n_dhananjay3

The composition of the developer typically is based on the intentions

of the designer i.e., what kind of trade-off one is trying to make.

Compare, for example, two metol based developers - D23 and FX1. The

developers are designed for quite different effects and the tradeoffs

required are different. D23 is designed as a fine grain developer and

uses sulfite as a silver solvent - the solvency is key to achieving

the fine grain. For sulphite to act as a silver solvent, it needs to

be present in fairly large amounts (I believe you need at least

50gms/litre to start noting solvency effects). D23 contins 100 gms of

sulphite. Solvency is also affected by the length of time the film

stays in contact with the solvent. Therefore, to balance the formula

i.e., have the film in for some optimum window of time, one needs to

adjust either the amount of developing agent or the alkali. D23 uses

sulfite itself as the alkali (and the virtue of D23 is its simlicity

and preservation - in fact, Henn formulated D23 as a simpler, more

reliable alternative to D76). In other words, other characteristics

desired in the developer dictate the decision of no other alkali.

This leads to the requirement of a fairly high amount (7.5 gms) of

the developing agent, metol.

 

<p>

 

In comparison, FX1 is also a metol based developer but was explicitly

formulated to provide the maximum adjacency effects possible. The

mechanism that is utilized for this is the controlled exhaustion of

the developing agent. This is achieved by having a small amount of

the developing agent, a small amount of sulfite and using an alkali

to accelerate the rate of development. It is worth pointing out here

that different formulae use different methods to achieve adjacency

effects. For example, HDD uses larger amounts of the developing agent

(2gms/L) while reducing sulphite (1gm/L) to provide controlled

exhaustion by reducing sulphites protective action, while FX1 uses

lower amount of developing agent and a slightly higher amount of

sulphite to provide the controlled decomposition.

 

<p>

 

In sum, it is the interactions of various components of the developer

that provide the characteristics of that developer. So, things are

more complicated than it appears at first sight - there does not seem

to be an easy way to arrive at optimum levels for all criteria.

However, the flip side of the coin is the increased flexibility one

has in formulating developers.

 

<p>

 

Cheers, DJ.

If what you mean by thin is that the shadows do not have enough

density, that sounds correct. Presumably, you underexposed the film

by rating it at a higher speed. That means the shadows are

underexposed and nothing really helps much here. The highlights are

underexposed too, obviously, but since the density in the highlights

is also proportional to developing time and you developed longer, the

highlights will gain density. Pushing allows you to extract extra

speed out of the emulsion (and may be the only way out in a number of

situations e.g., handholding in low light etc) but it works best when

crucial areas of the picture lie in the midtones and highlights.

Nothing really saves the shadows (short of other techniques like

cooking the film in peroxide fumes etc). The characteristic curve of

a pushed film will have the shadows underexposed and the highlights

overdeveloped i.e., you will be developing the film to a higher gamma

as well which will increase the local contrast in the midtones and

highlights.

Cheers, DJ.

With regard to John's question about solvency effects of sodium

chloride. Yes, sodium chloride is a silver solvent and is used in a

few developers for this purpose. However, I don't believe its going

to affect anything when preseent in the fixer. That's because by the

time film has reached the fixer, image bearing silver halide has been

converted to silver. The remaining unexposed silver halides are to be

removed i.e., fixed. I'm pretty sure sodium chloride does not

influence the silver image. Now, of course, the use in a developer is

a differeent ballgame altogether since the sodium chloride can

dissolve image beearing silver halide beforee they can be acted on

and reduced to silver. Good luck. Cheers, DJ.

Here is a formula for TF3 alkaline film fixer. 800ml of Ammonium

thiosulphate (57-60%), 60gms of sodium sulfite and 5gms of sodium

metaborate. Add water to bring the volumee up to a litre. Dilute 1:4

for a working solution. Cheers, DJ.

Pinakryptol was introduced by Konig and is a family of dyes - the

formulary sells yellow, green and white versions. Green is said to be

the least effective, can cause staining with some MQ developers but

can be used as either a forebath or mixed into the developer. Yellow

is more active in reducing panchromatic sensitivity and more

compatible with MQ developers but can only be used as a forebath as

it is destroyed by sulfite. White is used in the developer.

