Sigma SD14 Channel Response under Various Filter Combos (Done!)

[Andrea B.]

Raw Digger pointer: I wanted to mention to any RD novices*, that if you use Raw Digger to look at photos made with narrowband filters (spiky histos) or to look for oversaturation (hitting the right wall), then setting the y-axis to log values helps the display of data you might just miss if using a linear y-axis**. The examples above where I've posted both linear and log versions help illustrate this.

 

 

 

*me, for example. I'm still learning things about this app!

 

**Experienced chartists know this kind of thing but I tend to forget it myself.

[dabateman]

Do not forget that the Sigma SD14 cameras have a hot mirror that cuts in at 420nm. The image sensor has a glass cover of unknown transmittance. There are micro-lenses that also have an unknown transmittance. Then the first junction (blue) has a this layer of silicon to attenuate the UV & only allow the blue photons to enter. This all comes together to make the Sigma SD14 very unattractive for UV photography !

I have to mention the lens too has some limitation to UV as well.

Even removing the hot mirror & having a suitable lens, there is still the restriction on UV penetrating the cover glass, the micro-lenses & the top layer of silicon !

I am a big Sigma fan, but that is the limitations of it, not a go-to camera for UV ! Great for RGB & IR.

Cheers

Col

 

Maybe some confusion here. The SD14 was the 3rd Sigma camera made and first with new 4.7 mp sensor. It has microlenses, and maybe coverglass on top. The uv/ir block filter is the dust cover and it is easily removed. All my images are without the uv/ir blocking dust cover.

The SD15, SD1 and all Dp models have a metal substrate layer on top of sensor to improve high iso. The SD14 does not have this layer. I don't know about the Quattro cameras and will test the SDQ next week.

Jonathan has recently shown that microlenses improve UV sensitivity for a Canon camera. So they may not be a limiting factor.

Jonathan has also showed that his SD14 was sensitive to 350nm. I can see with a 340bp10 filter. But its not great. So I would place the limit about there as well.