dave_t

<i> ... the best when it comes to great quality and wide range of possibilities when it comes to photography.</i>

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Lots of high quality kit out there from many manufacturers. As far as "wide range of possibilities", well, that's the job of the picture taker. And unless you need something (a lens, a flash unit, whatever) that one mfr makes but another doesn't, then it really doesn't matter. They're all good enough that the name on the camera is not going to be the limiting factor. So get whatever you like better, use it to death, and don't waste time second-guessing.

 

Re: 20D. Excellent camera, but you have to tell us what you want to do with it. If you're looking for something with interchangeable lenses and a comprehensive system, it's great bang for the buck. If you're looking for a lightweight camera to take everywhere and fits in any pocket, it's a waste of $1000. What do want to do with it? (If you're looking for a pocketable P&S, try the Fuji F30.)

The reason yellow is traditional for BW is that BW films are more sensitive to blue light than to red, and the yellow filter was intended to get the final spectral response more like what we see. This was more of an issue with earlier films, which were more orthochromatic than current films. In the end, use what you see fit, and don't worry about what you're supposed to use.

Jim Gifford wrote:

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<i>I believe there is an error in the definitions... the concept of "frequency" is not easily translated to the concept of "resolution" for purposes of making the aliasing theory hold here.</i>

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Actually it does, if frequency refers to spatial frequency. Wavenumber and position are, of course, Fourier transform conjugates. But I do agree that the original objections are bogus.

Not even close. Wonder what the guy's response would be if Mamiya made LF cameras ...

<i>Have you guys ever actually done this? You're certainly struttin your bad tech self...except it's not all that hard.</i>

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My, my, touchy, aren't we! Yes I have done this, though not for photographic purposes (weird lab experiment -- technically more demanding, fortunately no call on artistic talent), and no, it's not that hard. The point of my post was to clarify terminology used in error (especially as Edward Ingold clearly knew better) and to point out that Brewster's angle is not actually a fixed magic angle (though it's pretty close)

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To the original poster: you seem to favor shorter focal lengths for this type of work. What's the reasoning behind this? Lens availability? Working space? A bit long of normal (180-210 in 4x5, 100-120 in MF) would reduce falloff and perspective issues.

<i>Light reflected from a dielectric surface (e.g., a painting) is partially polarized in a plane parallel to that surface. The angle of incidence for maximum polarization is approximately 37 degrees (close enough to 45 degrees).</i>

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Methinks you need to define angle of incidence. Most people I know go from the normal (not that it matters if you pick 45 deg....) And if you want to get really picky, that 37 deg (I'd call it 53) is really for water whereas what you really need depends on the index of your substrate.

<i>A circular polarizer will cut down on glare and any reflections off of water.</i>

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So will a linear polarizer, and will be even more effective and less expensive. RF's aren't a natural at this but with a little care you can get the angle right. Just remember that the filter factor is variable with a polarizer (but hey, FP4+ is pretty forgiving).

Pan F+ is excellent in both XTOL and Rodinal. Actually, it's great in just about anything. Ilfosol S is a high energy odd duck with a short life span. But it's simply brilliant with Pan F+, perhaps the film it's really made for. Lovely combination. Use it at 1:14, ignore the "economy" label. It maybe slightly more grainy at that dilution (not that you'd notice with this film), should in principle be slightly sharper (not that you'd notice with this film), definitely more consistent than at 1:9.

<i>Will there come a time in near future when B+W film is no longer made?</i>

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Maybe, but right now you can get more emulsions in more different sizes than you could 5-10 years ago.

Contrast in the neg is controlled by development. It helps to think through all the way from exposure to printing. But if you want a film with inherently low base fog and is fabulous for portraits, try Pan F+. Might be slow for street use ...

Was out by the river with the baby Tech, a guy asked if I was done shooting video so he could pass (without getting in the picture). The statement did not compute as the camera is about 45 yrs old so I looked at him blankly. Hours later I realized he must have confused the GG for an LCD screen.

The 200M is f/8, which is not a big deal for me but may be for you. Also a Tessar, IIRC. At f/22 and smaller, I'd guess that the Geronar is as sharp as anything else unless you use a lot of movements (I don't have the Geronar so I can't verify that). If you don't mind old, and a bit slow, consider the 203/7.7 Ektar, yet another Tessar, also single coated. Small, sharp, cheap.

