jan_brittenson

Tabs are nice if you have a stiff lens, but are also useful for setting the focal distance without actually looking at the lens. It gives a much better feel for the focal position than a rubber ring.

I just ordered a couple of STEERs, with the intention of trying them out on my Mamiya 7's 43 and 80mm lenses. A quick circumference check suggests it might be a good fit. Might possibly also fit the Leica R 19/2.8 II. Now that lens with a focusing tab and a CV 21 viewfinder in the Canon DSLR hotshoe should be quite a sight! Hmm, I wonder what the diameter of the Summicron-R 35 might be? :)

MTF isn't a measurement of resolution, it's a measurement of contrast (sharpness) at a specific resolution, or using multiple measurements to plot contrast as a function of resolution. Generally it's measured at fairly low resolution though, and isn't a good predictor of how the lens behaves at higher resolutions. It also inherently doesn't say anything about _why_ there is a loss of contrast -- such as whether it's due to chromatic aberration or spherical aberration (say). Different aberrations look very different. Also, there are performance criteria that aren't even factored in MTF, such as veiling flare; the slit used to sample the spread function simply doesn't permit sufficient energy through to significantly flare the image. Then there are problems due to actual measurement method used, for instance whether the lens is measured at the exact registration distance (important for floating elements to do their thing), and whether it's adjusted for curvature of the object field at each measurement. There are many more pitfalls beyond this. Basically, MTF only tells you about half of what you need to know about a lens to make an informed decision. And it only tells you this half if you actually read the curves and their relative shapes carefully. If you try to turn this into some sort of score (like photodo does), you've basically thrown away 9/10 of the useful information.

Wow, what a polite and socially pleasant conversation. Where's the fire and brimstone that usually accompanies opinions? :)

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<i>Jan: If I give a roll of EFKE to a commercial lab, what would be most likely their B&W developer?</i><p>

My guess would be XTOL, since Kodak sells and supports it for volume processing and it works well for machine agitation. But I'd ask. Most commercial labs tend to overdevelop for my taste, so you may need to go a few rounds to find times that give you what you're looking for. Make sure they let you specify what time you want. If results look high contrast, reduce time by say 30% and try again.

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Personally I like developing B&W film myself. XTOL and TF-4 fix, just a water rinse for stop and the Ilford water saver technique for wash. A PhotoFlo dunk before hanging. Kind of therapeutic. :)

I wouldn't be so quick to assume the pictures are crap because they look uninteresting on-screen. Keep in mind that paper looks very different, since the brightest white you're going to get is paper white; and this isn't nearly as bright as a screen, especially with fine-art papers without optical brighteners (like say Moab Entrada Natural). What may looks harsh and unappealing on-screen will soften greatly on unbrightened rag and may simply assume a graphic quality and character that's impossible to communicate on-line.

 

Also, scale makes a huge different, those images clearly weren't shot for web viewing since they lack a single, clear, frame-filling subject. (Often the same type of image that looks boring and amateurish in print, with ultraglossy papers and gaudy coloring in an attempt to make paper and ink mimic the screen impression.) One needs to take the intended output medium in mind when evaluating images.

 

I hardly ever post images online anymore for this reason, most readers simply don't have the experience or interest in trying to translate what they see on-screen to what it might look like in print. And the "700-pixel web image" medium simply isn't interesting to me. But places like this are great for "shop talk"!

Efke 25 is a fine film, seemingly able to produce worthwhile results no matter what developer you use. I've tried it with FX-39, Rodinal, Ilfosol-S, Microdol-X, and XTOL, and it works equally well with all of those. I currently use it with XTOL, mainly because I also shoot TMX, Delta400, and Maco 820c, and all of those really shine in stock XTOL.

 

I agree on the Mamiya 7 though. The perfect weight/quality compromise for static subjects! :)

I think any brassing should be disclosed, and always ask if there is any unless the seller clearly stated there isn't. That's why asking for pictures is useful. I'd be a little peeved if the seller didn't disclose it, but I doubt I'd post here about it. I'd be peeved not because I wouldn't buy the lens, but because the lens is worth a little less than I thought (maybe $25 or so), which I will lose if I resell. I'd also be peeved if someone stole $25 from me under different circumstances, not so much at losing a small amount of money as at the cheapness of some people.

 

The Mamiya 7 shades can be a PITA to mount in a hurry, but seem less prone to stripping than one might think.

To me the M6's .72 VF is perfect for a 35mm lens, but you might wish to consider the .58 if you shoot with glasses on. The M6 is good with the Nokt 40, although I modified mine to bring up the 35mm framelines. The lines are somewhat conservative, so will make a pretty good match for a 40 lens.

