some cases, which is causing a 'lip' inside, leading to a shadow going across the top of the sensor. Maybe there's something loose that is also causing it? Remember, the image is inverted on the sensor, so anything affecting the top of the sensor will manifest itself on the bottom of the image on screen.

Does this happen only with IR shots, or with long exposures?

just curious, im guess u modified the camera sensor to take out the IR filter?

No, he's using a B+W 093 IR filter.

no worries senna!
thanks senna, the light bouncing off the mirrorbox is what i was thinking since there's no loose part around that area and it only happens during IR photos, never on long exposures.

rx_renesis: yeah senna's right, i'm using a B+W filter

No problemo.

Are you a CPS member? Canon will send you a replacement body within 24 hours and you can use that body while they look at your 5DmkII.

...or you can try mine. I can also bring a 5DmkII body from the rental department to see if the problem is inherent to the 5DmkII.

Sadly no i don't qualify as CPS :(
Sure that would be great! When can i bring in the 5d2?

I just thought of something else too. Is it also because when I calibrate the white balance to custom by using a shot of sky or grass with the IR Filter on, that it messes with the resulting captures? It shouldn't, right?

Have you experienced this before Senna?

for reference, here's a long exposure shot, portrait and cropped, showing that the gradient is only observed during IR photos.
http://i950.photobucket.com/albums/a...n/IMG_6497.jpg

I would have to meet you outside of work...somewhere with lots of IR reflecting foliage.

No clue, but it shouldn't affect anything.

Nope, but then again, I only have a Hoya R72. I've never tried a B+W 093.

sweet! I'll get in touch with you once the sun starts coming back out and we can review this IR fiasco. It's not really bothering me as to if my camera or something is loose. It's just bugging me because I can't figure out why it only happens when the shot is portrait.

Yeah I realized that I should have ordered the B+W 092 instead of the 093! the 092 apparently is the equivalent of the Hoya R72. Something about the 093 having a different wavelength for IR

how much do those IR filters costs? and where can i can get one for 67mm??

*look over at senna's direction.

it depends on what kind you get, and filter size.
67mm shouldn't be too expensive. the b+w 093 in 77mm is like 250 or 300 last time i checked. i know the hoya r72 77mm IR costs about 300-350?

b+w has two kinds, 093 and 092. the 092 is the same as the hoya R72 in terms of Ir wavelength. for a 67mm, id wager the price would be something like 150ish? MAYBE? Senna?

there are cheaper IR filters out there like kenko and marumi, but i don't have first hand experience on those so i can't vouch for them. If you have a cokin filter system (or lee, or singh-ray) i know cokin makes them too at a fraction of the cost, but you would need some sort of modular hood to block all light from coming in from the side.

some food for thought! I just read this in my latest "Popular Photography Magazine"

Happy Birthday IR Photography! Back then, they would have never had dreamed of what IR photography has become now, and how it helps society. e.g. weather satellites