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Old September 25th, 2002, 09:45 AM   #16
 
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Dre, I have to agree with Jeff. I've never pretended to know, much less understand, all the math and physics that come with photography, especially lenses. However, as I said earlier, I've been making images for over 30 years. The basic fact remains, wide angle lenses have an inherently deeper depth of field than normal or telephoto lenses.
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Old September 25th, 2002, 10:04 AM   #17
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Barry, what you experience is well knowm with those small CCD's. See http://www.mini35.com/ if you realy need DOF that matches 35mm film.
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Old September 25th, 2002, 10:11 AM   #18
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Jay, plse make (once again after all those years..) a test setup like two resolution charts at different distances and compare (for the same scene size) the zoomed-in and the zoomed-out pictures...
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Old September 25th, 2002, 10:18 AM   #19
 
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Dre, no need to do more "tests." I know what I get and I know what my lenses can and can't do. Looks to me like you're trying to "sell" something. I ain't buying.

In all those "samples" on the mini35 site, there isn't one shot I can't duplicate using the lenses I already own.
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Old September 25th, 2002, 10:39 AM   #20
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Jay, of course you can't duplicate..that Dof adapter is not a "lens" but an image (re)projection concept
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Old September 25th, 2002, 10:45 AM   #21
 
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You misunderstood what I said. I CAN duplicate the images they show using my exisiting lenses WITHOUT their adapter. I have shot similar images with comparable depth of field on several occasions.
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Old September 25th, 2002, 11:23 AM   #22
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Alright. Didn't mean to start a war. I was just hoping that if I did get a converter, I wouldn't have to take it off. . .like ever.

That's cool though. Thanks for the advice. And play nice.
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Old September 25th, 2002, 11:35 AM   #23
 
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Sorry, Dre, and Josh, I just get a little riled when I'm told something can't be done and I've been doing it for years. Apologies to all!
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Old September 25th, 2002, 11:48 AM   #24
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I'm simply looking for a solution for all situations. Attach a wide angle converter to the 16x lens and you get the best of both worlds (partial zoom, that is, 10x)
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Old September 25th, 2002, 12:11 PM   #25
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You have to make the choice that's right for ya.

The main hassle with adding a WA adapter to either 16x lens, is that you're making a front-end heavy camera even more front-end heavy.

The advantage of the 3x lens is that it's a lot lighter and easier for hand-holding.
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Old September 25th, 2002, 12:26 PM   #26
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Sorry Jay for my misreading. Only one question, just for my own knowledge, and then I'll stop discussing. Could you plse inform me what the CCD size and the F-number is you use for getting those simualar images? FYI I have been heading lens design for about 25 years, so, maybe I have some background too..
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Old September 25th, 2002, 02:14 PM   #27
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dre. . . . . .

You mention only 2 factors in determining Depth of Field. <<< Only the F-number and the target(CCD)dimensions determine the DOF>>> You need to reread Nicholas Sushkin's Depth of Field Calculation. The thin-lens equation takes into account focal length and distance to the subject. In DoF calculations in this country we usually don't use the term f Number. What is used is the effective aperture (or size of the opening of the diaphragm). It is a size for example 12.5mm, not F2.8. The effective aperture, 12.5mm is divided into the focal length, say 25mm and the relative aperture is F2. The information below is from the post I suggested you read. It is the way depth of field works and it is in agreement with Nicholas V. Sushkin, the author of the DOF plotter you referred to previously.

Depth of Field (DOF) is dependent upon the following variations:
a. The focal length of the lens.

b. The diaphragm opening (effective aperture, not F-number).

c. The distance from the lens to the object that is focused on.

d. The distance from which the image is viewed.

e. The viewer's personal standard of the permissible degree of sharpness (or unsharpness).

Other variables remaining constant, it follows that:

a. The shorter the focal length of the lens, the greater the DOF.

b. The smaller the diaphragm opening, the greater the DOF.

c. The greater the distance to the object being focused on, the greater DOF.

d. The greater the distance from which the image is viewed, the great the "apparent" DOF.


Jeff
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Old September 25th, 2002, 03:01 PM   #28
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Plse instead of going on with pseudo math. Check it and see if you can change DOF if the scene (subject) size remains constant and you zoom in and out, and of course adapt your shooting position to get the constant imag size. I demonstrated it several times to non scientifically skilled people.
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Old September 25th, 2002, 03:07 PM   #29
 
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Dre, when I want to reduce the depth of field (using the XL1s) I will set the gain at -3db, turn on the neutral density filter (additional NDs may be added if needed) and add a polarizing filter to help intensify color saturation. All this usually gives me an f-stop of between 2.8 and 3.5, depending on the lighting.

Going back to the shots on the mini35 web site. I would just about guarantee than most, if not all, of those were shot with a lens that would fall into the "telephoto" category. For example:

- The man and children feeding the birds
- The railroad yard shot through the fence
- The close-up on the branch panning to the kid on the bicycle
- The shots of the trees
- The fountains

The remaining two or three shots are questionable. But any of the above can be duplicated with the lens on the XL1[s], because I've done it, as I'm sure others have, too.

Telephoto lenses, as you well know, appear to compress the depth of space in images. You can photograph items fairly spred out along an axis perpendicular to the front plane of the lens, and yet when shot with a telephone lens, they "appear" to be closer together than they really are. All the images listed above have that trait.

No reflection on you, but my life's experience has shown that many designer have little appreciation for the vast possibilities for implimentation of the tools they've designed. My point is, the scientific design and the creative application don't always coincide.
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Old September 25th, 2002, 03:23 PM   #30
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I didn't realize my degree in Physics made me non scientifically skilled. I'll ask for my money back.

Jeff
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