Page 7 of 22 FirstFirst ... 5678917 ... LastLast
Results 61 to 70 of 214

Thread: f64

  1. #61
    A.K.A Lucky Bloke ;-)
    Join Date
    Jan 2008
    Location
    Newton, MA, USA
    Posts
    637

    Re: f64

    Quote Originally Posted by Kirk Gittings View Post
    What is the chemical mechanism where one gets more pronounced grain (and what appears to be sharper grain in the Xtol example) AND less sharpness in the DETAILS of the letter image? This seems counter intuitive me.
    Kirk, the grain in the xtol is not sharper, just bigger. It's sharper look in this post is a product of down sampling/grain size/ scanning resolution being close to multiple of each other.

    I'm trying not to get in the subject but I think the big difference here is stain vs not stain. The scattered light in the Nikon sort of amplifies the effect. IMO, the stain reduces a lot of the dispersion and diffraction occurring around the “clean” grain and reaching the neighbor cells in the CCD.
    Armando

  2. #62

    Join Date
    Sep 2003
    Location
    Massachusetts USA
    Posts
    7,833

    Re: f64

    Are the stain molecules, simply smaller than film grain clumps ?

  3. #63
    A.K.A Lucky Bloke ;-)
    Join Date
    Jan 2008
    Location
    Newton, MA, USA
    Posts
    637

    Re: f64

    Quote Originally Posted by Ken Lee View Post
    Are the stain molecules, simply smaller than film grain clumps ?
    That's a good question. I don't believe the stain is in any form of clumps like the silver but if it is I'm sure is at least a hundred times smaller, enough to ignore it.

  4. #64

    Join Date
    Sep 2003
    Location
    Massachusetts USA
    Posts
    7,833

    Re: f64

    In his article Pyro Staining Developers on the Unblinking Eye web site, Sandy King quotes Steve Simmons as follows (bold emphasis mine):

    “In other words, there is no general overall stain that would act like fog, but a stain that acts like extra density and this stain increases as it goes up the tonal scale. Consequently, the film’s high value silver densities are thinner than with a conventional developer, and the extra density needed to produce the high value tones is created by stain. These ‘thinner’ high value densities in the negative can produce wonderfully clear delicate high values in the print, unlike any tone that can be produced by a non pyro film developer.”

    He goes on to state the following:

    "Highlight separation, sharpness and acutance are increased because Pyro gives more pronounced edge effects than other developers. This is due to the fact that there is very little migration of silver halide during development, resulting in a more precise reduction, which enhances sharpness, and because Pyro tans and hardens the gelatin during development, thereby reducing the effects of irradiation (scattering of light in the film emulsion) and infectious development (spreading of silver development beyond the exact image boundaries)."

  5. #65
    A.K.A Lucky Bloke ;-)
    Join Date
    Jan 2008
    Location
    Newton, MA, USA
    Posts
    637

    Re: f64

    The grain is almost invisible in the near white tones. In fact, I usually extend the development knowing the stain will be higher and then recover the gamma in PS.
    Sometimes the edge effects are associated with stand development but both films were processed in a jobo at full speed. Also a 3rd one developed in 510-pyro is very similar to the one in Pyrocat-HD.

  6. #66
    falth j
    Join Date
    May 2006
    Location
    Above the Straits
    Posts
    145

    Re: f64

    “wmokrynski” in another post titled:

    "Focus" problem that is driving me insane”,

    seems to be having trouble with differing focus and out of focus areas on his negatives, and cannot understand the cause...

    some posters are saying negative pop,

    yet other posters are intimating that ‘diffraction’ lens opening size is always something one must always consider in the issue of overall image sharpness…


    What I’m reading in this post f64, Lenny seems to be saying that for himself, he has not found this to be the case…

    and et al…

    is that diffraction, size of lens opening are not of importance, in the issue of image sharpness,

    while other indications imply that lens design and diffraction are least when the lens is wide-open…

    see the article in Luminous Landscape on Diffraction:

    www.luminous-landscape.com/tu...fraction.shtml


    Much to digest and apparently I am seeing two differing points of view, or two different area of concern/problems ?

  7. #67

    Join Date
    Oct 2005
    Location
    Petaluma, CA
    Posts
    2,089

    Re: f64

    Quote Originally Posted by Kirk Gittings View Post
    What is the chemical mechanism where one gets more pronounced grain (and what appears to be sharper grain in the Xtol example) AND less sharpness in the DETAILS of the letter image? This seems counter intuitive me.
    I'll try and explain this succinctly, I'm sure others here could do better....

    This all has to do with the right balance. I appreciate the example being posted, however, I generally re-check everything done in 35mm, as it seems to be different film, perhaps the same formulation, but thinner emulsions, and there are plenty of other factors I am sure I am not aware of..

