Photographs by Frank

24 June 2019

More Experiments

Filed under: Garden Flowers,Summer,The "New" Yard & Environs — Tags: — Frank @ 11:00 PM

I have a shoe box full of random lenses mostly salvaged from various devices over the years. This afternoon, I took the usual lens out of the camera obscura and tested each lens from my box by holding it up to the opening in the box. Most of the lenses resulted in horribly out of focus images and will require more work — making lens tubes to fit them, etc. — to see if they can be focused on the ground glass.

However one lens, a single convex lens (flat on one side and convex on the other), in a convenient aluminum frame threw a decent image when held against the opening. I taped this lens in place and headed out to the yard to experiment. I did not stay out too long as the mosquitoes were fierce.

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23 June 2019

Experiments with Slits

Filed under: Monadnock Region,Summer,The "New" Yard & Environs — Tags: — Frank @ 7:30 PM

We had nine cords of wood delivered on Thursday. Thus, these days, I spend my mornings stacking firewood. I am trying to do about a cord each day.

Afternoons, however, are for experiments.

These photos were made by replacing the lens in my camera obscura with a slit made by placing two razor blades very close together. The slit acts similarly to a pinhole in forming an image, except that the image is stretched out along the length of the slit. I have placed the slit on the camera (with tape, nothing fancy!) at a roughly forty-five degree angle.

I took my experiment for a walk around the yard just to “get a feel” of what it might do,

The viewfinder of the digital camera is very dim; I can often see only a couple of the brightest spots in the scene. Thus framing is imprecise.

By cranking up the ISO as high as it goes (3200 on my little Nikon 1 V1), I can get a reasonable shutter speed; 1/4th to 1/20 of a second. I deal with the horrible noise this causes in the computer, but since nothing is really sharp to begin with heavy noise reduction seems to work fine.

I will be as interested as anyone else to see where this experiment leads!

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17 August 2013

Experiments in Optics

Filed under: Garden Flowers,The "New" Yard & Environs — Tags: , — Frank @ 6:00 PM

I recently acquired a bunch of lenses from old enlargers… both enlarging lenses and condenser lenses. One of the largest lens in the collection is a 5″ in diameter condensing lens that is mounted in a metal frame. It is probably from a 4″x5″ enlarger. Today, I decided to “play” with this lens in conjunction with a digital camera.

Here are the first results…

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The last photo in this set shows the set up. I mounted the condensing lens on a tripod, added a cardboard lens hood (which you can’t see in this photo) and a dark cloth. Both the hood and the cloth are attached to the lens with masking tape. The first couple of images I tried were low in contrast and had lens flares. Thus, I added the lens hood.

To use this set up, I placed myself and the digital camera under the dark cloth and made photos of the lens.

Clearly the middle of the circular frame is the sharpest, but it will never be “tack sharp”, and that the images goes soft and distorted towards the edges. All of which is really the point in something like this. Isn’t it?

It was interesting to watch how the image made by the lens changed in large ways with small movements of me and the camera. I learned quickly to make an exposure when the composition was good and not try to worry about stuff at the edges of the frame that were going to get cropped out any way.

Post-processing consists basically of cropping to the square format (to eliminate the extraneous part of the frame ) and  adjusting the exposure to make sure that the frame is pure black). A few images got small amounts of other processing (curves adjustments, etc.) but nothing major.

I forgot how hot it gets under a dark cloth in the bright sun… even on a day when the air temperature is in the low 70’s. However,  I think that results were worth the “suffering”! What say you?

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