cole_petersburg

I've also heard that the base on these films require a temperature of 250ºC (450ºF). I've had great luck with 90-proof brandy, but Everclear didn't have as high a flame. There's no smoke so you can burn it anywhere. It's likely that the difference between an ethanol fire and a methanol fire would only be temperature.

Oh... you want to capture invisible exhuast flames in daylight? That's difficult. I captured the brandy and everclear pictures in the visible spectrum with exposures of, like, 30 seconds.

Aha! I knew taking Quantum Physics would pay off. Attached is a graph of the intensity of the infrared light at 900ºF. The peak wavelength is way, way longer than what infrared film can pick up. The infrared light from the sun, along with the visible light, will probably drown out the flames.

With the proper equipment (probably not film, and maybe a refrigerated camera), you could make amazing pictures.

Quality is, of course, qualitative. I'm guessing at 4MP you would notice a difference on a 4x6 print zoomed vs. walking closer to the object. That's up to you.

 

First of all, digital zoom is simply cropping and resizing. You can do it in Photoshop. You could shoot wide, and decide on your composition later. This would be considered by many to be a lazy method of photography, at least for artistic photography. Digital adds responsibility along with choices.

 

Magnification numbers are usually taken to be linear, so half the distance with the same aspect ratio gives you 1/4 the pixels. 1 MP. At 5x, it's 0.16 MP. Pretty bad, eh?

 

Then there is the consideration of the _method_ of resizing. Your camera manual probably doesn't tell you how it performs the resize, but Photoshop will give you a choice between Nearest Neighbor (bad), Bilinear Resize (Good for shrinking) and Bicubic Resize (Good for enlarging). To visualize the difference between these methods, make a 3x3 pixel image in Photoshop, draw a checkerboard pattern, and enlarge the image by a factor of a hundred or more.

 

Then there's the resize method of your photo lab. They may do it worse or better. Their printer's native resolution may be a multiple of your photo's resolution or it could be way off.

 

Use your optical zoom or your legs.

The factor of two is an approximation. It's an extraordinarily good one at the hyperfocal distance for all focal lengths.<BR>

However, the hyperfocal serves us in other ways. It tells us depth of field for any focusing distance. The DOF markings on a manual focus lens barrel are found using the following equations.<BR>

Of course the depth of field acceptable by convention may not be acceptable by you, and the correlation may vary with focal length. E.g. I now stop-down my 28mm Yashica lens by one stop to get acceptable DOF after getting some blurry prints.

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According to http://www.outsight.com/hyperfocal.html#math,<BR>

H = (L x L) / (f x d)<BR>

NF = (H x D) / (H + (D - L))<BR>

FF = (H x D) / (H - (D - L))<BR>

f is f-stop, L is focal length, D is distance, d is the diameter of the circle of least confusion. By convention, d=0.03mm on a 35mm frame.<BR>

Here's something I'll throw in just because it was so hard to figure out because no one will explain it: Light travels from each point on your object in all directions, and travels to your circular lens in the shape of a cone. The light from each point is spread out among concentric cones. The lens shapes the cones and finally makes them converge on your film plane. The intersection of each cone and the film plane is the circle of least confusion, which you'd like to be sufficiently close to zero diameter. AND because the cones are concentric, stopping down the aperture eliminates some outer cones of light from each point, therefore stopping down does not crop your image.

www.dr5.com can process Ilford HP5+ at ISO 3200 as a B+W slide.

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I tried Tri-X at 800 and the results were great. A little pricey for slides. Caveat: I haven't tried HP5+ at 3200.

"So what the film alternative to my solution? Shoot negs of the prints and have many prints made of each?"

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Um, why not just keep the negatives in the first place? A negative is analog and physically simpler than a CD. Therefore it will keep both its physical integrity and usability longer.<BR>

Also, one uses a print and archives a negative. With a CD, you're using the archive every day, unless you make lots of copies, which gets very space-consuming.<BR>

I don't know what happens to your CDs, but I can't seem to keep a CD more than a year or two without getting scratches in the foil. Scratches on the bottom side appear within two months. I'm trying to keep them in jewel cases, but they take up so much space that I frequently just leave them on a spindle.

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Imagine what would happen if I left a spindle of CD-Rs to my descendents, or boxes upon boxes of jewel cases!

