[anemone]

In digital the IR/UV is required to tell the sensor what it is wanted to be sensitive. Sensor actually doesn't care if it is red,blue, IR or UV. It just reacts to it.

The AA filter has been removed from most modern cameras so that people can get their moire and the last ppm of details. Pentax shakes the senor to make AA-filter if that is wanted

[varky]

Apparently the sensor in my K-110 is quite IR sensitive. I need to finally get a 720nm filter and test it, since I've been interested in IR photography for years now...

[lotech]

Then what is the difference between a K1, K3 both without the filter and the Sigma with a user removable filter ? also the Canon 5D SR that specially designed for IR photography ?

With regard to the filters my understanding is (please correct me if I'm wrong) that digital cameras generally have a low pass filter and a IR/UV cutoff filter in front of the sensor.

The low pass, or anti-aliasing, filter is there to reduce 'moire', but can reduce sharpness. The K1 does not have this filter as anti-aliasing is achieved by moving the sensor instead. Interestingly the Sigma SD14 doesn't have one either due to it using a Foveon sensor, instead of the more usual Bayer sensor.


The IR/UV filter restricts the light reaching the sensor to the visible spectrum, The filter is usually affixed to the sensor and in an IR conversion it is physically removed. In the Sigma SD14 the filter is located just behind the mount, and can be popped out with a finger. There was an old article in Popular Photography which discusses the Sigma SD14
.

Hope that helps,

Fred.

[lotech]

I took some test shots with my K3 and got similar result as my K7, since I no longer have the K7 I can't compare their IR sensitivity, but I am sure the K3 surpasses the K7 as I can handheld shoot in day light, I can see the metering working although it can't produce correct reading under IR. But strange that I got better result with my LG cell phone with the same IR760 filter, the LG has much higher IR sensitivity that I can have live view, where I got a dark screen on K3 I must put it on a tripod to take usable shots, the only thing bad about the LG is serious hotspotting, I got white streak light at the bottom occasionally on the K3. This is just for fun I never serious about IR photography, but I am quite interested in the Sigma SD QH longing to try out the Foven sensor, but since it got very limited ISO and dynamic range so it won't be my everyday camera, my dream still the K1 go first !

[VoiceOfReason]

The K5 was very usable in LV, but the shots were too long for handheld.

[pxt]

K3 II is good for infrared photography without modification?