Some experiments with IS Pro spectral response

            Using an uncoated DVD as a reflective diffraction grating and the late afternoon sun as a light source, I experimented with different filters in an attempt to gauge what the IS Pro responds to.

Owing to the way the DVD split the light it was impractical to run UV and IR tests with identical setups. 

The top section starts with the unfiltered 'visible' response, with the blue end cropped due to the limitations of the experimental method. Cyan through to red are obvious, then there appear to be orange-ish and violet-ish sections within the IR response. The second test shows the response with a Marumi UV/IR cut filter. The orange section of wavelengths longer than red has disappeared, but there is clearly some blue and green from higher order diffraction, which explains the odd colours in the first experiment.

The next three lines show the response using cheap lowpass filters of 720nm, 850nm and 950nm. 720nm filter clearly shows the orange and purplish-grey response areas, tailing off in brightness with increasing wavelength. The 850nm filter provides a useful wavelength reference. In order to see any response from the 950nm filter it was necessary to increase the sensitivity from ISO 100 to ISO 1600. The implication from the results seen here are that the sensor responds quite a long way past 950nm but that its sensitivity is very poor at those wavelengths. I cannot explain the 'dip' in the middle of the 950nm response or the similar 'dip' in the orange part of the 720nm response.

Rearranging the experimental setup to show the visible spectrum somewhat better, particularly into and beyond blue, I then tried the UV response using a Baader U (2") filter. Note that it was necessary to change the exposure from 1/800s to 1/20s to obtain useable brightness through the UV filter; I suspect this is why the response appears to be beyond the lowest threshold of blue response. I suspect that the response shown here is only representative of the lower part of the Baader U's 320-380nm response. Although the Series E lens works after a fashion at near-UV wavelengths it is far from an optimum choice for this test. I did not test the UV setup with the Marumi filter, which would have given an indication of where 'blue' stops and 'UV' response begins; that is a project for another day.

These experiments have demonstrated that the IS Pro has useful sensitivity in non-visible wavelengths but does not give quantifiable results owing to the lack of calibrated references.

Taken on: August 26, 2013

Tags:

experiment

IS Pro

infrared

fullspectrum

Marumi

Baader

Baader U

frequency response

spectrum analyzer

spectrum analyser

bandpass

lowpass

720nm

850nm

950nm « less

Sets appears in: • Infrared and ultraviolet experiments

Groups appears in: • Lasers, HV & Optical Curiosities • Ultraviolet Spectrum <400nm more » • FUJiFILM FinePix IS • Infrared UK & Ireland • Infrared Photography • UV IR Fujifilm Finepix IS PRO • Full Spectrum Photographer « less

Camera: Fujifilm IS Pro, f/16.0, 1/8000 sec, 35mm (=53mm), ISO 100 (more info) (hide info)

Camera:	Fujifilm IS Pro
Aperture:	f/16.0
Exposure Time:	1/8000 sec
Focal Length:	35mm (35mm equivalent: 53mm)
ISO:	100
Exposure Bias:	0 EV
Flash:	Off, Did not fire
Exposure Program:	Manual
Exposure Mode:	Manual
Metering Mode:	Center-weighted average
White Balance:	Auto
Saturation:	High
Color Space:	sRGB
Software:	Digital Camera IS Pro Ver1.01
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