DIY IR test

[photoSmart42]

My first IR test. Using the FD 28mm/2.8 lens with 2 layers of developed 120 slide film behind a Hoya Skylight (1B) filter. This is the most successful shot of the 12 I took. Had to make a bunch of adjustments until I got something I kinda liked.

ISO 800, f/8, 20" exposure

Learned a lot!
- I definitely need to add a spacer between the filter bottom and the slide film so it holds it as flat as possible against the lens body. I could see the effects of the warped film
- Probably need a lens hood for this. I seem to have gotten better results by using my palm to shield the side of the lens from the sun
- Started out with 3 layers of film and ISO 100, but eventually got it down to 2 layers and ISO 800 to minimize the exposure duration
- Started out with f/2.8, but wasn't getting sufficient DOF to get the scene in focus, so I eventually moved to f/8

I knew going in that using the DIY slide film method wasn't going to yield the sharpest photos, and the resulting grain could be useful for certain cases. I suppose my next step would be to look into an IR filter (way more expensive than my DIY setup), and eventually getting a dedicated IR body so I can make use of the live view feature and not have to guess at composition/focus, etc.

Overall, not a bad experiment.

-Dragos

 

[Vivek]

What kind of camera did you use for this?

These are the AA/UV/IR cut filter stacks from (left) a Panasonic G1 and (right) an Olympus E-410 in IR (Heliopan RM760 filter over the taking lens, modified E-410). These show the absorptive as well reflective nature of these filters towards IR.

There is 0% chance of any stock m4/3rds camera seeing any infra red light.

 

[photoSmart42]

What kind of camera did you use for this?

There is 0% chance of any stock m4/3rds camera seeing any infra red light.

Hmm... interesting. I used my GH1. My understanding is that the developed 120 slide film I'm using as a makeshift filter only allows IR light to pass, and I'm using 2 stacked layers of it to further shift the absorption wavelength. I didn't think any light in the visible spectrum would pass through that, so the corresponding image has to be IR-ish, right?

I'll do the TV remote test today to see if I can 'see' the IR light with this setup. That should be convincing one way or another I think.

 

[Vivek]

If the images I have shown have not convinced you, nothing will.

No IR.

 

[pellicle]

Hi

taken with the Computar C-Mount f1.3 12mm lens on the G1 and a Hoya R73 IR filter. Processing is using dcraw on the image and extracting R and G layers (discarding B) and then blending them to get a combination of hilight detail from the Green layer and shadow from the Red.

Can't be certain exactly how much of this is visible and how much is IR ... but I'd have thought the R73 cut off bucketloads but not infinite, but it sure has the right look for IR (after some years of using Kodak HIE)

 

[pellicle]

There is 0% chance of any stock m4/3rds camera seeing any infra red light.

or perhaps 0.001% ...

 

[Diane B]

I think that's more of the IR thing for me--the 'look'. Whether its visible IR or not.

 

[Vivek]

Hi



taken with the Computar C-Mount f1.3 12mm lens on the G1 and a Hoya R73 IR filter. Processing is using dcraw on the image and extracting R and G layers (discarding B) and then blending them to get a combination of hilight detail from the Green layer and shadow from the Red.

Can't be certain exactly how much of this is visible and how much is IR ... but I'd have thought the R73 cut off bucketloads but not infinite, but it sure has the right look for IR (after some years of using Kodak HIE)

Assuming that you meant Hoya R72 filter (720nm filter, there is no Hoya R73 filter that I know of), it cuts 50% light at ~720nm.

Bucket loads of visible (red). Given the fact that the m4/3rds sensors see no IR, what is recorded is red. Might as well use a red filter.

B&W film (with poor red sensitivity) combined with Red and Polarizers can fake IR while not recording any IR.

The point is that there is no IR. However, if the objective is to record something different for pictorial value then there are all sorts of ways to do it.

 

[photoSmart42]

If the images I have shown have not convinced you, nothing will.

No IR.