Pinacryptol is probably preferred to older desensitizers like Scarlet

N, especially for modern emulsions. Olders desensitizers also tend to

stain film. Cheers, DJ.

I've had good results with D23 at 1:3. FX2 (double the accelerator)

worked well also, although I used to get a stain (like pyro only

tending towards the yellow orange). That surprised me since FX2 is

glycin based and supposed to be resistant to staining. Lack a color

densitometer so didn't explore it further and went back to D23.

Cheers, DJ.

Here is what I know about focus shift. Somebody please chime in if

I'm off base on any of this.

 

<p>

 

Focus shift is supposedly caused by uncorrected zonal spherical

aberration of a lens. All lenses suffer from this defect to some

extent but often it is small enough not to be noticeable. Some types

of lenses are particularly prone to it, Dagors and related designs

supposedly being notorious. The idea behind spherical aberration is

that rays passing through the edges of the lens are brought to focus

at a different point than the rays passing close to the center of the

lens.

 

<p>

 

Spherical aberration, in effect, makes the lens have a band of focal

lengths near the design focal length, in other words, an object at a

fixed distance will produce a series of focussed images as the lens

is moved back and forth around the point of apparent best focus. This

last is important - focus shift also depends somewhat on how you

judge focus -we usually focus visually, the eye will judge the point

of best focus mostly as the point of highest contrast.

 

<p>

 

The actual point of focus from the area near the center of the lens

doesn't change, it is just overlayed with out of focus light from

other parts of the lens. If you judge focus mainly by image contrast

the point of best focus will seem to wander as the lens is stopped

down - this is because local contrast will seem to change and also

spherical aberration is being reduced as you stop down. If you look

at the core image to judge focus you may not be aware of focus shift

except as an increase in image contast. This is why some people think

their lenses do not suffer from this effect. Generally, if you see a

halo of light around highlights as the lens is opened up the lens is

likely to have focus shift.

 

<p>

 

So, the point of apparent best focus will seem to change as the lens

is stopped down. Depending on how you interpret maximum sharpness you

may or may not experience as much focus shift as someone else - its

partly an optical illusion. The focus shift of lenses which have it

will be pretty much gone by the time they are stopped down about

three stops from maximum opening. The worst lenses are supposed to be

single elements of convertible lenses.

 

<p>

 

Folks have suggested that the focus shift would tend to be in the

same direction at all stops, depending upon whether the lens was

under corrected or over corrected. To my suggestion about using the

bulb as a subject. As the above indicates, it is perhaps more

correctly described as a way to figure how you judge focus i.e., do

you vary focus as the lens is stopped down or not. Keep in mind that

a lot of sperical aberration is actually eliminated as you stop down.

The bright bulb allows you to actually find 'a point of best focus'

(whatever that means) when you are stopped down. That is, what you

are actually worried about is whether you judge the focus point at a

different place when the lens is wide open for focussing. I would

hesitate to comment on whether the focus shift is the same at all

apertures or not, given the fact that some people seem immune to the

effect in the first place. I would speculate that it should vary

since the sperical aberration is being reduced as you stop down but

there's probably complex relationship based on the contrast inherent

in the subject etc. The exercise will tell you a) whether you should

worry about focus shift and b) if you should worry about, in what

direction and roughly by how much should you worry about it.

 

<p>

 

Sorry to be so long-winded. Cheers, DJ.

A new source of registration equipment - Alistair Inglis, 4987 Dunbar

St., Vancouver, BC, V6NIV4, CANADA. Tel: 604 - 266 0260.

Cheers, DJ.

John, another thought occured to me. It would seem to be the case

that there should be differences as a function of type of developer.

Slow developers are more likely to be limited by the speed at which

they develop the image i.e., any agitation (maybe even just

diffusion) will do the job of supplying enough fresh developer at

development sites since the rate of development would be slow enough

to be the limiting factor - agitation variations should prove less

problematic with these developers. However, agitation may be more

critical with rapid acting developers since the rate of diffusion may

not be fast enough to prevent local exhaustion. Thus, increasing

agitation with these developers should increase the contrast. Sound

logical? Cheers, DJ.

www.photoformulary.com. Cheers, DJ.

With regard to Jim's question, didn't Richard Henry report that he

found continuous agitation did not impair edge effects? That would

seem to suggest that edge effects are primarily due to movement

within the emulsion itself. I haven't seen any corroboration of that

anywhere else though.