    Developers are primarily a developing agent, and a degree of alkalinity. (Usually.) The more alkaline, the more active the developer will be. Then there's the wash of clearing mechanisms, in the old days this was usually sodium sulfite. Then there's a few techniques, two bath development, multiple developer iterations, agitation strategies, roller base vs trays and a bunch of other things that affect the overall result.

    The two main families of developing agents are Metol and Phenidone. There are others, Hydroquinone, Pyro, Glycin and a bunch more. Last I looked, Xtol is based upon Phenidone, altho' it is some variant thereof.... Metol development is what we are used to in things like D-23 and D-76. Phenidone has the action of coating the edges of the grains with dark, which often outlines the grains. Take a look at the etched grains of development like Rodinal, for example. If this effect is limited, Phenidone can be a terrific developer.

    The one difference that short-circuits my general understanding is that Xtol is not based upon an alkaline activity controller, but uses the opposite, specifically ascorbic acid. (Maybe from orange juice! Go figure.)

    When looking at onnect17's example, a couple of things that come to mind. Mainly, his Xtol was simply more active than the Pyro. This means that it went thru like a roto-rooter. It washed out silver between the grains. It also did not articulate the darker areas as well. That's very interesting. We tested many developers against Xtol, altho' we left Pyro out of our testing, and Xtol won every contest - in our darkroom. That last comment - in our darkroom - is important...

    If the strength of the Xtol was matched exactly to the Pyro, would it be closer? Maybe, but probably not. One might imagine so if you looked at the dark letter and imagined that it was bleeding, but the truth is the other letters are lighter and it doesn't look like that.

    Pyrocat is a fairly weak developer in most formulations. It also doesn't etch the edges of the grains like Phenidone does. There is probably a difference in the agitation, or in the way the developer-film combo responds to additional agitation.

    I'm not ready to say that Pyro is simply sharper. Not until I test it for myself... But it might be.. and there are other benefits. It's important to me to be able to develop a number of sheets at a time, as in a Jobo, and not use development times like 22 minutes, if it can be avoided. That has to do with my shooting style... and what I think I need.

    I acknowledge onnect17 for doing his own testing. Personally, I won't ever use 35mm for anything. The Mamiya 7 is small enough to carry around as if it were a 35 and you get a decent-sized piece of film. That's a very personal choice, of course. But it also colors what I will see in the printing. My last test was about finding the edges. I'm almost complete.....

    I hope this helps and, even more, I hope its what you were asking...

    Lenny

  8. #68
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    10,602

    Re: f64

    Faith - all of the above are real factors. Anyone who thinks they are just differences of
    opinion is full of *%@#! Plus this discussion has entered into a whole other arena of
    digital factors which are not directly lens related, but to how the film data translates
    via workflow, and how to simulate a sharp image rather than check for actual lens performance in the first place. And now apparent grain effect vs actual, which often depend on the mode of printing etc. One needs to study these issues one at a time to
    get ahold of them, rather than lumping together a cumulative sum and guessing what
    is happening. I should probably just shut up because I don't dovetail with the geek
    mentality very well.

  9. #69
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    10,602

    Re: f64

    Ken - since the different pyro developers have somewhat different effects in relation to the color of exposure light, what I sometimes do in cases of a developer new to me
    is to view the magnified image through a deep tricolor filter. This gives an approximation of how things will look to the printing medium itself, relative to its own
    sensitivity, of course. I find it interesting that my precision Peak easel magnifier came
    with a deep blue accessory filter as standard equipment, back when most papers were
    just blue-sensitive. But it comes in handy sometimes now for evaluating the effect of
    pyro stain on extremely fine detail - more an issue with smaller formats where the film
    grain is actually apparent. With variable-contrast papers there are significant differences between the kinds of stains produced by the yellow-green of PMK, for
    example, and some of Sandy's pyrocat formulas, and the W2D2 approach. I imagine
    this would have a significant effect in scanning for a single color channel too, which
    some folks do if order to read through the stain.

  10. #70

    Join Date
    Sep 2003
    Location
    Massachusetts USA
    Posts
    7,833

    Re: f64

    "Pyrocat is a fairly weak developer in most formulations. It also doesn't etch the edges of the grains like Phenidone does".

    Perhaps you were referring to Pyrocatechin alone.

    Pyrocat HD contains Phenidone. See http://unblinkingeye.com/Articles/Pyrocat/pyrocat.html

Similar Threads

  1. my experiance w/ f64 backpack
    By Steve M Hostetter in forum Gear
    Replies: 21
    Last Post: 31-Jan-2009, 08:50
  2. Feedback On the f64 Backpacks
    By paul owen in forum Gear
    Replies: 9
    Last Post: 30-Jan-2004, 13:18
  3. Shooting all the time at f64
    By Raven Garrow in forum Style & Technique
    Replies: 9
    Last Post: 24-May-2000, 20:25

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •