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Thread: Problem With IR Custom White Balance on SD14

  1. #1

    Problem With IR Custom White Balance on SD14

    I'm getting really interested in IR photography. I got my hands on an almost new SD14 body on eBay. I removed the UV/IR filter and placed an IR filter over the lens. The camera refuses to take a successful custom white balance of green grass! I purchased a UV/IR glass filter and placed this over the lens. I got a custom white balance straight away. But due to this my images are coming out very magenta coloured. Is there any way I can get this SD14 to get an IR custom white balance?

    Thank you.

  2. #2
    Moderator Manfred M's Avatar
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    Re: Problem With IR Custom White Balance on SD14

    Without getting into details, this is exactly the outcome one would expect. The chlorophyll in grass and other leaves is transparent to IR and certainly in colour IR film, magenta grass and leaves were the norm. The red detect layer in the Foveon sensor would be sensitive to any IR coming through, now that the IR cutoff filter has been removed. Putting an IR/UV filter back on the camera means that you have sort of reverted back to what it was designed to handle, but the IR cutoff frequencies are not the same as the filter that was over the sensor, and some near IR is getting through. Frankly, I'm not quite sure why you would remove the internal IR / UV filter only to replace it with an external one.

    The fact that a custom white balance is not happening is a combination of you operating the camera outside of the parameters it was designed to operate under. You might be able to get a bit more correction in post-processing, but I certainly wouldn't expect miracles and you will see knock-on effect; if you increase the green component in the grass, any other green in the image will increase as well.

    Nicely said; you have decided to get into IR photography, and you are certainly seeing the results. You might want to consider converting to B&W where all the funky colour effects disappear; you do need a B&W IR filter to do this; I think something like a Wratten 25A was what I used to use (very red colour) with B&W IR film. That will get you white leaves and light gray to white grass, with most other things looking more normal.

    You seem to be finding out the hard way, the laws of physics are driving your results. If you understand the underlying technology, you should be able to tweak the results a bit.
    Last edited by Manfred M; 15th August 2014 at 11:54 AM.

  3. #3

    Re: Problem With IR Custom White Balance on SD14

    Looks like another learning curve ahead.

    I used to do colour printing in my darkroom but inkjet printers did away with that (and the cost of the paper). However I still do monochrome darkroom work. I also make digital negatives to print from. This IR subject is going to take some investigation to get similar results to those I have seen posted on the net.

    I removed the internal filter believing I could do 'straight' IR photographs, which is what was intimated by several threads in articles I read on the 'net', before I purchased the SD14 (wrong assumption) with short exposure times. I find I have to use IR filter over the lens to get a decent image. I replace the internal UV/IR filter with the external one when I want to occasionally revert to 'normal' colour photography. But I purchased this SD14 mainly to do IR.

    Thank you for taking the time to reply to my question.
    Last edited by albatross; 16th August 2014 at 07:23 AM.

  4. #4

    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by GrumpyDiver View Post
    Without getting into details, this is exactly the outcome one would expect. The chlorophyll in grass and other leaves is transparent to IR and certainly in colour IR film, magenta grass and leaves were the norm. The red detect layer in the Foveon sensor would be sensitive to any IR coming through, now that the IR cutoff filter has been removed. Putting an IR/UV filter back on the camera means that you have sort of reverted back to what it was designed to handle, but the IR cutoff frequencies are not the same as the filter that was over the sensor, and some near IR is getting through. Frankly, I'm not quite sure why you would remove the internal IR / UV filter only to replace it with an external one.

    The fact that a custom white balance is not happening is a combination of you operating the camera outside of the parameters it was designed to operate under. You might be able to get a bit more correction in post-processing, but I certainly wouldn't expect miracles and you will see knock-on effect; if you increase the green component in the grass, any other green in the image will increase as well.

