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08-23-2014, 10:14 PM   #1
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Best infrared filter for Kx

Hi guys,
I'm still fairly new to photography (but learning!) and have decided to buy new glass and filters rather than upgrade from my Kx straight away.

I have seen some pretty awesome IR shots, but I know a lot were taken with converted cameras. I understand the focusing issues with filters as well as difficulties setting the white balance. My question is would an IR filter be a worthwhile investment for the Kx to avoid converting it, or would the pictures just not turn out well enough to justify? If it is worth it, is the Hoya R72 still the filter of choice? I saw several on ebay of different wavelengths for cheap, but figured they wouldn't be worth the gamble.

Thanks guys! If this is anywhere else in the forum, I apologize, as I couldn't find it.

08-24-2014, 12:22 AM   #2
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R72 will be ur safest choise. But expect only B&W to be usable cos only pink color in pics.
08-24-2014, 04:22 AM   #3
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The main problem with using a filter on an unconverted camera IMO is the long exposure time. With the filter in front of the lens and the other in front of the sensor there is pretty little light coming through.

I got a 49mm Hoy R72, which I usually put on one of my wider angle manual lenses, using live view manual focusing isn't much of a problem with a wide angle lens. Unless it's a really bright day and/or you don't mind some noise I recommend a tripod. If you don't have one think about getting one anyway, it's useful not only for IR

I don't rely on automatic exposure with the filter, taking a few pictures and checking them on the camera's LCD you can find the right time pretty fast.

I don't think you get anywhere with IR using JPEGs, shoot in RAW and process the result, ufraw and darktable have no problem finding the right white balance automatically which is a good start for further tweaking. Converting to BW is the classical option, but playing with the colour channels can produce some interesting colour results! At least when other people do it, my experiments tended to look rather disappointing.

I once found a rather good tutorial about that, if I find it again, I'll post a link, Anyway, getting the Hoya R72 or maybe another filter if someone here can recommend it is not a waste of money, you can have some fun and produce some interesting pictures with a little work.

Edit: Did not find the tutorial I remembered, but there are quite a lot out there, it looks like you can find a step by step description for processing IR images in every software available. I'd just get the filter and start playing around. Also I think I'll dust up mine and take a few shots myself, haven't done any IR photography in a while

I also remembered this thread about which Pentax lenses are suitable for IR:

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/66895-ir-in...ax-lenses.html

Last edited by mano; 08-24-2014 at 04:59 AM.
08-24-2014, 05:54 AM   #4
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QuoteOriginally posted by mano Quote
getting the Hoya R72 or maybe another filter if someone here can recommend it is not a waste of money
it most certainly isn't. It works well on digital, in particular the K5IIs which doesn't have an Anti-aliasing filter in the optical path*. With film I would even use the substantially stronger RM90 Filter. But Current CMOS sensors aren't as sensitive to IR, in fact they are deliberately made to be insensitive to it as possible. CCDs were better for IR photography because of their deeper electron wells, which worked better at capturing longer wavelengths with reduced crosstalk between pixels that kills contrast with current CMOS sensors (which have shallower electron wells).


Pentax K5IIs - Pentax SMC 50mm f/1.2 with Hoya R72 Filter.


*
from what I have seen the AA filter does mess with image quality in the IR spectrum.


Last edited by Digitalis; 08-24-2014 at 06:05 AM.
08-24-2014, 08:15 AM   #5
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QuoteOriginally posted by Joojoo2010 Quote
R72 will be ur safest choise. But expect only B&W to be usable cos only pink color in pics.
Yes, of course. I am aware than any color will need to be from flipping the red and blue channels then applying some false color if desired.

QuoteOriginally posted by mano Quote
The main problem with using a filter on an unconverted camera IMO is the long exposure time. With the filter in front of the lens and the other in front of the sensor there is pretty little light coming through.

I got a 49mm Hoy R72, which I usually put on one of my wider angle manual lenses...

I don't rely on automatic exposure with the filter, taking a few pictures and checking them on the camera's LCD you can find the right time pretty fast.

I don't think you get anywhere with IR using JPEGs, shoot in RAW and process the result, ufraw and darktable have no problem finding the right white balance automatically which is a good start for further tweaking. Converting to BW is the classical option, but playing with the colour channels can produce some interesting colour results! At least when other people do it, my experiments tended to look rather disappointing.

I am probably going to get the 78mm and use step ups to avoid multiple filters.

And long exposure is fine, I like motion blur in some cases. Manual exposure isn't a problem, I always shoot it, because I am not normally satisfied with shooting auto mode. I use the green button for auto settings, then tweak as desired. And after I made the switch to RAW+, I'll never shoot Jpeg only again. Haha what a difference.

QuoteOriginally posted by Digitalis Quote
it most certainly isn't. It works well on digital, in particular the K5IIs which doesn't have an Anti-aliasing filter in the optical path*. With film I would even use the substantially stronger RM90 Filter. But Current CMOS sensors aren't as sensitive to IR, in fact they are deliberately made to be insensitive to it as possible. CCDs were better for IR photography because of their deeper electron wells, which worked better at capturing longer wavelengths with reduced crosstalk between pixels that kills contrast with current CMOS sensors (which have shallower electron wells).


Pentax K5IIs - Pentax SMC 50mm f/1.2 with Hoya R72 Filter.


*
from what I have seen the AA filter does mess with image quality in the IR spectrum.
Very nice image! I like that. My plan is to upgrade to the K5iis or K3 in the future (college student=no money, plans for grad school=save whatever money I have).
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