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Schurz Park View - Digital Infrared

31 July, 2008 (12:41)

schurz-park-ir-2240 Schurz Park View - Digital Infrared

I did make a bit of a discovery this morning. I realized that I had not tested the 72 filter on the 40D with proper white balance off of grass. Voila. This was shot at ASA 400 / F2.8 and only 1 second. The results are also more pleasing to me since I’m not looking for super-infrared, if you know what I mean. Not hand-holdable but you don’t have to worry so much about all the trees swaying etc.

As Ed mentioned a while back - I need to try this with the deep red filter and the green grass as custom white balance. It’s still not an exact science sort of thing. What do you set the white balance at when you are taking the custom white balance shot - AWB, Sun, some particular temp.

And it is definitely different with different digital cameras. When I tested the R72 filter with the A640 powershot there was no difference in exposure between the 72 and the 87.

The other thing I realized was that the first time I tried the 72 on the 40D I didn’t set what I’ll call the “green grass” white balance. So that threw everything off.

* * *

The Rebel XT arrived a few minutes ago. Funny how small it feels compared to the 40D. Anyway, I’m waiting for the battery to charge; I’ll do a few tests just to make sure it’s working; and then I’m going to send it off for the infrared conversion at LifePixel. Another interesting note on their site:

“Rebel XTi, XSi & 40D require ultra thin filters and because of this the Deep BW filter for this model will still have a little visible light leackage. In order to attain a pure BW image you will need to set your camera to capture in BW mode.”

* * *

And off it goes.  LifePixel should have it by Weds.



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Comments

Comment from Craig Nisnewitz
Time: July 31, 2008, 4:27 pm

How are you determining the white balance settings?

Comment from Oliver
Time: July 31, 2008, 4:29 pm

Fantastic contrasts!
Do you need to take care about the white balance when shooting IR in RAW?

Comment from Dave Beckerman
Time: July 31, 2008, 5:19 pm

Oliver, Craig, and anyone else that’s interested:

**It is all about the white balance, even when shooting in RAW**. That’s what surprised me as I got into this.

So yes - it is tricky to get it right. Basically you are going to shoot at a nice big spread of grass, WITH the filter of choice on. If you are using an uncoverted camera (as I am right now) this means you don’t see what you’re shooting for this color balance shot. So when you’re taking this shot that will be used for a custom white balance - what do you set your white balance to?

I’m not sure. I’ve been setting it to SUN. But I’m not sure if that’s even right.

Also, you’ve got to pick the right color display settings, before using the shot as the basis for your custom white balance. For example, with the 40D it might be “Neutral.” “Faithful,” doesn’t work well.

Then you do your custom white balance off that grass shot, and from then on you shoot using that custom balance.

The way you know if your custom balance is close is that the LCD images, even though you may have the display set to “neutral” are going to look pretty much b&w; though there may be some areas with red. You are shooting in color.

So after that, if you’ve got the balance right, it’s a pretty straightfoward conversion in Lightroom. I find that several of their presets get pretty close. This was done with the high-contrast pre-set, and then pulling down the exposure a little bit. Nothing else.

Comment from Ed Richards
Time: July 31, 2008, 5:40 pm

White balance should not affect RAW at all. I do not use Lightroom, but I do not think Camera Raw cares about the white balance from the camera, as long as change the default during conversion. One thing you might try is to shoot a gray card and see if you can then use it to set the white balance in Lightroom.

Comment from Dave Beckerman
Time: July 31, 2008, 5:55 pm

Ed. I agree. It shouldn’t matter at all with RAW - but it does. In fact, even at LifePixel they suggest the green grass balance thing - though they don’t specify that it’s needed with RAW.

I began with a gray card. Then with the other side (white). This is what works (grass) but I don’t know why.

Comment from Ed Richards
Time: July 31, 2008, 8:43 pm

Have you tried photoshop and ARC rather the Lightroom?

