IR Filters, really IR?

AshleyC

AshleyC

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Ive got the Cokin P007 infra red filter and just wondering if its really an IR lens or just a very dark red filter.

I ask because if i hold it up to a window or a lightbulb or something bright i can see an image through it. Surely if it was letting only IR wavelengths through i wouldn't be able to see anything?

The other point was that with images taken with it, see below, i would expect the foliage in the tree to be almost white rather than dark. Leaves radiate bucket loads of IR apparently. All i did was took the original image and hit the black and white button. Im assumng all the "coloured in" images you see in flikr are just people colouring in their pics in the same way people colourise old B&W films.

So what gives? Are we being diddled? Are there "real" IR filters out there or am i just missing the point?

Original, right out the camera with filter. You can see the leaves are dark in the original, surely they should be white.


Black and Whited
 
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Someone with more expertise will no doubt be along soon, but I was under the impression that many modern DSLR's have a filter on the sensor that significantly reduces IR light.

This will make IR photographer much harder.

I know folk in the past have had the AA filter removed from their camera specifically for IR photography
 
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yeah they do but you just stick it on a tripod and take longer exposures.

I just found this site which is a great read. Essentially it looks like the cokin sucks as it lets in a band of light beneath the IR range as well which is bound to muck things up. And its probably why i can see things through the filter with my, very much non IR converted, eyeballs :)

http://www.infrared-photography.co.uk/

Might have to invest in the hoya and see if things change.
 
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essexash said:
Might have to invest in the hoya and see if things change.
Click to expand...

I have the old Cokin P007, the Hoya R72 and the B&W 092 and I would assess then in that order although the Hoya and B&W are very close. The three are all around 700nm cutoff and if you want to avoid visible light then the B&W 093 (about 850nm cutoff) might be your best option...at a price.

Bob
 
The false colours you see are often produced by channel swapping in photoshop. You can get some quite interesting results just by playing with the colour balance sliders in a raw converter, or with the white balance controls - you don't just have to convert to b&w.
 
True infrared is either difficult or pretty much impossible with a modern DSLR. It's all on your link.

All modern cameras have quite efficient infrared filtering over the sensor so if that's doing its job properly and has a sharp cut-off at the end of visible red, it doesn't matter what filter you put over the lens, no infrared is going to get through.

What you can do with older cameras like Nikon D70 etc with CCD sensors and relatively weak IR blocking, is fit a filter to cut out as much of the visible spectrum as possible and 'force' a bit of deep red and semi-IR light through the 'gap' at the end of the sensor's IR filtration.

Results tend to be poor, and unpredictable at best. Lenses also have different IR-pass characteristics that can either help or hinder. If you're serious about IR photography, getting an older DSLR converted is the only option - but that works very well and is far easier to use.
 
HoppyUK said:
Results tend to be poor, and unpredictable at best. Lenses also have different IR-pass characteristics that can either help or hinder. If you're serious about IR photography, getting an older DSLR converted is the only option - but that works very well and is far easier to use.
Click to expand...

spot on. Cheap D70 with or without a mod is probably the best way forward - certainly stay with crop as most normal lenses will only give decent centre. Zeiss made IR optimised lenses, but if you have to ask the price you can't afford it.
 
I have kept my D40 so I can do some IR with it. I have used a Hoya IR filter and will try to find an example later!


Heather
 
My son's been quite successful using a a Hoya R72 with his Canon 500D. Shutter speeds in good sunlight are around 30s to a minute, so a tripod is essential, but the results are good.

I use a Leica M8 which doesn't have an IR filter over the sensor, so with an R72 I can get easily hand-holdable shutter speeds :)
 
Planning to get my D70 IR converted when it comes back from long term loan (unless the friend who's borrowed it wants to buy it!). Having fun with real IR thermography at the moment - amazing what you can see lurking in the hedges in the dark! Not been near my desktop 'puter recently so not got any ready to show and CBA to do any right now anyway!
 
As has been said, IR photography using a DSLR is difficult to impossible. I still have and use a Cannon T90 because of this (and because i still like taking slide pics lol).
A good cheap SLR can be found just about anywhere nowdays. If you get one along with a few rolls of Ilford SFX 200, you will end up with true infrared images.
 
The Fuji X100 is also very good for IR - I've used a 720nm filter on it and it gives some nice results at easily hand-holdable speeds.
 
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