 

You don't specify a format -- if you ever go larger than 4x5 you might also consider the 210 G-Claron (it's f/9, again not a big deal for me but ...) Not quite as small as the 200M or Geronar, but smaller than the 5.6 plasmats, and easier to find than the other wide field 210s.

In the event that you're interested in and are willing to learn about the physical aspects of light (as opposed to photographic, which encompasses primarily artistic and documentary aspects) let me suggest someday sitting down with a good optics book. Hecht and Zajac's <i>Optics</i> is an excellent introduction and recommended for any photographer interested in the physics of light. If you're interested in something more advanced than H&Z just ask, I've got a whole stack.

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Re: diffraction limited images: all it takes is a little <a href=http://www.pinhole.org/gallery/index.cfm> looking </a> <a href=http://hubblesite.org> around</a>.

<i>Please tell me how a ray of light knows which of the different and supposedly competing or conflicting laws of geometry you want it to obey or disobey at any one time? I've asked this before but no one has yet to offer a theory of a super-light-speed inter-communications between waves/rays/photos of light.</i>

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You're making this more complicated than it really is. Some terminology first -- not to get into semantics, but I don't know what you mean by "ray". Photons and waves are both well defined, but you have to be careful about usage because there is a crucial difference, namely that waves are at field (as in "light is an oscillatory electromagnetic field") level and photons at energy (field^2) level, so that in the photon description phase information is lost - you can kludge it back in, but for interference effects such as diffraction working at field level is much more natural. You seem to be describing light as a stream of photons, which is fine if you keep the above in mind. Otherwise you'll have to work mighty hard to understand interference. Think about light also as a wave and not only does interference naturally follow, but so will the dependence on geometry (aka "boundary conditions")

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<i>I put it to you that each individual ray of light does not know nor care about anything except that it alone as hit an edge and diffracts accordingly.

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Our observations are of the collective effect through a lens and (a roughly circular) aperture, and I am postulating that our observation criteria do not in the least concern any individual wave/ray/photon of light on it's trajectory, whose individual path is ignorant of the paths of other waves/rays/photons. </i>

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No offense but I don't think you believe that. Not unless you don't believe in interference. Not unless you don't believe in refraction. And you still haven't explained <i>why</i> it is that light diffracts at an edge.

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Re: actual results from real lenses. I submit that for the vast majority of photographic work (high resolution 2-D imaging such as copy work and astrophotography excepted) such results are just as irrelevant as theory. How many times do we have to stop down for DOF, how many of us use heavy camera stands (or even beefy tripods), how many of us put a loupe on the ground glass for critical focusing, how many of us use the biggest format we can carry (since if we're talking ultimate sharpness we clearly don't care about DOF)? And ultimately, photography is about vision, not replication, and diffraction limited performance is important only to the extent that that helps express a vision. After all, some of the strongest visual images were done using a paintbrush and palette knife.

I think you're on the right track. Think of accutance as amplitude of MTF, resolution as length. It's easier to alter the amplitude by digital postprocessing, within limits, as length is fixed. (I prefer the wet darkroom for BW but digital for color)

<i>Diffraction is where light bends when going over an edge.</i>

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Your reasoning is right for some geometries (such as a linear obstruction) but not all (like an aperture). To see why geometry matters, it helps to think about why "light bends when going over an edge." There are a couple ways to do this, probably most people would use <a href=http://www.mathpages.com/home/kmath242/kmath242.htm> Huygen's wavelets </a>, where destructive interference through a small aperture is less complete than through a larger one (and is only truly complete through an aperture of infinite size), generating greater spreading and stronger fringes -- what we would call more diffraction. <i>Why</i> the Huygen-Fresnel priciple works is an open question ("where do little wavelets come from, mommy?") but it does work, and work quantitatively.

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Another way to look at it is to step back and ask what you're trying to do. A perfect imaging system would render a point in the object plane as a point in the image plane. To get that point (a spatial delta function) in the image plane you need a transverse field with a white wavenumber spectrum. Any obstruction (such as finite size) means that you cannot reconstruct a point in the image plane, and the smaller the aperture the worse the reconstruction -- we'd call that more diffraction. The actual pattern of the diffraction can be varied by changing the wavenumber spectrum (beyond the crude clipping of a window, that is, the <a href=http://mathworld.wolfram.com/ApodizationFunction.html> "apodization" </a> mentioned by Alex Lofquist) but you cannot eliminate the diffraction itself.

