p._jeffrey_ungar

<blockquote>

<p><em>Bob Atkins gives a perfect description of why testing like you suggest can be extremely misleading. <a rel="nofollow" href="http://www.bobatkins.com/photography/technical/resolution.html" target="_blank">Aerial image lens testing</a> figures are not accurate and give wildly optimistic resolution numbers.</em></p>

</blockquote>

<p>I'm not saying Bob Atkins is wrong; however, he did pick an MTF level of 1%. At 10% or higher the conclusion would be exactly the opposite. I guess I'll just have to wrinkle my film plane to match the wavefronts, but that belongs to the flatness thread.</p>

<blockquote>

<p>Rob, not sure what you mean by this as power has nothing to do with sync speed. Perhaps I am mis-understanding?</p>

</blockquote>

<P>

Fast full sync speeds are also useful for reducing the ambient light exposure relative to the flash exposure. Think of photographing a group of people in a sunny area outdoors where you want to fill in some harsh shadows with flash. You can either boost the flash output to be a good fraction of the ambient light exposure (hence the need for more flash power), or use a faster shutter speed to reduce the ambient exposure. Higher sync speeds give more flexibility, but I haven't seen a full frame focal plane shutter sync faster than about 1/300, which doesn't get you much more than 1/250 does.

</P>

You need more image, not a finer sampling of a small image; therefore, large format film because it can be made just about

whatever size you need. Better still would be glass plates for flatness. There are many other issues...

I always just move the old spool to the right side, put the film in the left, and pull the backing paper over to what is now the take-up spool.

Generally, I can get the paper leader into the slot on the take-up spool with one hand. Then I just wind on until the arrow on the backing

paper lines up. I also add some tension with a finger on the film side once it gets going to make sure I get a tight enough wind onto the

take-up spool; otherwise it may not be wound tightly enough to prevent fogging the film from the edges after you remove it.

Chris: previous posts have the answer to your questions but to recap with more detail:

One roll lot 0531 002 exp date 2007/07 shot 2005/04 in a Mamiya 7-II and removed within one hour, processed within a

week with TMAX developer 69F 7:30 10sec + 5sec/30sec inversion agitation, plastic reel, Patterson tank, no weird

hexagonal array of spots on negative.

Another roll from same lot shot 2005/05 in same Mamiya 7-II and removed within one hour, processed 2008/08 (stored at

65-78F, low humidity) with D-76 1+1 75F 6:15 10sec+5sec/30sec inversion agitation, Hewes stainless steel reel, in a SS

tank, and there is a weird tight hexagonal array of lighter density spots on the negative, image areas only. Not exactly a

controlled experiment for comparison, but I don't see anything here that should cause a problem like this.

Coincidentally, the pressure plate in the M7-II has a hexagonal array of inward depressions but they are at a much larger

spacing than the lighter density spots on the negatives. The plate also has two big countersunk holes with screws and

there is nothing like that to match on the developed negatives.

I think I and the poster in the old thread encountered some bad samples from a batch of T-MAX. I was curious if anyone

else had encountered this.

No refrigeration, freezing, or thawing. I did look at backing paper and I see absolutely nothing there -- certainly no

patterns. It was sitting under ambient conditions (65-78F, not humid) and processed recently.

Another roll from the same lot shot around the same time but processed then does not show the dots, so something that

happened in the last three years could have exacerbated some underlying weirdness in the emulsion. The hexagonal

lattice is very uniform over the whole image area of every frame; there are no breaks or separate domains or unaffected

image areas. The only places I don't see it is in the film base + fog region, which is very clear, and in the product and

frame number markings.

I still have some film from this lot (0531 002) as well as another purchased at the same time (0531 001). I'll mark it as

probably "weird" so I don't use it for anything critical and I'll make note of what happens.

Look in the out-of-focus background. It is a very regular honeycomb pattern of spots spaced much farther apart than the

apparent grain. I will attach a better sample since it is a bit subtle on this one.

This is a scan of the negative. The pattern is clearly visible in the negative looking with a loupe. It is extremely regular, so

no way is this anything to do with condensation or processing. Film was shot in a Mamiya 7-II and removed within an hour.

It looks just like the problem the original poster had in 2006.<div></div>

This was asked about once before with no resolution on what it was: (<A HREF="http://www.photo.net/black-and-white-photo-film-processing-

forum/00IEqK">old post</A>).

Some film shot ca. 2005 with exp. date 2007/07 (Lot 0531 002) showed a regular pattern of dots. I think this lot probably had some bad

samples, but it was unexpected. Anyone else encounter this?<div></div>

I just processed a roll of T-MAX 100 of the same vintage (shot in mid-2005, exp 07/2007) and see the same very regular

dot pattern on the negative under a loupe. I don't think this has anything to do with the camera or the processing. Unless

waiting *ahem* a while to process it was a problem. I think this is could be a defect with some samples of film from this lot,

although another one from the same lot shot and developed in 2005 did not have the dots. The lot number is 0531 002 (on

the box and imprinted along the film edge).

QG: True, perspective does not technically depend on FOV, which really just sets the size of the screen onto which the scene is

projected. FOV is just about magnification, but since your screen has a size set by the format, it, too, matters, and sets what you

capture and so affects what may more loosely be called the "photographic perspective" in an artistic sense.

My point about referring to images formed by lenses rather than diffractionless pinholes was about how the image looks, including DOF,

shape of the entrance pupil, etc. -- it isn't just geometric perspective and magnification and so under typical circumstances,

format/focal-length matters.

You may now have the last word.

John S.: I have good luck with eBay, but generally I have not spent more than $200, the sellers had close to 100%

feedback, and there were photos of the item from several angles. Overall, if KEH has what you want, I would still go with

them.

Asher: QG is referring strictly to geometric perspective, which is set by location, direction, and view frustum (read field

of view). The image formed by a lens will also show the effects of the apparent depth of field, and that *is* very different

for normal FOV lenses at the same f/# for different formats.

QG: Asher is referring to how the images look as formed by a lens, not an idealized, diffractionless pinhole, but I'm sure

you know this.

"I've always thought they were the same thing, just a different bottle."

Yes, they are the same thing. It was the cut-and-paste of vintage text on to the new label emphasizing items more common 30+ years ago (glass plates, Panatomic-X, and spools of 620 film) that I enjoyed. Perhaps they just updated the copyright on an old label.

I went to pick up some fixer for film yesterday. Last time I needed

this, I purchased Polymax T Fixer concentrate in a silver plastic

quart bottle, but now in this size it appears to be repackaged as

Kodafix solution in a white translucent plastic bottle -- no mystery

there. (It is still called Polymax T when sold in a 1 gal. collapsible

box.)

What caught my attention is the vintage text on the otherwise © 2003

label. On the front it says it is for "Films, Plates, and Papers", and

on the back it gives special fixing times for Panatomic-X and the

fixing capacity as 120 rolls of 620 film or equivalent per gallon.

I had a vaguely warm and fuzzy feeling for hours.