Infrared white balance on K3


derek897

Link Posted 26/04/2016 - 11:27
Having trouble setting custom wb with the ir filter on K3, it just keeps saying unable to complete, any ideas as to what im doing wrong. im going to wb settings, custom wb, holding the filter over lens, pointing at the grass and 30 sec later unable to complete ?

Any thoughts welcome.
Derek
I know what i like, If not always why.

WobblyGoblin

Link Posted 26/04/2016 - 16:17
At a guess it is taking too long to calculate because there is not enough light getting in. Alternatively it could be that the light coming through is so far to one end of the spectrum that it logs an error.

Either way, is it not easy to just take the picture in RAW and amend the white balance on the PC? Should be relatively simple to correct the colour balance.
You will only prise my 43Ltd from my cold, dead hands...
Last Edited by WobblyGoblin on 26/04/2016 - 16:18

derek897

Link Posted 26/04/2016 - 16:49
You might be right on the length of time, I'll try shortening it. I was leaving it open for 30 secs. That was giving me a white image,, iso ramped up and lens wide open.
I'll see what happens when I try it.
I can set wb in pp but would like to have it in camera too as the K5 can do this. It's hard to know what you have when it's all red.
Thanks
Cheers Derek.
I know what i like, If not always why.

johnriley

Link Posted 26/04/2016 - 17:19
An IR image is bound to be all red because the IR part of the spectrum is beyond red. If I use an R72 filter on my K-5 I would expect it to be red.

I don't see how a custom WB works in this context, because there is no WB.
Best regards, John

derek897

Link Posted 26/04/2016 - 18:30
How it seems to work, to me anyway (I might be wrong) is like this,
Custom wb set by taking overexposed shot of bright grass, as bright green foliage is white in infrared bw, when you take a shot with the external filter on it recognises that the greens are supposed to be white ish and removes the red colour cast.
I'll post an example of both in a min when I get to the pc.

Derek
I know what i like, If not always why.

derek897

Link Posted 26/04/2016 - 18:59
Hi, here is an example of auto wb on K5 and custom wb on K5. These have just been resized, nothing else.
So as straight out of camera as i can get.

Auto wb

IMGP6796smallpu by dr.shutter, on Flickr

Custom wb on K5


IMGP6798smallpu by dr.shutter, on Flickr


IMGP6790smallpu by dr.shutter, on Flickr

Slight difference.
Derek
I know what i like, If not always why.

johnriley

Link Posted 26/04/2016 - 19:12
As an experiment, fair enough, it's something different.

BW IR is something else of course and normally we would convert that red image into monochrome. I use Channel Mixer, but there are many other ways.
Best regards, John

derek897

Link Posted 26/04/2016 - 19:25
As you can see John there is a huge difference, and what if I don't want to go mono.
The K5 allows me to set custom wb.
To get back to my original question, what am I doing wrong that I can't seem to set it on k3. Or does the k3 not allow this ?
I know what i like, If not always why.

johnriley

Link Posted 26/04/2016 - 20:07
In a generalised way, all I can offer is that different cameras behave very differently in their sensitivity or otherwise to IR light. Also of course different scenes under different lighting have huge variations in the amount of IR light present.

If you want pseudo-colour IR then I'd try Google and YouTube to find some online tutorials.
Best regards, John

derek897

Link Posted 26/04/2016 - 23:37
That's grand John, I understand that camera models and makes respond differently to ir as they all have different ir blockers on the sensor.i originally posed the question in case anyone else had come across this and knew why it was, or a work around or that my method for the K3 was incorrect.
There's no hassle.
Cheers
Derek
I know what i like, If not always why.

davidstorm

Link Posted 27/04/2016 - 21:51
Hi Derek

The custom WB is different but I don't think you'll get satisfactory results in colour with this filter, it will always look unnatural and not in a very pleasant way. I would tend to stick with a BW conversion; I know this isn't what you're aiming for, but to get better results you are probably going to need a converted camera.

Regards
David
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derek897

Link Posted 28/04/2016 - 07:46
davidstorm wrote:
Hi Derek

The custom WB is different but I don't think you'll get satisfactory results in colour with this filter, it will always look unnatural and not in a very pleasant way. I would tend to stick with a BW conversion; I know this isn't what you're aiming for, but to get better results you are probably going to need a converted camera.

Regards
David

Cheers David, to be honest I'm not looking to try and take colour shots with the r72, the question about wb came up because when using a custom wb you can see in camera whether or not you have captured enough ir light to make the greens pop, that kind of white when converted to mono. It's difficult to see or tell if they will when the shot is red. In the last shot above its clear in camera that the grass and foliage have that pop.
If I was trying to shoot colour ir I would need to convert a body to do so and shoot in 590 ir or there abouts .

Cheers
Derek
I know what i like, If not always why.

redbusa99

Link Posted 28/04/2016 - 09:59
you take a shot of your nice green lawn in bright sunlight, without the filter, then use that image to set the WB then attach the filter to take the IR shot. You get blue skies by swapping the blue and red colour channels. there are some good tutorials on youtube on using an R72 filter.
K3 II and the odd lens or 2

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Last Edited by redbusa99 on 28/04/2016 - 10:02

derek897

Link Posted 28/04/2016 - 12:49
redbusa99 wrote:
you take a shot of your nice green lawn in bright sunlight, without the filter, then use that image to set the WB then attach the filter to take the IR shot. You get blue skies by swapping the blue and red colour channels. there are some good tutorials on youtube on using an R72 filter.

Cheers,
as far as i know and from looking it up, the filter needs to be on to get the wb, otherwise still in same boat. You are spot on about the bright green grass though, camera needs to recognize the grass as being white with filter on or it defeats the purpose.
I know what i like, If not always why.

petrochemist

Link Posted 28/04/2016 - 13:57
redbusa99 wrote:
you take a shot of your nice green lawn in bright sunlight, without the filter, then use that image to set the WB then attach the filter to take the IR shot. You get blue skies by swapping the blue and red colour channels. there are some good tutorials on youtube on using an R72 filter.

I've heard of people using converted cameras getting pleasing results doing a CWB without the filter, but with the filter is far more common.
FWIW paper, grey card, PTFE, concrete & the sky have all been used for IR CWB of one sort or another, giving different results but all perfectly legitimate.
If your using an unmodified camera a CWB without the filter will be TOTALLY useless, the visible light seen during CWB would swamp any trace IR signal which is all that will be used for the image.

From the exposure times Derek is getting his K3 is unmodified. Doing a channel swap with a R72 & unmodified camera will give you everything blue, as over 99% of the trace infrared normal cameras can see is recorded in the red channel. Using filters below 720nm on unmodified cameras generally just record the visible portion that the filter transmits with no IR being visible.
Mike
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