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Author Topic: measure anlges, distances, light  (Read 5703 times)
user
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« on: October 05, 2007, 07:48:53 AM »
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hello


I want to make some shooting and what I need to be able to calculate angles and distances accurately
are there any devices that can help me?

this is the scheme of the shooting:


I need to be able to measure the angles and distances accurately in order to find the optimums so that I will be able to reproduce them

also, I would like to measure the lighting

any ideas/suggestions welcomed


thanks
« Last Edit: October 05, 2007, 07:49:26 AM by user » Logged
jonstewart
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« Reply #1 on: October 08, 2007, 11:18:44 AM »
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What's the point of this setup? If I knew a little more I might be able to help.
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Jon Stewart

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« Reply #2 on: October 08, 2007, 11:57:33 AM »
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to shoot book pages in order to digitize books

are there any electronic spirit-levels and lasers that calculate distances and angles?
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Dave Carter
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« Reply #3 on: October 08, 2007, 12:08:32 PM »
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Maybe silly question - but have you considered flat bed scanning?  Or is the binding in the way?

For your approach, use some "story sticks".  They will make it easy to reproduce the same setup.  You will also need to put several pieces of white tape down on your desk to mark reference points.  I have had good luck this way.

Dave
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framah
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« Reply #4 on: October 08, 2007, 12:19:40 PM »
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First, something as a simple as a piece of string from the lens to the face of the book will tell you the distance.

As for the angles, a protractor or a drafting triangle will help you set the angle of the book. Say you wanted the book at a 45 degree angle, you would get a 45 triangle and use that to help you set it up.
You could also make a stand set at 45 degrees.

The more I look at your drawing, the more I think it won't work as well as you think. The page you are trying to shoot is above the spine of the book and will naturally want to bow out and fall. What you need is something that will hold the book upright and have clips to hold the page flat in the upright position. This way you can shoot both pages at the same time.

Your way would entail  shooting all of the pages of one side then reversing the book and doing the other side... THEN having to go back and recollate the pages so they are back in order.

Another possibility is to lay the book flat on the floor and then set the camera so it is shooting straight down, the way copy cameras are set up.

Once you have all of the distances and lighting and exposure times and such set you don't need to see into the screen.
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jonstewart
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« Reply #5 on: October 08, 2007, 12:23:27 PM »
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Yes, I was thinking it was a straight repro job, so there would be simpler ways of doing it . ie copy stand and means of keeping the pages flat. If the binding is a problem, then you support the side of the spread you're NOT shooting, and shoot from directly above, from a convenient reasonable height to minimise distortion.
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Jon Stewart

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« Reply #6 on: October 08, 2007, 01:01:59 PM »
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any recommendations or mathematical equations to determine the optimum angle, distance, light ?
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jonstewart
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« Reply #7 on: October 08, 2007, 02:57:04 PM »
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Quote
any recommendations or mathematical equations to determine the optimum angle, distance, light ?
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The way it's usually done is to lay the book flat and use two diffuse lights at 45 degrees either side of the plane of the book. The camera is perpendicular to the plane of the page ie directly above, with whatever lens set at about f8 (or whatever the optimum aperture is for THAT lens) If the book won't lie flat, one solution is to raise the side that you are not photographing and adjust lighting accordingly.

You must ensure even and controlled lighting of the page. Falloff in light that may not be noticeable by eye, will probably be noticeable in the photograph.

So, in summary, I still can't see why you are interested in distances and angles etc. Those are pretty much irrelevant to accomplishing the task.
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Jon Stewart

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papa v2.0
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« Reply #8 on: November 17, 2007, 04:13:26 PM »
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what types of books are you intending to digitize and for what purpose?

Once i know that i could recommend type of lighting etc and maybe some techniques
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user
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« Reply #9 on: November 17, 2007, 05:13:15 PM »
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thanks for your reply

I want to digitize text mainly, some diagrams (no high resolution needed) and few photos

I dont intend to do some professional reprography work, digitize art, scientific images, or something like this, so that I need ultimate resolution and accuracy

I just want to digitize regular scientific books, with mainly text and few diagrams and photos

the purpose is to save them as pdf files so that I cant easily search for specific terms in all of them and to display them in my portable ebook reader

what I need is as high as possible OCR accuracy (in order to minimize manual corrections afterwards) and regular diagrams and photos digitization

thanks
« Last Edit: November 17, 2007, 05:15:04 PM by user » Logged
Angst
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« Reply #10 on: November 25, 2007, 06:34:16 PM »
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Quick answer: lens should be 90 degrees (perpendicular) to page and optimally centered on the middle of the page. Take two pieces of thread and make an X from corner to corner and try to be 90 degrees from that point. Focus on the thread (a tiny bit ABOVE the printed page) and the page will be optimally focused. As stated before, lamps 45 degrees from the page plane and try to have them be equidistant (use a string) so the light is even from side to side. Don't shoot at the minimum focus distance for the lens, back off another 6 inches or more to get the sharpest image. Then shoot and don't worry about it: you will have done the "optimal" best you can with the equipment on hand.
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- Angst
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