Did you mean short-focus or short-focal-length?<BR>

Coverage of the object or coverage of the film? Coverage of the film can be somewhat qualitative due to darkening at the corners of the image circle. Coverage of the object is simple.<BR>

Focal length vs. magnification is an iron law.<BR>

1/f = 1/i + 1/o<BR>

m = i/o<BR>

This means that the ratio between the size of your field of view and the size of your image on film is the same as the ratio between the distance from lens to image and the distance from lens to film.<BR>

Focusing is a matter of changing 'i' and 'o'. To focus closer, simply move your lens farther from the film plane and closer to the object. You're only limited by the size of whatever's keeping out stray light. When focusing really close, match out for the inverse-square light-falloff stuff.<BR>

Normally you don't notice it, but changing the focus setting changes the magnification slightly. When the distance from film to lens is the focal length, infinity focus is obtained because the reciprocal of infinity is zero. Don't say that to a mathematician.<BR>

However, some optics whiz figured out that you can design lenses to have an asymmetric lens diagram. A long, skinny triangle of light goes in, and a short, fat triangle of light travels to the film. This means you can mount a 300mm telephoto, say, 150mm from the film.<BR> Likewise, a 19mm superwide lens can be mounted on an SLR even if the lens isn't physically 19mm from the film plane. This is called retrofocus. For both types of lenses, the thin lens equation above no longer applies. The magnification is still the ratio of the sizes of the object and image.<BR>

I've heard of telephotos for LF, but beware: if you tilt it, the result will be out of proportion to what you'd expect because it's asymmetrical. Or something like that.<BR>

Hmm my 75-150mm telephoto for 35mm, when reversed, gives really close-up, high magnification. And somehow the zoom mechanism acts as a focus mechanism! Not sure how that works. I guess it changes the focal length - a whole new use for the lens equation. My 28mm gives higher magnification than the 150mm, but the lens barrel moves the lens in relation to the mount, so it's necessary to move the whole camera to achieve focus. I guess the telephoto, when reversed, becomes a retrofocus by definition.<BR>

Aha! I might actually answer one of your questions this time: When you reverse a symmetric lens, you get the exact same thing, unless only one side of the lens is coated. If you reverse lenses mounted in a lens barrel, you usually lose infinity focus because you can no longer get the lens back far enough. Not a problem for LF.<BR>

The difference in shutter speeds is a factor of 2^(1/3), or the cube root of two. A doubling of exposure is a factor of 2, which is one stop. 2^(1/3) is 1/3 stop. Over-or-underexposure of most films by this factor is supposedly the smallest increment of exposure that can make a difference in the density of the developed image. With print film, it doesn't matter much.<BR><BR>

50 * 1.2599 = 60 100 * 1.2599 = 125 200 * 1.2599 = 250, etc.<BR><BR>

For more exact exposure, when the meter says 1/60, your camera will overexpose by 1/3 stop at 1/50th, so squeeze down your aperture 1/3 stop. Alternately, you may be able to tell your meter the film is 1/3 stop slower, so with ISO 20 and 1/60th your meter will give you the correct aperture setting for your ISO 25 and 1/50th.

f-stop = f/ap<BR>

4 = 300/75<BR>

300 * [sqrt(2)=1.41] = 424.264<BR>

424.264/75 = f/5.6<BR>

f-stops are called 'relative aperture' because they are relative to your focal length. If your focal length changes while your aperture settings stay the same, your f-stop will change. Your lens barrel will still read f/4 because it only sets the absolute aperture.<BR>

The second series of f-stops is correct. Each f-stop is a multiple of the square root of two.<BR>

A=pi*r^2, so multiplying the absolute aperture (that's the diameter) by sqrt(2) will double the area of the aperture circle, thereby doubling the amount of light going through the aperture. I'm not sure what units "amount of light" comes in. Lux or foot-candles or something.<BR>

If you're saving money, you're probably not looking for a camera with resale value. In that case, you could simply cut down the film wind lever. You don't need all that much torque to wind the film.<BR>

Just a random thought.

Ja, dat German metal! Perhaps it's germanium. The metal probably did block the x-rays, although not as well as lead might since it has smaller atomic nuclei. I guess it's good to have a metal shutter! X-ray scanners detect knives and guns because metal blocks x-rays.

I've read a lot of anecdotes on this site about x-ray fogging, but I've never seen a picture of it. Could someone please post a picture that has been noticeably fogged?<BR>

The other day I took some Fuji Superia 1600 ('Protect from x-ray' on the box) through two airport security scanners (marked 1000 ASA and 800 ASA, not the new machines) and will take it back through before having it developed. I hope to have something really nasty to post here.

http://www.acecam.com is a good index for finding stuff. I found Overlake Photo in Bellvue, WA

http://www.overlakephoto.com

I have a Lubitel which cost me $30<BR>

I saw a Mamiya SLR on Photo.net that costs $3650<BR>

Will the Mamiya make better looking shots than the Lubitel? Yeah, some of the time. Will I have more shot opportunities with the automatic settings on the Mamiya? Yes. Will 210 times as many shots turn out right? No. Will my shots be 210 times better? No.

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If I had saved up for the Mamiya, I would have missed a lot of photo opportunities. I can take more photos with the Lubitel than with the Mamiya. One picture is much better looking than zero pictures. <BR>

I dunno why they're so expensive, but even if the engineering is worth it, I'm not gonna pay that much.