    Nicely said; you have decided to get into IR photography, and you are certainly seeing the results. You might want to consider converting to B&W where all the funky colour effects disappear; you do need a B&W IR filter to do this; I think something like a Wratten 25A was what I used to use (very red colour) with B&W IR film. That will get you white leaves and light gray to white grass, with most other things looking more normal.

    You seem to be finding out the hard way, the laws of physics are driving your results. If you understand the underlying technology, you should be able to tweak the results a bit.
    Thanks for the comments. I have finally found a way of getting a CW Balance. I purchased an IR/UV 'blue' filter. I just put it over the lens and get a good white balance each time. I then remove it for my IR photography.

  5. #5

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    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by albatross View Post
    I'm getting really interested in IR photography. I got my hands on an almost new SD14 body on eBay. I removed the UV/IR filter and placed an IR filter over the lens. The camera refuses to take a successful custom white balance of green grass! I purchased a UV/IR glass filter and placed this over the lens. I got a custom white balance straight away. But due to this my images are coming out very magenta coloured. Is there any way I can get this SD14 to get an IR custom white balance?

    Thank you.
    I can help you quite a lot with your problem. I also have the SD14, currently with filter removed, just like yours. I usually use Incandescent WB if I can't capture a good custom WB. Have also used the SD10 and the SD1M for IR.

    The SD14 is pretty poor at capturing a custom WB in full-spectrum work, with or without an IR lens on the lens. It doesn't matter that much because the horrible magenta cast will appear in any case. This is because the converter (SPP, FastStone, dcraw, etc) is trying to produce RGB from seriously unbalanced raw data. For example the SD10 responds to IR approximately in the ratio of 6:2:1 (bottom, middle, top layers - RGB channels). I find Incandescent WB good enough on the SD14 for my purposes.

    So the question should perhaps be "how can I prevent the magenta cast?". I would recommend strongly that you get an app called RawDigger. Amongst other good things like providing true raw histograms it can export TIFF images:

    RGB rendered.
    Raw Composite.
    A single -channel R, G, or B.

    In particular, the 8-bit RGB and the 8-bit composite renderings are less magenta-heavy and easier to turn into an IR masterpiece. The single-channel exports are mono 16-bit, with or without 2.2 gamma.

    This is a RGB export from RawDigger. Just a full-spectrum (no filter on lens) snapshot of the barn with the SD14 and Incandescent WB, no color post-processing at all. No SPP involved either:

    Problem With IR Custom White Balance on SD14

    As you can see, a slight blue cast in neutral areas like the tin roof and the discarded A/C. The green foliage reflects some IR hence the brown coloration. Any technical questions gladly answered.

    You'll probably find my post over on DPI interesting, re: the various renditions possible before post-processing:

    http://www.getdpi.com/forum/other-ca...tml#post655222
    .
    Last edited by xpatUSA; 25th September 2015 at 10:40 PM.

  6. #6

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    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by albatross
    Thanks for the comments. I have finally found a way of getting a CW Balance. I purchased an IR/UV 'blue' filter. I just put it over the lens and get a good white balance each time. I then remove it for my IR photography.
    I read this quote after I had posted above. IMHO, there's something not quite right about getting a custom white balance for an IR shot by effectively reverting the camera to normal, taking a custom white balance, and then reverting back to IR by putting an e.g. Hoya 720nm filter on the lens.

    You see, there is no "white" to balance in wavelengths above, say 730nm. In other words, all IR emission is outside of the CIE horseshoe diagram and contains no colors at all. Therefore, fiddling around the white balance setting in-camera will make little difference to the RGB conversion from the X3F raw data, especially if opened in SPP - it will be that horrible purple color, no matter what we set the WB to.

    I'm open to more discussion on this, since we do have the same cameras set for full-spectrum/IR photography.

  7. #7

    Re: Problem With IR Custom White Balance on SD14

    A real big 'thank you' for your posts. I will give the suggestions a testing this week. I'll have a look at the post you linked to in you first reply. I am getting some much better results than previously. I do have Rawdigger and think it is a fantastic piece of software for IR work.

