cole_petersburg

August 12, 2004

I have a Contax lens on a Yashica body because it's great for manual focus, manual exposure, and it's a cheap combination. It doesn't seem right for you.

Why do you need the best glass? If you're just getting 4x6 digital drugstore prints, you don't need nice glass. You don't need a camera which is appreciated.

Contax bodies don't seem to be popular. Chicken + egg.

August 9, 2004

Paul Simon sang about a Nikon in "Kodachrome."

I always base decisions on song lyrics. Apparently some prefer wars.

August 4, 2004

I recently bought a macro coupler. It's a male-male filter-ring adaptor so that the second lens is reversed. Because one of my two lenses with the same filter size is a zoom, I can actually focus by zooming instead of by moving the camera. All I get is a dim circle in the middle of the viewfinder, and changing the final aperture ring changes the size of the circle. I think the in-focus point may be near that ring. No results yet.

Your magnification is the ratio of the focal length of the forward-facing lens to that of the reversed lens.

August 2, 2004

1/50th differs from 1/60th by one-third of a stop. Frequently insignificant.

I wish they would just go with powers of two.

July 29, 2004

Ron, will you sell me your film when Kodak discontinues theirs? :)

July 28, 2004

I've frequently had bits of fog on 120 film, along the whole length, almost never intruding into the frame. Efke 25 most recently. Maybe it's a reflection off the black plastic reel.

July 25, 2004

Oh, yah!

It's called a lens hood. Get a lens hood for a long lens and put it on a normal lens. For a more graduated look, just get a very, very old lens.

If you have a Lubitel, crank the aperture control all the way to f/64. Just kidding - you don't have to do anything to achieve this effect with a Lubitel!

July 23, 2004

> Is there a night-time equivalent to the "sunny 16" rule?

> The "moonie minute," perhaps?

Because of reciprocity failure and logarithmic nature of exposure times, it's difficult to overexpose a nighttime shot. Lights tend to be streetlights or stars so they usually won't cause the whole image to be overexposed. Those pictures of streaking taillights always seem to retain dark pavement and buildings. Just open your shutter and leave it that way for a while!

July 21, 2004

You should be able to find a static page about this.

f-stop = focal length / aperture diameter

They go up in multiples of the square root of two because A=pi*d*d/4. That means that multiplying the diameter by the square root of two doubles the area covered.

The wider the f-stop, the shorter the DOF.

http://www.outsight.com/hyperfocal.html

July 17, 2004

I love the looks of Kodak 1600P slide film and Fuji Superia 1600.

July 16, 2004

>> The modern world has only achieved technology.

I think you're looking at the wrong time scales for progress, Trevor. 25 years as opposed to 250.

Not only do we have democracy and allow the poor, the ladies, and people of every race and creed vote (most of the time), but we've popularized it around the world. We have public education (such as it is) instead of education only for the rich. I haven't read anything about freedom of religion for the ancient Egyptians.

Sure, we're lazy, ignorant ingrates, but is that not inherent in our nature? I don't think we can expect that to change any more than our creativity in choosing what to photograph.

July 13, 2004

A common problem I've had is the printing. Fortunately, you can have those redone. Don't take astro photos to a drugstore, as they'll come out gray.

As for negatives, the only problem I've ever had was some water-soluble streaks on the negs. The machines are automatic, so the chemistry shouldn't be far off.

May 7, 2004

I would suggest being careful when melting plastic bottles. I tried melting yogurt tubs once and they fused together, but they oxidized, gave off noxious gases, and ended up very brittle. Perhaps you could put them in an oven with a lit candle or something to heat them with less oxygen.

April 29, 2004

R&D costs in aerospace are definitely far higher than those in the automotive industry. A huge amount of materials engineering and research goes into making an airplane: Nickel superalloys for the turbine blades, aluminum alloys for the skin, magnesium castings, titanium-silicon carbide composites at $11,000 per kg, etc. It's similar with bicycles; they didn't invent a new shape, just a new material.

Automobiles, however, have strict cost requirements due to huge demand. Therefore they are made of steel, and use stupid, stupid pistons.

I doubt that LF cameras use exotic metals, and the mechanical design complexity is probably about the same as with a 35mm SLR. The difference is the economy of scale, plus, the guys who build it probably shoot LF! They need the money to buy film. Nobody's going to build a corporate empire on LF, so they might as well pay the workers a good wage. There's no shame in that.

April 1, 2004

It's frequently convenient to express aspect ratios with one on one side. This allows you to draw one frame inside another frame with each width or each height equal to one.

TV = 1.33:1 or 1:0.75

35mm = 1.5 :1 or 1:0.66 (Two original movie frames stuck together)

4x5 = 1.25 or 0.80

(0.8-0.666)/2 = 8.33% lost off each side, not accounting for viewfinder and printing crop factors.

35mm is thus one of the longer standard formats.

April 1, 2004

A stationary magnetic field will attract a ferromagnetic metal such as iron, cobalt, or nickel. Not found in film.

A moving magnetic field will generate currents in any metal, including silver. Faraday's Law.

