Infra red photography

[Littletank]

I have two questions and I apologise in advance if these have already been covered. Firstly, is it absolutely necessary to have the IR filter in front of the detector removed and, if not, what filters in front of the lens could be used and secondly does anyone know of cold IR emitters which could be used to illuminate objects to be photographed at the macro level? Thanks for your help.

 

[GreenNinja67]

The first one I can answer Norman.

It's not essential to have the sensor filter removed but if you don't and add an IR filter in front of the lens the shutter speed will be too low to hand hold.

If you replace the sensor filter and use the same IR filter in front of the lens you will obtain "normal" hand holdable shutter speeds.


Hopefully someone else will be able to answer your second question.

 

[GreenNinja67]

You can use any filters in front of the lens from 590nm to 950nm but the darker the filter the longer the shutter speed will be.

I'd suggest trying a 720nm but using a tripod and cable release.

 

[Mr Perceptive]

I have two questions and I apologise in advance if these have already been covered. Firstly, is it absolutely necessary to have the IR filter in front of the detector removed and, if not, what filters in front of the lens could be used and secondly does anyone know of cold IR emitters which could be used to illuminate objects to be photographed at the macro level? Thanks for your help.

@Littletank - As @GreenNinja67 says, it is not essential to remove IR cut filter from camera, you can buy screw in filters to add to your lens, but the shutter speeds will become long. Also the IR cut filter on the camera will start to be more invasive the deeper into the IR that you go. At 720nm (Hoya R72 filter) you will probably get decent results but move to an IR850nm or IR940nm filter, your exposure times will become very long and possibly unusable. You may also have focus issues when you add the IR filter, as most camera will not AF through it, and the image may appear very dark in LiveView, so you might have to focus first, then add filter and recalculate exposure time. This does dep[end on camera though.

Regarding IR light sources, LED light sources are available, I work in industrial machine vision and we often use 850nm or 940nm light sources, but these are typically not cheap, as they are usually specialised units eg ringlights, backlights, etc (and made in small quantities), that said you can buy the individual LEDs on eBay and make your own light units. For very simple trial illumination you could use a TV remote control! Security light units are also available often at 850nm, giving low cost IR solutions eg https://www.ebay.co.uk/itm/96-LED-1...481608&hash=item41cc9e690b:g:D48AAOSwGshZewAy

Hope that helps

 

[nandbytes]

Firstly, is it absolutely necessary to have the IR filter in front of the detector removed and, if not, what filters in front of the lens could be used

So this depends on the camera (its not consistent even within the same brand).
One of the main benefits of removing the IR filter as already mentioned is that it allows you to shoot at fast shutter speeds and hence avoid long exposures and also excessive tripod use.
But some cameras are incapable of shooting IR even with long exposures (eg: my old Sony A6000). Then there are some cameras with a removable IR filter (sigma SD1) i.e. you can remove and add it back yourself.

But if your camera doesn't have a very strong IR filter and you are happy doing long exposures to start with at least, the hoya R72 filter is a good starting point.

secondly does anyone know of cold IR emitters which could be used to illuminate objects to be photographed at the macro level? Thanks for your help.

Erm... yes but they are expensive or you'll have to try building your own. If you tell us what you are trying to photograph and how maybe we can suggest something appropriate to your use case.

P.S. I am selling my modified/converted Sony A7 in classifieds