Not at all trying to be argumentative or sarcastic. I'm genuinely confused. Here's what my camera sees using the TV remote test which in theory tests the IR sensitivity of the camera sensor. Screenshots taken off GH1 in HD video recording mode using the 20/1.7 lens (two separate remotes):

What I see is a camera sensor that sure seems to see the IR coming from the TV remote. Is there another explanation for what I'm seeing that reconciles with your testing?

 

[Vivek]

Is there another explanation for what I'm seeing that reconciles with your testing?

Yes. Can you see the LEDs with your eyes when you turn them on (try it in the dark)?

If the answer is yes, then your camera is seeing red from remotes.

An 850nm LED I have has its bulk of its output centered around 850nm (truely infra red and invisible to the human eye) but I can see a weak red when it is on.

I am just trying to be helpful w.r.t. IR.

 

[rgeorge911]

Sure looks like IR to me. Ha ha ha! Hard to argue with empirical data (proof). You don't see a visible red beam coming out of that remote, I trust...

Nice job. Pictures are interesting as well!

 

[photoSmart42]

Yes. Can you see the LEDs with your eyes when you turn them on (try it in the dark)?

If the answer is yes, then your camera is seeing red from remotes.

Went inside my closet with the door closed, stuck my head under my shirt for total darkness, and didn't see the LED with my eyes (for completeness, I can normally see reds, so I'm certain I'm not colorblind to reds). Same LED that appears bright and shiny on my camera screen (the second one that has the LED itself visible from the outside). Could the GH1 have a different IR filter than the G1 you tested?

 

[scho]

The IR cut filter in the camera is certainly not 100% efficient so in most cases there is enough IR getting to the sensor for creating a true IR image with the appropriate IR pass filter over the lens. You cannot generate the Wood effect with a wratten dark red filter. This only occurs with near IR radiation reflecting off green vegetation.

 

[pellicle]

Assuming that you meant Hoya R72 filter (720nm filter, there is no Hoya R73 filter that I know of), it cuts 50% light at ~720nm.

correct, my mistake R72

PS: interestingly my red laser pointer (650nm wavelength) shows nothing visible through it (in my dark room) while a very high brightness LED which is "white" shows a dull red glow penetrating it

it cuts out quite a bit of the red and way more than 50% of visible spectra

 

[photoSmart42]

Could the GH1 have a different IR filter than the G1 you tested?

Quoting myself, but I just ran the TV remote test with my wife's G1, and the IR cut filter is definitely different between the G1 and the GH1, at least for the cameras I own. The remote light is still visible on the G1, so it does still allow some IR to pass, but it's at most 50% of the intensity I observed on the GH1.

That seems to confirm some stuff I found on other forums where people were saying one of the ways in which Pana increased the overall sensitivity of the GH1 was to reduce cut filter.

Meanwhile I'll continue my 'IR' experiments on my GH1 because I do like the Wood effect I get through my makeshift filter, whether it's true IR or not. I'll experiment with a single layer as well to see what it does differently, and I'll fix some of the other issues I mentioned in my original post. For having only spent $7 in materials I'm pretty happy with the results.

 

[Vivek]

Fair enough, Dragos. That is what I said earlier as well.

I have had this discussion with Carl in another thread. So, there is no need to repeat it here.

Consider this: A modified (without the AA/IR/UV cut filter) Olympus E-410 shows +2 eV sensitivity when Hoya R72 filter is for IR.

While the stock camera readings for visible light are 2 eV less!

The difference is like night and day. No more tripods and 20 seconds exposure.

Also, you do not need much post capture manipulations to get to where you want to go (what you mention in the first post).

 

[photoSmart42]

Fair enough, Dragos. That is what I said earlier as well.

It's all good =). Thank you for challenging my understanding of IR photos. It forced me to go back and do some additional testing, and I learned something I didn't know this morning. Yay!

 

[Vivek]

FWIW, I have shot "IR" with the same filter you have used on Velvia 50. It did give images with "Woods effect" with a heavy cyan cast.