But undeveloped film contains only silver halide compounds such as silver iodide, bromide, etc. The only metal is in the form of very small groupings of silver atoms on the edges of grains which constitute the latent image. This conversion of silver halide to silver atoms must be caused by a photon, be it a visible or x-ray photon, etc.

It couldn't add dots to the latent image because it could not remotely have an effect on the non-latent-image silver halide grains as they do not conduct.

And magnetic fields have no effect on photons, just electrons.

March 28, 2004

I imagine the layers mentioned earlier are between layers of cellulose acetate. It would be difficult to scrape off all of that.

If you wanted to dissolve each emulsion (no scratching) then mix them and redeposit them as a single layer on film, you'd still probably have a problem with putting the film in a camera. But then I don't know if there is a thin layer of acetate on the emulsion side.

Kodak, especially, prides itself on its T-grain structure. If you were to dissolve the silver halides and precipitate them out again, your grains would probably be larger and much rounder.

Then there's the sensitization step. I don't know how that works, but I think it involves some aging.

The result would bear no relation to the properties of Ilford or Kodak film because the uniqueness is probably in the production techniques, not the composition.

February 20, 2004

Kodak EPH ISO 1600 gives low contrast and low color saturation. A browny cast can be achieved with a filter or two, especially with the added speed.

February 20, 2004

Would it be practical to hyper the film to increase the ISO?

http://www.astropix.com/HTML/I_ASTROP/I09/I09.HTM

February 17, 2004

It's always good to know *what* old wives' tale you're laying to rest. The way I heard it, you use a lead lined bag when putting film in your *checked* luggage, which is scanned much harder. If the machine sees a lead-lined-lump then they'll crank up the juice, rendering your lead-lined bag useless. If you use the thicker lining, they'll just halt the whole process and hand-search it.

Anyway, a lead lined bag isn't needed for carry-on scanners. I've tried taking some rolls through multiple airports; I wish I had the time to find the negs... Unexposed Superia 1600 ended up with two purple blobs on two frames, but that's inconclusive.

February 17, 2004

If you're asking about the optimum pinhole diameter, I've read that there's almost no wrong answer. The optimum pinhole size is a compromise between geometric (ray) and diffraction (wave) optics. According to some scientific paper I found on Google, there are several ways to estimate the right compromise, i.e. quarter-wave resolution or something. All the methods pretty much agree that the quality of a pinhole image is rather insensitive to the aperture size. It's pretty unsatisfying to some of us. The result is that Rayleigh's equation, developed many moons ago, is as good as anything else, and any deviation from that equation works just as well.

February 10, 2004

Make that change two numbers at a time... That keeps the total exposure the same each time.

February 10, 2004

First of all, the EV system is based on factors of two. Doubling the exposure is done by doubling the exposure time or doubling the aperture area. Because relative apertures are calculated from the diameter, a setting of f/5.6 gives twice the exposure of f/8 at the same shutter speed. A=pi*r*r=pi*diam*diam*0.25 and +1/2 stop shutter speed is 2^(1/2) = 1.41 times the previous time.

EV 15 corresponds to the Sunny 16 Rule: 1/ISO, f/16. The sun itself, I have found, is somewhere above 27 because I can't make exposures any shorter. Reflected starlight is around -5 EV.

Here's what I do: write down a table of numbers. Change only one number at a time. I find myself repeating "More light, less light, more light, less light" in my head if I don't have paper handy. Soon you won't need paper most of the time.

(EV) (ISO) (Shutter) (Apert)

15 200 1/250 f/16

15 200 1/500 f/22

14 200 1/500 f/16

14 100 1/250 f/16

(less)100 30 f/5.6

Simply set your camera to ISO 3200 or however high it will go, and convert from there. Look up The Ultimate Exposure Guide online. It provides some great tables and lighting examples. A building illuminated by street lights should be between 0 and 5 EV.

Then adjust for reciprocity failure; film manufacturers make this info available in their technical publications. ISO 100 film shouldn't be too bad. Maybe 1/2 stop for 30 seconds; no big deal.

The great thing about negative color film and reciprocity failure is that your exposure can be almost indefinitely long, and an extra thirty seconds won't even correspond to one stop. When in doubt, keep the shutter open longer.

February 6, 2004

A few years back I tried Delta 3200 in my Lubitel and the results were really grainy. It could have been partly due to poor exposure. It wasn't the tradeoff I was looking for.

The neat thing, however, was that I could set my Lubitel to f/64 (there's no mark but the lever just keeps going) and get almost everything in focus in daylight.

January 24, 2004

"My question is do lens manufacturers incorporate UV filtering into their lens elements"

Yes, they do indeed! Glass blocks UV. There is some transmission at 400nm but the slope of the curve is very steep, so nothing gets through just below 400. Cheap UV filters may be just a piece of glass. There are more expensive ones that might work better than plain glass.

Quartz crystal doesn't block UV. Something about the band gap I suppose.

Sign In

Profiles

Forums

Blogs

Events

Downloads

Gallery

Store

Posts posted by cole_petersburg