 

<p>

 

For what its worth, I did test the effect of dilution and agitation

on Arista 125 in HC110. I found that agitation did change the curve

shape over there - but only a small bit. Using continuous agitation

provided slightly increased contrast in the highlights (Zone VIII and

beyond) but I should emphasize that this was a small difference. I've

got much greater changes in curve shape by using a different

developer (like D23 to provide compensating development). Dilution

did not change the curve shape at all - different dilutions yielded

exactly the same effect as adjusting times. Extreme dilutions

resulted in some loss of speed.

 

<p>

 

Continuous agitation did require an adjustment of time to compensate

but along the order of 35-40%. My times with 10 seconds every minute

were along the order of 6 mins. 6 mins with continuous agitation

provided about the equivalent of an N+2.

 

<p>

 

Cheers, DJ.

 

<p>

 

Cheers, DJ.

You may find this useful.

 

<p>

 

http://www.vanguard.edu/DMcNutt/Photo/PhotographicInterests.html

 

<p>

 

Cheers, DJ.

Condit is out of business. You can buy register pins from Milton

Bregman Mfg in NJ (Tel: 973 - 822 3554. Very helpful folks. The

smallest registration pins are about 1/4" dia. I've been looking for

a source of 1/16" pins and haven't seen them anywhere - I've

improvised around some machine screws for now but would be grateful

for any sources of smaller pins. Cheers, DJ.

That does sound a bit odd. It sounds like you have ended up with some

compensation i.e., a shoulder in the characteristic curve. In my

experience, if anything, continuous agitation in rotary processing

leads to the exact opposite i.e., increase in highlight separation

and a somewhat flatter toe.

 

<p>

 

Re whether you should be concerned, I guess it depends on the kind of

picture. It will provide better local contrast in the shadows and

midtones but flatter local contrast in the highlights. If that seems

appropriate to the pictures you're making, the negatives should be

fine.

 

<p>

 

I'm still intrigued by the compensation you've got with rotary

development. Did you use a pre-soak? DJ

Ed, the Sterry method actually encompasses two methods - contrawise

and speedwise bleaching. Contrawise bleaching does what you suggest

i.e., alter contrast without altering speed, while speedwise

bleaching alters speed without altering contrast. I should add that

this is what I remember from Kachel's article in DCCT - I've never

done any speedwise bleaching myself. Cheers, DJ.

Don't know about Atomal. I remember David Kachel referred to

something about speedwise bleaching (the Sterry method?) as the way

to get a true decrease in speed i.e., without affecting contrast. If

memory serves me right, he talked of a pottasium dichromate and acid

bath being used as a bleach. Let me know if you are interested and

I'll try to dig out the references. I guess an off the shelf approach

would be to develop normally and use a cutting reducer like Farmer's.

Cheers, DJ.

Just to chime in again....

Its hard to make generalizations about tradeoffs between diffraction

and DOF but.... Its worth keeping in mind that this also depends on

the subject itself. Some pictures seem to benefit from the increased

focus in near and distant objects to the extent that the degradation

from diffraction in the main plane of focus can be lived with (or not

noticed since the increased sharpness in other areas seems to

compensate or enlargement ratios are not huge enough to matter).

Other pictures seem to demand the maximum resolution in the plane of

focus, even at the cost of other objects being less sharp.

Diffraction in macro work can be particularly nasty since the

effective stop is even smaller than the marked stop.

 

<p>

 

Its worth keeping diffraction in mind for a couple of reasons. DOF is

something we are worried about on a much more obvious level. However,

since the image on the GG gets dimmer as we stop down, we often do

not see the effects of diffraction readily. Also, we are examining

the out of focus portions of the image and watching them sharpen up

as we stop down - we're not really paying attention to whats

happening at the plane of focus. Again, I'm not suggesting wringing

hands and paralysis by analysis - its just another variable thats

worth keeping in mind since some pictures can be ruined by it.

 

<p>

 

Cheers, DJ.