Comment from Dennis Ward
Time: August 1, 2008, 6:46 am

Try thinking of setting white balance as being similar to tuning a musical instrument - say a guitar. By tuning all the strings slightly higher or lower you are tuning them to different frequencies with a given frequency or note being of a standard pitch that everybody uses. Light is measured by wavelength which is directly related to the frequency. Instead of musical pitch we concern ourselves with visible color when tuning a white balance and so we tune our cameras to standard daylight.

Infrared photography is working at wavelengths outside the range of our perception. Electronic sensors can see it but our eyes can’t. This is a bit like those ultrasonic dog whistles - we can’t hear them but our dogs sure can! Using the musical analogy again tuning white balance for IR is like tuning a guitar to a range we can no longer hear. Like transposing a song into a different key.

So why take white balance off green leaves or grass? Because that is the wavelength we want to appear white in our view of the IR world.

As to white balance and raw…… I’ve set a custom white balance on the Nikon from green grass just as lifepixel suggest. I used to wonder why white balance was necessary if shooting RAW. It is certainly needed for JPEGs. RAW converters do take the camera’s white balance as a starting point in processing. LCD presentation on the camera is tied to white balance too. Dave, that’s why your LCD image looks black and white.

The exposure difference between your A640 and 40D with a given filter is probably due to different spectral sensitivities of the sensors and also the inbuilt filters the manufacturer places over the sensors. I guess it’s possible the exposure meters may also have different sensitivity to IR light. I don’t meter with the camera at all usually. I manually focus the lens trying to compensate for focus shift in IR ( remember lenses are designed for ‘visible’ light not IR or UV ). Aperture is set for a reasonable hyperfocal depth of field and then shutter speed gets tricked around for a good exposure. My D1x has a woeful LCD so the histogram is best used to avoid highlight clipping.

Keep at it Dave! I’ve been looking out for your IR posts the last couple of weeks. Any chance of seeing some ‘color’ IR with the 72 filter?

Comment from Dave Beckerman
Time: August 1, 2008, 7:10 am

“As to white balance and raw…… I’ve set a custom white balance on the Nikon from green grass just as lifepixel suggest. I used to wonder why white balance was necessary if shooting RAW. It is certainly needed for JPEGs. RAW converters do take the camera’s white balance as a starting point in processing. LCD presentation on the camera is tied to white balance too. Dave, that’s why your LCD image looks black and white.”

I think that’s as close to explaining it as my brain can comprehend.

I have tried working with raw images that were shot with white / gray card infrared in ARC, and results are the same… There just isn’t enough blue information to compensate.

Anyway - ever the pragmatist - yes, the white balance off the thing you want to be white or somewhere near white and which is sending out it’s invisible light is how you go.

I’ll post some “color 72 ir” if I get anything interesting.

My Rebel XT (unconverted body) should arrive today. I will test it a bit, and then send it off to LifePixel.

I’m not sure that I need to send my “favorite lens” out since I’m always shooting wide angle and will just stop down to compensate for the IR focal length… on the other hand, it would be interesting to actually be able to shoot wide open or there about with the 30mm…. on the other hand… they do it for the 50mm f1.8 and I have a nice 50mm f1.4 which should be close… but then… :)

Comment from anonymous
Time: August 1, 2008, 5:51 pm

As you’ve noticed, vegetation reflects strongly in the IR. This was actually a problem for manufacturers of military camouflage netting when the first IR video cameras and night vision systems were introduced. The camouflage didn’t look realistic in the IR even though it was green and brown in the visible! This is also why grass is a good choice for setting the white balance if you want to do what essentially amounts to “IR intensity” in B&W. Most photography grade filters are pretty broad. But, you can compensate for that with the custom white balance on something that is very reflective in the IR and less so in the visible. All that is to say shooting grass for white balance is more or less equivalent to adding a cascaded filter that can be applied in software (in your case, the camera’s firmware). Another analogy might be the EQ on your stereo…

Comment from richo
Time: August 3, 2008, 9:09 am

This image I meant. It is just wonderful!
-r-

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