Hopefully it's the cell that needs replacement and not the VA part! Have you tried cleaning the cell, perhaps it's just foggy with dust?

<i>Frank, it's worse than you think. I've just checked my lenses and they all seem to use some kind of derivative of sand for the optical elements.</i><p>

Not only that, but it's not even all glass but it's full of air! Only something like half is actual glass, the other half is air! Would you believe it? Not even exotic gasses, just plain old cheap air! Makes me angry just thinking about it. >(

<i>The dynamic range would be identical to that with the color filter array since the filter array does not affect either of those parameters.</i><p>

This is true for white light. For anything else, the color filtering increases dynamic range as measured in SBR at the cost of sensitivity. If you think about it, an SBR of ten stops in red will saturate the red sites but not green and certainly not blue. As a result, red brightness levels beyond the saturation point of red can be differentiated through the relative levels of the two other channels. The more spectrally narrow the light, the higher the dynamic range.

Couldn't you just strip the color filters off an existing camera?

I wrote "On the ground we get on average (USA) 0.27mSv from radon alpha, at 30kft that's replaced with 0.27mSv cosmic X-rays". By this I meant that .27mSv of radon alpha is relatively harmless compared to .27mSv of cosmic X-ray. Yet purely by the numbers there wouldn't seem to be any difference.

I'm not asking whether there's risk, whether in anyone's opinion it's high or low, or whether it's higher or lower than something else -- but exactly what's emitted and how much so I can make my own decisions. What's pretty clear from reading the stuff I could find is that none of the information is designed for a person to make a health risk assessment. For instance, X-rays are 2-3X as mutagenic as gamma, which is many orders of magnitude more mutagenic than alpha even if the latter is in the form of inhaled gas. Yet there is only a single measurement (usually expressed in mSv, millisievert, or sometimes cSv) for dosage. Doesn't matter what kind of radiation it is. Similarly, the MPD set by the government is 1mSv annually for non-radiation workers. (I suspect that's actually 1cSv, or 10mSv.) But 1mSv of X-ray is mutagenically comparable to 2-3mSv of gamma, or maybe several Sv of alpha. (Several Sv of X-ray would kill a human within seconds.) Not only that, but the effects are completely different -- a whole Sv of alpha would more likely cause severe surface burns, not internal organ failure (other than indirectly). The exception is alpha in the lungs, but even that is far less mutagenic than even gamma by several orders of magnitude.

 

Yet e.g. the air industry applies the same 10mSv MPD limit. On the ground we get on average (USA) 0.27mSv from radon alpha, at 30kft that's replaced with 0.27mSv cosmic X-rays. Over the pole on a transatlantic flight it's 3X that. It doesn't take a genius to recognize that the health risk isn't comparable just because the dosage numbers are the same. One site mentioned a limited study that showed airline pilots, despite being generally healthier and less prone to cancers than normal, have 4-5X as many cases of certain forms of Leukemia, 2X certain brain cancer, and various other illnesses typically contracted from radiation exposure. Curiously, this was hypothesized by one writer as not caused by cosmic radiation but radar (i.e. microwave).

 

A chest CT scan on an adult was listed by one document as 5mSv. A head area (e.g. dental) X-ray as 1.5mSv. These are X-rays, not gamma, and positively not alpha which wouldn't even work. With 2-3 images made each time, that's equivalent to 400 and 100 hrs of flying, respectively. A 75000 mi annual frequent flyer flies about 250 hours, and a commercial pilot about 1000 hours. Clearly one can't just say a dental X-ray is equivalent to flying unless we're talking about airline pilots.

 

I also don't think cosmic radiation or a lens element, or some such is a strong enough X-ray/gamma source to fog film.

 

It's also not reasonable to say a risk should be ignored because it's lesser than something else; the sum is always greater and risks additive, sometime they grow geometrically (when multivariate). Also, when assessing risk the probability needs to be multiplied by impact and these negative expectancies accumulated.

 

I think it would be far more useful if radiation dosage were measured in terms of "mutagenic power" rather than the number of decay events or some such. (The latter has clearly its uses, but doesn't seem to me to be directly related to health effects.)

 

Anyway, it seems to be a difficult area to assess, and apart from the juvenile penis jokes isn't one many like to talk about.

E160T works very well for this kind of stuff, personally I find it's just perfect with a KB3 filter. E200 Pro with a KB12 can work well too.

 

Also, NPS is good (and available in sheet sizes).

I'm not concerned with alpha-beta, but has anyone measured the X-ray

emissions from one of these lenses? I just got a rather yellow one;

it's sitting wrapped in foil on the window sill right now, and I'm

wondering how much it emits at X-ray energy levels. If I understand

correctly it doesn't emit a whole lot of gamma.

