Category Archives: Sensors

Is a Kit Lens Better for Infrared Photography?

Okay, I have a digital camera converted to capture infrared light. I’m ready to go out and shoot pictures, right? My camera is ready–Is my lens?

Light is bent when it passes through transparent materials such as air, water, and glass. However, different colors (wavelengths of light) may not bend at the same degree so water droplets and prisms make rainbows by spreading out the mix of frequencies of light at different degrees. A lens bends this composite of colored light towards its focal plane, our camera sensor or film. It is shaped and coated with materials that eliminate the spreading out by different colors of light.

sample-hot-spot-dsc_0083
A premium Sigma 17mm-50mm f/2.8 lens at f16 produces a hot spot which I have exaggerated with a curves adjustment.
sample-kit-lens-no-hot-spot-dsc_0207
A Nikon 18mm-55mm f/3.5-5.6 kit lens at f/8 did not produce a hot spot. I have applied a similar curves adjustment which would have revealed an appreciable hot spot if it had been there.

My subject is in focus–what’s the big deal about infrared light? Camera lenses focus the visible spectrum. Some lenses also bring infrared to the same focus as visible light. Others don’t do as well and may produce a hot spot on the image.

Compared to pro lenses, a kit lens may not be able to produce as sharp an image in the visible spectrum, but may focus infrared frequencies more accurately. Look here to read a list of some lenses which have been tested for infrared photography.

“Good” and Cheap

wetland-reflection-1-PA260181I believe digital cameras, their sensors, lenses, and image processors have evolved and multiplied enough that I can buy equipment to make “fine art” for not a lot of bucks. However, I don’t think full frame cameras, professional lenses and the like are without value. They’re tools in talented hands for making extraordinary images.

 

My point is that I don’t need spend like crazy on high end gear to make photographs that please me and whatever audience I can gather.

 

After one or two newer model generations have gone to market, leftover inventories may be steeply discounted. I look at specifications. A pro-grade camera may share technology with a lower priced model. Hey, if I can control aperture, ISO, and exposure time, then I’m happy.

 

I think of this approach as buying trailing edge technology. Maybe it’s just my Yankee stinginess. Whatever it is, I save by buying things that give me raw files, high resolution, low noise, and that satisfy my fussy eye without breaking the bank.

 

What is enough? I must be happy with the work that I create. If doing photography doesn’t give me joy and satisfaction, it won’t matter what I spend.

Numbers, part three (Conclusion)

Sensitivity is defined by the International Organization for Standards (ISO) in its abstract thus:

“ISO 12232:2006 specifies the method for assigning and reporting ISO speed ratings, ISO speed latitude ratings, standard output sensitivity values, and recommended exposure index values, for digital still cameras. ISO 12232:2006 is applicable to both monochrome and colour digital still cameras.”

ISO 200 (low noise)
ISO 200 (low noise)

Long ago we used to call this the ASA, which was the similar method for determining film sensitivity from the American Standards Association.

The lower the ISO number is set the longer it takes to record an image; and the less noise appears in the image files; higher ISO’s make faster recordings of images with more noise. Camera image processors have improved noise reduction so I may select higher ISO settings with little noise in my image with recent digital camera models.

Click on images to view at full size for better comparison of noise levels in the two images.

ISO 16000 (high noise)
ISO 16000 (high noise)

Methods of noise reduction include blurring or smearing small artifacts, subtracting pixels based on another exposure, and so on. Perhaps some small details get lost in the process. Although, details may be recovered using the algorithms used in the camera image processor or post processing. Some pixels in the resulting image thus may be made by firmware or editing software rather than light.

In summary, I can apply three basic camera settings: aperture, time, and sensitivity to make creative choices such as sharpness, and blurred or frozen motion. I can compensate for the lighting; I can select high sensitivity for low light exposures, and low ISO settings for cleaner, more detailed images.

Making choices with these settings lets me capture how I see a thing and share it in a photograph.

Film & Sensor Sizes

The naming scheme for digital camera sensors is derived from old television camera sizes expressed as the diameter of the tube through which light enters to strike the sensor at the end of the tube. The sensor’s diagonal measurement is about one third less than that of the tv camera tube so camera sensor diagonal measurements are smaller than you might expect from their names.
43-sensor010
Camera with a Four Thirds Sensor: Micro Four Thirds cameras are mirrorless.
Here are a few film and sensor dimensions, and their relative sizes compared to 35mm film and full frame digital sensors.
Type Format Dimensions (mm) Surface Ratio to 35mm
Width Height mm²
film 4×5 121 97 11737 1358%
film 645 56 42 2352 272%
Sensor 645 43.8 32.8 1436.6 166%
Sensor Full Frame 36 24 864 100%
Sensor APS-C 22.3 14.9 332.27 38%
Sensor four thirds sensor 17.3 13 224.9 26%
Sensor 2/3″ 8.8 6.6 58.08 7%
Sensor 1/1.6″ 8 6 48 6%
Sensor 1/1.8″ 7.2 5.3 38.16 4%
Sensor 1/2.7″ 5.3 4 21.2 2%