Saturday, November 19, 2005

35mm Adapter - Tests

ran a test of the adapter before epoxying and final assembly, just to check measurements and such.
this was done with the gg off and not rotating.

there is some chromatic abberation visible, which i am unclear to what is causing it. either the macro (which isnt an achromat) or the fact that there isnt a fresnel in front of the gg. i'll try both and see what helps.

the optura was place at two feet away and the test chart at three and three quarter feet away. lighting was just a 250 watt floodlight.

movie availible here (note: quicktime 7 required) 640x480 @ 2.3MB

Thursday, November 17, 2005

Image erection system - mirror calculations

how the heck do you figure out what size mirrors you use!?!?
well, the answer is the Pythagorean theorem.
yes, the very equation you learned in school.

so you have a 36x24mm frame size that you need to rotate 180 by going through four mirrors placed at right angles. let's take a look at one mirror set up at as such.

this is a view of my first mirror set up from above.
the 36x24mm image comes in through side A, reflects off of the mirror placed at side C, and exits at side B. this makes a horizontal 90 degree reflection.

since side A and side B form a right angle, this allows us to use pythagorean's theorem to calculate the mirror side, side C.

we know that the image is 36mm wide, and will stay that way.
both entrance and exit frames of the triangle will be 36mm
so that means, A=36 and B=36.
when we plug them into pythagorean's equation, we get the square of C.

36^2 + 36^2 = C^2 = 1296 + 1296 = 2592

now we just square root it and get the length of C.

sqrt 2592 = about 50.9mm (roughly 2")

so we have the length of the mirror, the height of the frame stays constant.
the result is a 50.8x24mm mirror.

we have two mirrors that do this horizontal translation. the first and fourth mirrors.

the second and third mirrors do a vertical translation
instead of a triangle where A=36 and B=36, the sides will be A=24 and B=24.
referring to the image, this would be the 2nd or 3rd mirror as viewed from the side.

same equation

24^2 + 24^2 = C^2 = 576 + 576 = 1152

now square root the result.

sqrt 1152 = about 33.94mm (roughly 1.33")

complete the mirror spec by adding the horizontal length that stays the same.

33.94x36mm mirror size.

Image erection system (cont.)

just more concept pictures with a zr80.

adapter (box) < system < zr80 (any camera)

I drew an "F" rotated 180 degrees on the box, and this is what you get.

close up of the zr80 meeting the system

yep, thats a lens TAPED on. its a lens meant for the viewfinder of an slr. it sits on top of the focusing screen.

Wednesday, November 16, 2005

Image erection system

so i got my front surface mirrors in on monday, and i just finished the image erection system.
it consists of four front surface mirrors placed in a way that will rotate the image 180 degrees.
it's purpose in the adapter is to flip the image optically so that you'll view and record an upright image.
the main disadvantage of the addition of an image erection system is that it will add roughly 120mm to the optical distance from the ground glass to the camcorder lens.

custom cut mirrors: $28
wood: $free
epoxy: $3
metal bracket thingy: $free
total cost: $31

top view

36x24mm frame size as seen through the mirror system. the digital camera i used was limited to 3x, so it didnt fill the frame.

rear view

front view