 

I read somewhere that it emits the same as a transatlantic flight.

How much is that? Is that mainly cosmic or solar radiation? I

understand solar photonic radiation is mainly at gamma levels while

cosmic radiation is X-ray? (Actually, I don't have a clue what makes

me think that but I'll leave it here anyway.) Is this a nightside or

dayside transatlantic flight it's equal to? At what latitude and time

of year? Route? Direction?

Here's an example of a zero-slap camera, the Mamiya 7. This was shot at 1/2s wide open with an 80mm lens. It's the nightly Brahmin Ganga ceremony in Varanasi, India. If you follow the Sadhu in the foreground, up to the western tourist with a pony tail in front, then up to the Indian tourist woman, you'll notice she has something shiny on her left wrist. That's a watch, and on the film I can read the dials to see when the shot was taken -- that's as far as this lens will go wide open on Ektachrome 200 Pro.<p>

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I don't have the full scan on hand right now, but would be happy to post a crop if anyone cares.<p>

The Canon 1Ds2 simply can't do that; apart from lower resolution, it also couldn't produce a tack sharp image at that speed no matter how it's braced. It has nothing to do with blacking of viewfinders (it was sitting on a concrete wall, and I wasn't even looking through it). A heavily weighted tripod could help the clunky Canon, but why bother when there are cameras that don't need it to begin with! Of course, MLU fixes it on the Canon which just further proves its lack of proper counterbalancing on the mirror lift.

Andrew, what does your handheld shots look like enlarged to 16x20? That's my normal print size. The images you posted look like they're 3x5 or so on a 100 dpi screen, obviously that size is very forgiving.

If it were B&W done yourself I would have guessed inadequate developer volume. But since it's color, presumably done by a roller type processor, the most likely explanation is errors in curtain timing. Verify it on another roll; if it persists get the shutter looked at. (It's probably way off on exposure, as well.)

My experience is that body weight is a very poor predictor of the effect of mirror slap. My Canon 1Ds2 for instance, is unusable without MLU at 1/4-1/15s with a 300-600 range telephoto, but also shows slight softening even with wide angles at those speeds. Every telephoto image shot will be double imaged in exactly the same way. Lock up the mirror and they're just like you'd expect. Compare this to the R9 where I personally have never been able to detect any benefit whatsoever of locking up the mirror. IMO it simply doesn't need MLU, and I never use it. (Ironically, the Canon which really needs it requires deep diving into custom functions to turn it on, while the R9 has an easy to use switch on the front.) Because the Canon sometimes needs it I tend to use it whenever I can, merely to err on the side of caution. I do most of my shooting with the Leica 19, and sometimes in low light where I shoot at 1/8 or 1/15 handheld stick a C/V 21 finder on it and shoot with MLU enabled. The Canon of course weighs more than twice as much as the R9. It's really a pig to work with since not only is it a huge, heavy monstrosity, but also needs an equally heavy monstrous tripod to block the slap. Not particularily well engineered at all.

Looks like bad bleach/fix that has left stains.

<i>Can those angels be cleaned out during a routine CLA? What are you saying?</i><p>

I think poor Harry says his head hurts from all the thinking, and that he doesn't like intellectuls.

<i>And when you say that a flat surface has an effect, are you saying that a flat surface can correct abberations? Seems to me they make filters as flat as possible to prevent them from having any optical effect.</i><p>

A flat surface is not an optical no-op. It's a refractive boundary still, and so its effect depends on the glass used and the angle of incidence.

Nothing like wildlife with nowhere to go! All with APO 280/4, some

with APO 1.4x, some with APO 2x. On a Canon 1Ds2.

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<br><i>Bad hairday!!!</i>

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<br><i>Can you spot the Hippo?</i>

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<br><i>Warthogs are cool</i>

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src="http://www.rockgarden.net/download/SFzoo2/VI0W6345-06445-700.jpg">

<br><i>Black (and White) Rhino</i>

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<br><i>A cat is a cat</i>

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<br><i>Can it get more canonical?</i>

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<br><i>Dude, take a chill pill!</i>

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<br><i>North American River otter exhibit</i>

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<br><i>Alright, a Zookeeper with a hose!!!</i>

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<i>Once you have a settings as a Profile</i>

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I meant to say, once you have settings that work, save them as a Profile...

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If you're concerned about Dmax, do this: take a piece of opaque film (or create it by throwing a sheet in a tray of developer in daylight, then fix and rinse it) and write something on it with a sharpie. Put it in the scanner. You should have no difficulty seeing what you wrote on it in the preview. If you want to know where in the histogram "black" falls, stick a piece of gaffer tape on the film.