Proof needs to be much more concrete than instances. In fact, there

is some interesting research in the psychology of judgments

demonstrating that we often use the ease with which instances come to

mind as a basis for judgments. So, for example, if we are asked for

three instances when we behaved assertively (which is pretty easy to

do), we rate ourselves as more assertive. However, if we are asked to

come up with 12 examples of assertive behavior (which is pretty

difficult to do), we rate ourselves as less assertive even though we

came up with more instances of a particular behavior (almost as

though we were saying to ourselves 'Man, that was hard - if it was

that difficult, I guess I'm not a very assertive person). Its often

referred to as the availability heuristic i.e., we often seem to make

judgments based on the ease with which information comes to mind

i.e., is available.

 

<p>

 

I think thats exactly what's happenning here. Coming up with a few

examples of famous photographers who died of Parkinsons (or come to

think of it cancer, leukemia or some ghastly thing or the other) is

pretty easy to do, from which one makes a judgment that there is a

causal link between being a photographer and disease X.

 

<p>

 

Duane raises another excellent point - what is referred to as a

treatment effect. So, it is not sufficient to show that the

percentage of photographers who suffer from Parkinsons is

statistically greater than the average percentage in the population

(although even that bit of evidence doesn't seem to be forthcoming).

One needs to be able to control for the fact that they live longer to

begin with and are therefore, more susceptible to the diseases that

afflict the elderly. More convincing, of course, would be some

triangulating evidence from pathology etc.

 

<p>

 

Again, this is not meant to be a suggestion to drink pyro or make

selenium bongs. There is no doubt that we do use some chemicals that

are hazardous and should be treated with appropriate caution (a

caution that doesn't seem to be exercise with other household

products like bleach, pesticides etc but thats another story).

 

<p>

 

OK, I'll shut up now.... Cheers, DJ.

It is probably fair to say that most lenses are diffraction limited

at f/64. However, note that poor lenses need to be stopped down

further to eliminate various aberrations, while a good lens may need

to be stopped down less. In other words, if DOF requirements permit,

a better lens will allow you to operate at larger apertures, thereby

reducing the effects of diffraction.

 

<p>

 

The resolution at any f stop can be computed using the Airy disk (the

diffraction equivalent of the the circle of confusion) - note that

this is an approximation itself but a pretty close one. Resolution is

given by 1390/f. This is only an approximation since the Airy disk is

the brightest ring but there are larger but dimmer circles that form.

Also, the wavelength of exposing light has an effect - red light will

yield more diffraction and blue will yield less. Using the

approximation though, at f/64, you can resolve approximately 21

lp/mm. So, at f/64, just about any lens should be functional since

the ceiling is set more by diffraction than by inherent lens ability.

 

<p>

 

Diffraction is only a function of f stop. So at a particular f stop,

you will have identical diffraction effects regardless of focal

length. However, longer lenses have lower DOF and that means you

might have to stop down further for DOF requirements which will

increese diffraction effects.

 

<p>

 

Cheers, DJ.

That is nuts!

 

<p>

 

Also, can someone tell me whether the Toyo loupes hold Captain

Marvel's decoder ring or the keey to world peace something - I

routinely see these sell for more than they cost new. I saw one go

for about $80. Where do these people get their money from - haven't

heard anything on the news about a spate of bank robberies.

 

<p>

 

DJ

I should precede this by saying that I do not have any information

about tests between wooden and metal tripods - the idea to contact

Ries is probably a good one.

 

<p>

 

Its my understanding that resonance is more determined by the design

of the overall structure than by material. The simplest example to

demonstrate resonance is to have a column of water whose height you

can adjust. If you hit a tuning fork and hold it over the column of

air above the water, at certain heights you will get resonance. This

proves that even a column of air can provide resonance. If the

dimension that a wave of vibration is travelling along is specific

multiples of the vibration wavelength, it will develop resonance

since reflecting wavelengths will be magnified by incoming

wavelengths. Its the reason armies are told to break step when they

march across bridges etc. The stridency or otherwise of metal versus

wood instruments is more due to the mix of overtones and harmonics -

musical instruments are typically designed in specific shapes to

provide resonance. As Sean points out, the sounding board of a piano

or the box of the hollow body guitar are designed to provide an air

pocket that can pick up the vibrations from the wood and 'amplify'

it. A Dobro guitar, which is made of metal, can have a distinctly

different, somwhat jangly sound since the metal probably vibrates in

different ways and provides a different mix of overtones.

