Photography - 1

 Although point-and-shoot photography, provided by my smartphones, have served me well in the past, occasionally, I need to have more control and my study of biology has brought that forward, especially here in the desert where the intense light adds an extra factor and need for adjusting exposure.

So I decided to take Professor Marc Levoy's online digital photography course (Digital Photography). And I'm learning quite a lot.

Exposure, the amount of light reaching the photographic element affecting the brightness of the image, is a subtle balance of shutter speed, lens aperture, and ISO which is a measure of the sensors sensitivity to the light.

The trick is that each control involves a different trade off.

For instance, the longer the shutter remains open, the more motion you will catch and the more the subject will blur, which is an effect that you might want occasionally, but not usually.

These two scenes show what progressive shutter speeds will do to brightness.

If you expand the photos above, you can see that the dog is more blurred in the brighter (top) photo.

You can really see the trade off of motion blur and brightness in the photographs of the ceiling fan below  Only the shutter speeds were changed between photos.

Aperture width controls brightness but it also controls depth of field, the area a distance away from the lens where subjects are sharp. Only my Photon camera allows the virtual aperture to be changed and the differences aren't great, so that might be why the other apps don't provide the option.

Top right f/1 clockwise by steps to f/16. Expand each photo and you can see a difference in the sharpness of leaf veins 

ISO is the last element of exposure. It was originally a measure developed by the International Organization for Standards to describe how "fast" a photographic film was, that is, how sensitive it was to light. Since sensitivity was related to the graininess of the photographic emulsion used, it also was associated with the graininess of the image produced. That translated well into digital photography 

For a CCD, (photographic sensor) each pixel can be amplified to increase its sensitivity to light. That amplification also introduces noise. Enlarge the following photographs and note the "graininess" of the images.

An ISO of 100 is the image as it is produced by the sensor without any amplification. ProShot will adjust ISO from 100 to 19200 and those values are shown in steps above. The top left image has an ISO of 100 and the sequence gets brighter to the lower right. But enlarge the lower right image to see how grainy it looks, so there's a trade off. And you might want that graininess. I sorta like it 

Autofocus (automatic mode) adjusts everything for you and usually does a good job except for some special effects. You can even adjust depth of field in automatic mode on some cameras (like ProShot and Photon) by tapping on the part of a scene you want to have the focus.

Bracketing is a useful tool for planning a picture. It gives you a number of successive shots of the same scene with progressive exposures. The following shows three exposures differing by 2.2 stops.

So, before I go on to my second photography blog, let me tell you what Professor Levoy says about choosing a camera 

If you have the money, get an SLR (or DSLR) or MIL, not a point-and-shoot. 

Don't worry about megapixels, most cameras have too many.

Don't worry about brand or body 

Worry about lenses. Variable zooms are nice but consider the quality.

Avoid large focal ranges because they tend to be "soft".

Maximum aperture (lower f-stops) is good 

Some accessories you might want: 

50 mm f/1.8 "prime" lens for low light work

A good, light tripod isn't too expensive, and you might want a table tripod 

An external flash can be used to advantage. You can control where the light goes....and the shadows 

Video capability.

Now, that said:

Bryan Peterson's Understanding Photography Fieldguide is subtitled How to shoot great photographs with any camera, and for fieldwork I take it as gospel. For professional work, spend the money.