[Andrew Faires]

What I know about IR photograph could best be described as 'grossly limited'. When it comes to the Pentax line-up, I understand the K100D is pretty sensitive to IR light, while the K10D isn't very sensitive to it.

This brings me to my questions - and theres three:

1) Is the K100D super as sensitive to IR light as the K100D?

2) Would a used *ist series of camera be as sensitive to IR light as the K100D? (ie, would it be better to buy a used DS2 or a K100D for the sake of doing IR photography?)

3) With my K10D, I can shoot IR, but the colour image displays a verticle banding. Keep in mind, this is the only time I've noticed this and when I convert the image to black & white, the banding is no longer visible. Is this a problem with my sensor and the longer exposures nessessary to make the image (using an IR filter, of course) or is this to be expected? (I can post a sample tomorrow morning if that will help)

Thanks for the advice/help!

[khardur]

Andrew: AFAIK, the K100D Super uses the same sensor, so it should be just as sensitive to IR as the K100D.

2. I don't know this one.

3. Occasionally in my experience, there's a spot up about 1/10th of the way from the bottom of the image (when shooting horizontally) that seems to have some sort of light flooding. It has happened to me on occasion, and when converting to B&W most of the time it "goes away".

is it vertical banding on a horizontal image? If that's the case I'd say it could be underexposure - you really have to push the right edge of the histogram to get a good low grain/low noise exposure. (and yes, it's a very fine line between a good exposure and completely blowing out half the image, and it's especially frustrating when you're doing long exposures)

[carpents]

1) Is the K100D super as sensitive to IR light as the K100D?

Without owning either, my educated guess is 'yes'.

2) Would a used *ist series of camera be as sensitive to IR light as the K100D? (ie, would it be better to buy a used DS2 or a K100D for the sake of doing IR photography?)

Yes, the *ist series is as sensitive as the K100D. Someone here with both showed that they have a similar sensitivity. I assume you are asking if they would be better than the K10D, which they all are.

3) With my K10D, I can shoot IR, but the colour image displays a verticle banding.

You'd have to show a picture. I actually returned my Hoya R72 because a defect in the filter was showing in the images. At first I thought it was flare, but upon close inspection it was actually a flaw in the filter itself. An example, pretty clearly showing the flaw:

[Andrew Faires]

Thanks for the info, Carpents & Dan!

Here's the original, unedited (aside from resizing) shot. The banding is verticle in horizontal framing and it's most noticable in the bottom left corner as blue banding on the reddish colour.

Carpents, I never suspected the filter and based on your example I doubt that's the case. Might be under-exposure based on what Dan's described.

Would it help if I put the contrast to -2 on the camera menu?

[Duplo]

I shoot a fair bit of IR.

1) I have not tied on a K100D or K100D super, but I have seen decent results from the K100D and would asume the same would go for the super.

2) the Ds is rather sensitive to IR, especially in the red channel.
Here is an example:
(Ds - DA40 - 1/s - f8.0 - ISO 100)

THe Ds as the K100D benefits from a higher base sensitivity, as well as a higher sensitivity to IR in general.

3) Well I actually use my R72 filter quite a lot on the K10D, exclusively for B&W though.
and it does have certain advantages, mainly the ability to achieve long shutter speeds at broad daylight.

I have seen two examples of an odd noice pattern in my photos, one was due to flare and the other that I did not cover the viewfinder. The latter is very important to avoid it.

Anyway here are a few examples of my use of it:

K10D - A24 - 30s - f4.0 - ISO 640


K10D - FA77ltd - 30s - f7.1 - ISO 100


K10D - A24 - 30s - f7.1 - ISO 400


A quickly compiled IR gallery of mine can be found HERE

[Andrew Faires]

Beautiful shots and gallery Thomas. I'll have another go with the K10D this weekend. I didn't cover the viewfinder, so that could be part of the problem - hopefully it's as simple as that & some underexposure.

Thanks again for the replies!

[jshurak]

how do you guys calculate exposure settings on those?

[carpents]

The banding is verticle in horizontal framing and it's most noticable in the bottom left corner as blue banding on the reddish colour.

I don't see anything out of the ordinary. If covering the viewfinder doesn't help, try to post a 100% crop of the offending area.

how do you guys calculate exposure settings on those?

The camera can meter for IR. I shoot mine in Av mode with between +1 and +2 Ev exposure compensation, depending on the scene.

[Duplo]

how do you guys calculate exposure settings on those?

I used trial and error at first. along the way you develop a feel for what settings to use for a given scene, at least I have done.

I usually shoot one guestimate, finetune WB and exposure ( usually within 1 stop) and makes my final capture.

Works for me... I ignore the in camera metering when doing IR photography.

[jshurak]

thanks everyone. I'll give both a shot!

[khardur]

exposures: a lot of trial and error, like Duplo said. I generally start out (in manual mode) with the aperture I want, then adjust the shutter speed until the meter reads +2.5. That's where I start my exposures off, and I adjust from there as needed.

(this is referring to the K110D/K100D sensor)

[egarrard]

Duplo, thanks for posting the K10D pics. I don't have to give up IR! A couple of questions though. Do you have noise reduction on? How do you focus with the A lenses?

[Duplo]

Duplo, thanks for posting the K10D pics. I don't have to give up IR! A couple of questions though. Do you have noise reduction on? How do you focus with the A lenses?

No problems.

The steps I use:
compose, focus manually, (if an AF lens switch back to AF), attach IR filter, (if an AF lens switch back to MF), dial in exposure settings, hit the shutter.

I do not have noise reduction on. I prefer doing that in PP.

[LeoTaylor]

At the risk of repeating myself... Actually since the Forum considers IR too short to search for thus there are several IR threads at once.

When shooting IR the red channel is the only useful data. You will get better results (and no blue or green streaks) if you use software that extracts only RED pixels from the Bayer Array. The Blue and Green are adding artifacts. The image will be only 1.5 megapixels, but I rather not have 4.5 megapixels of extra junk to process out of my images.

I use images Plus, I'm sure other programs are capable of extracting Red only from a RAW file.

[Duplo]

At the risk of repeating myself... Actually since the Forum considers IR too short to search for thus there are several IR threads at once.

When shooting IR the red channel is the only useful data. You will get better results (and no blue or green streaks) if you use software that extracts only RED pixels from the Bayer Array. The Blue and Green are adding artifacts. The image will be only 1.5 megapixels, but I rather not have 4.5 megapixels of extra junk to process out of my images.

I use images Plus, I'm sure other programs are capable of extracting Red only from a RAW file.

Well easy now Leo. You come across pretty harsh to me.

I recall two currently running about IR, someone asking for a lighter IR filter than the Hoya R72 IIRC and this thread that I have come across lately.

Well I guess those making colour IR from their digital cameras will have to disagree with you, I have seen a few people doing that and with quite impressive results.

If you are using a stronger filter like the R90 you may be right, but the R72 actually let some green and blue light pass through too, why not use that as part of your Image?

I guess I do not see the point of excluding 3/4 of your imagedata.