 

<p>

 

This does not mean that wood and metal do not have different

properties in terms of vibration sustenance. Metal may be better at

transmitting or reflecting vibration than wood (especially non

resonant frequencies which are also damaging for our purposes) etc.

However, resonance is not a function of material alone but also of

the overall structure. In fact, I would venture that the design might

have a greater impact than choice of material.

 

<p>

 

In general, vibration (and the perhaps accompanying resonance

amplified vibration) is more of an issue with cameras with moving

parts - slapping mirrors, shutters etc. With view cameras, there are

very few moving parts during exposure. Even the shutter tends to be a

leaf shutter which does not have the jerk and stop of a focal plane

shutter. So, I would guess that the risk of resonant vibrations is

less of an issue. I think the superiority of wooden tripods tends to

come from the fact that they were typically uncompromisingly designed

for one task - to support a large view camera. They tend to be large

and heavy and that's got to count for something. Metal tripods have

typically been designed with more compromises in mind - seductive

appeals of lightness/compactness etc. One could possibly design a

metal version of the wood tripod (something like a studio stand -

good luck carrying that around).

 

<p>

 

Still, all of this is just hypothesizing. Some data from Ries or

some place would be more enlightening. Just my rambling thoughts for

the morning. Cheers, DJ.

The basic idea is that the cone of light emanating from a wide lens

has a pretty steep angle. These rays of light hit the GG and continue

through. Obviously the image is brightest when your eye is placed in

a direct line to the emanating light. So, when you have your eye near

the center of the GG, the center looks very bright while the edges

look less bright (since the light striking the edges is moving

through at an angle and thus will not strike your eye). If you move

your eye now to the edge to intercept these light rays, the center

will look dark since the rays going through the center are not

intercepted by the eye.

 

<p>

 

With a long lens, the angle of the cone is much smaller. The nett

result is that a small movement (or no movement at all) of the head

is enough to intercept the light rays. Also the light rays strike the

GG at less extreme angles as compared to wide angles.

 

<p>

 

I've never used center filters and cannot comment on whether they

would help (although I think they are meant to help with cos^4

falloff etc - so I wouldn't be surprised if they didn't).

 

<p>

 

Obviously the grain of the GG is meant to provide a partial diffusion

surface to form the image on - the tradeoff is that greater diffusion

reduces the hotspot but makes for a dimmer (and grainier) image. In

other words, a fine ground glass will provide a sharp and bright

image but with a pronounced hot spot, while a rough GG will produce a

moree grainy and dim image but with less of a hot spot. Fresnel

lenses are the typical solution, although they are beest optimised

for each lens. The Bosscreen also gets rave reviews from users.

 

<p>

 

Ron Wisner has an interesting discussion of these points in his paper

on fresnel lenses. Its available at www.wisner.com/viewing.

 

<p>

 

Cheers, DJ.

Filters might provide limited local contrast options in b&w given

your description. The shadows are likely to be bluish while the parts

in sun would be grey or green. Something like a minus blue or yellow

filter might help a bit but not much. I take it you don't want to

mess with lighting.

It might be a good idea to take some document film along - something

like Tech Pan. Also, have you considered developing in something like

pyro? Most of the density can come from stain and you might be able

to avoid the grain etc from overdevelopment. Good luck. DJ.

I'm curious about Agfa 8 as well. Ed, Hubl paste, which is a highly

concentrated suspension reputed to have superb keeping propoerties is

another glycin only developer - start with 500 ml of hot water

(130F), add 165 gms of sulphite, 135 gms of glycin and gradually add

625 gms of pottasium carbonate and add water to make a litre.

Suggested recommendations for modern films is 1:35. Anchell and Troop

suggest that with all pure glycin developers, a speed loss of about

one stop can be expected - I was wondering if Patric had noticed this

with the Agfa 8 formulation? Cheers, DJ.

Does anyone have any information regarding this lens? Its a triple convertible (13 1/2", 20 1/2" and 28") from around the turn of the century (not the last one, the one before that). I was wondering if it was related to the Turner Reichs. More to the point, I was wondering about possible shutters I could adapt it into. Its in some gamey 'Unicum' kind of shutter right now. I guess Packards might be an option but I was hoping someone might be able to tell me keep my eyes skinned for a Betax No 4 or something. Cheers, DJ.