  8. #8

    Re: Problem With IR Custom White Balance on SD14

    I thought I would post a picture taken using my CWB setup on my SD14 using an UV/IR 'blue filter'. The photo was then taken without any filter on the lens. I quite like the result. I have tried channel swapping with some interesting results. The 'red' channel gives a very nice black and white IR image.[IMG]Problem With IR Custom White Balance on SD14[/IMG].

  9. #9

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    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by albatross View Post
    Problem With IR Custom White Balance on SD14

    I thought I would post a picture taken using my CWB setup on my SD14 using an UV/IR 'blue filter'. The photo was then taken without any filter on the lens. I quite like the result. I have tried channel swapping with some interesting results. The 'red' channel gives a very nice black and white IR image.
    Always nice when the sky stays blue, eh? With the red channel exports, unchecking the 'gamma' box in RawTherapee can sometimes reward one with some serious mid/upper contrast at the expense of shadow detail but, at 16bits, that can be brought up in post. For example, dark and sombre:

    Problem With IR Custom White Balance on SD14

    Pardon the wacky processing, it's always fun to play and this one received an outlandish tone curve !

  10. #10

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    Re: Problem With IR Custom White Balance on SD14

    I'm allways getting confused when talking about filters. As far as I know there're 2 groups of filters: blocking and passing. The filter in the camera before the sensor is a ir blocking filter, and the filter you place before the lens is a passing filter. As far as I believe. I can be wrong.

    George

  11. #11

    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by george013 View Post
    I'm allways getting confused when talking about filters. As far as I know there're 2 groups of filters: blocking and passing. The filter in the camera before the sensor is a ir blocking filter, and the filter you place before the lens is a passing filter. As far as I believe. I can be wrong.

    George
    The filter fitted internally over the sensor (which I have removed) is an IR blocking filter and I think it blocks some UV as well.

    So when I put my external UV/IR blocking filter over the lens it temporarily it returns the filtration back to normal (obviously not a perfect match for the removed filter). If I want to take a non IR photograph. I simply hold that filter in front of the lens.

    Dennis

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    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by albatross View Post
    The filter fitted internally over the sensor (which I have removed) is an IR blocking filter and I think it blocks some UV as well.

    Dennis
    Quite right, and here it is:

    Problem With IR Custom White Balance on SD14

    The graph is 'upside down' because the instrument (not mine) was measuring the blocking characteristic. It does give the cut-off wavelengths and it is an SD14 UV/IR blocking filter, also known as "the dust-cover".

    Non-Sigma owners should know and be jealous of the fact that the "dust-cover" pops out with your thumb-nail and is easily replaced. This certainly beats sending your pride and joy off to some back-street shop to have the "hot mirror" ground off of the sensor ;-)
    Last edited by xpatUSA; 25th September 2015 at 06:48 PM. Reason: slight re-wording

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    Re: Problem With IR Custom White Balance on SD14

    I bought a Hoya R72 IR filter about 10 days ago which was earlier than I planned because the price of the filter was going up fast in Turkey .So, I will have to learn how to shoot and how to process IR images in time . This link has some useful info about IR photography and it might be helpful for some members

    http://www.lifepixel.com/tutorials/i...otoshop-videos

  14. #14

    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by bnnrcn View Post
    I bought a Hoya R72 IR filter about 10 days ago which was earlier than I planned because the price of the filter was going up fast in Turkey .So, I will have to learn how to shoot and how to process IR images in time . This link has some useful info about IR photography and it might be helpful for some members

    http://www.lifepixel.com/tutorials/i...otoshop-videos
    LifePixel are an excellent company to deal with. I needed advice about IR filters. Even though I did not send my other camera to them for modification, they were still very helpful.

    Dennis

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    William W's Avatar
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    Re: Problem With IR Custom White Balance on SD14

    Quote Originally Posted by albatross View Post
    A real big 'thank you' for your posts.
    Ditto.

    Ta Ted. very, VERY helpful.

    Bill

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