<i>The more edge, as there is in a large aperture, the more diffraction. The less edge, as there is in smaller apertures, the less diffraction.</i>

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Eh? Where does this come from? Alan Davenport is right: for circular apertures (or any hole) the diameter is what's important.

Not entirely sure what the question is (I have an old Arcteryx Bora 80? -- something like that. If you go out >1 week, or in winter it'll be too small) but I find that the <a href=http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=16068&is=REG&addedTroughType=categoryNavigation> Domke 4 compartment insert</a> such as comes with the F2 or F6 is real handy for carrying 3 compact lenses + meter. Well, maybe not the Pentax meter. Much more convenient than wraps, though I could wish the bottom were padded (easy enough to add a bit of foam in each compartment, though) -- at least for Technika/Tachi/Wista/Shen Hao size boards. Just be careful not to upend the thing or everything will fall out. If your Galvin takes Sinar size boards or you just have to have your 90 SA-XL or 300/5.6 you might be stuck with wraps. For the film holders, the elegant way is a <a href=http://www.gnassgear.com/products/product_info.cfm> folding file </a> from Gnass Gear (they also have a very slick lens case, but I already had the Domke ...) -- hangs on your tripod, which is very handy if it's wet out or you're in a swamp, kinda spendy. The cheap and almost as easy way is an insulated lunch bag, about $7 from Target. I think I managed to jam 8 holders in one, although 6 is more comfortable. A film box or two, an empty film box or two, a dark cloth and you're set.

The 7 uses a fiddly kit which takes standard 35mm film cartridges. Conceivably useful if only 135 film is available, or your favorite emulsion is only available in 135. The 6MF uses a <b>M</b>ulti<b>F</b>ormat mask to convert 6x6 to 645 -- horizontally. You still only get 12/24 frames per 120/220 roll, but you lose cropping flexibility. If the MF mask has any utility at all I'd like to know as well. (But the rest of the camera is fabulous!)

<i>But I like the idea someone had about using a smaller view camera with a 120 back. In addition to the Century Graphic, what camera would be inexpensive yet still offer a lot of movement (swing/tilt/shift) and a 120 back?</i>

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Not all that many. There are the Galvin 2x3 and the Gowland 2x3, both monorails, both light, pretty cheap. On the spendy side are Linhofs (TK23, M679), Sinars (P3), Arca (6x9, but modular), and Ebony (various 23s). Or you could get a 4x5 and a roll film back ... lots of options there, though wideangle could be tricky.

Oops, take back what I said about the Hartblei -- wrong Pentax.

I do this fairly frequently (though not at 16x20), works anywhere from great to mediocre, depending on subject and amount of correction (as someone else mentioned, it won't emulate back tilt/swing, if that's what you mean by perspective control). I suspect at 16x20 you'll need the right subject to get really good results -- it won't compare to proper LF but you seem to accept that already. If you have a fair bit of detail, or you need significant correction, well, don't expect miracles. Interpolation is data fabrication and that's obviously never as good as having the real stuff in the first place. I've heard mostly pretty good things about the Hartblei, but even if it's not as good as Pentax glass, it's probably still a better general solution than software correction (saves time, too).

 

If by software PC you mean Photoshop, then yes, just make sure you've got the RAM (16x20 is big) and something to print it with.

The G-Clarons you mention are also excellent lenses (I've the 270). The 240 at 330g is a bit larger than the Fuji A, quite a bit smaller than the CMW, and takes a 52mm filter. Single coated, no longer in production, but sharp, light, has generous coverage and often reasonably priced. Something to think about.

Errm, Troy: it may be 7" to the rear nodal point, but if he gets the focus of an object at ~infinity to be 4" from the flange the 180 Sekor is likely to be a telephoto -- either that or Scott Ricketts really goofed in measuring. I suspect the telephoto (Leonard Evens has it right in his second sentence.)

1) Is the distance from the lens to the object fixed? Try this: image a nearby light source (like a flashlight or desk lamp). Move the closer to and farther from the light source. What does the image plane do as you do this? Think about it, then check out <a href = http://www.mellesgriot.com/products/optics/fo_2_5.htm>this tutorial</a>

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2) Yep, in that order. BTW: how far away are the object and image planes when the image is the size of the object (1:1 macro?)

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3) Yes, but it may not be noticeable. Most noticeable wide open and with wide angle of view lenses.