anders_br_the

Daniel,

 

my statement is not wrong, this is what i have been told by a Kodak photographic engineer. He roams this pages too, name is Rowland Mowrey.

 

I had the opportunity to discuss negative film vs positive film with him by mail and here's a small excerpt of it:

 

> Negatives are inherently sharper than slides, are they not?

 

Yes. And have less grain. There are 2 grain patterns in slides. One from the MQ silver and one from the color dyes.

 

 

If you think Dr Mowrey is wrong, I'd be happy to learn why.

Negative film has smaller grain and higher sharpness than positive film. Positive film may appear sharper because it has high contrast and is the final product, not an intermediate like the negative.

 

Positive film cannot be as sharp as negative since the positive has two development steps (first developer and colour developer) which gives you two layers of grain on top of each other.

 

Positive film has been favoured by pros for the reason that printers are very familiar with them, and the photographer don't have to make prints to show the art director, thus saving money.

Andrew, I have the same camera (RB67 PRO-S) as you and use a standard Nikon cable release with mine.

Thanks you all for replying. The lens front is marked Mamiya-sekor C (with green C) f=180mm 1:4,5. It has the aperture and shutter behind the optics which fits well with Neil's description. I don't have a 127 to compare to, but i guess as has benn pointed out that this is a 180 with a shutter/aperture from a different lens.

 

I think I will return it. There is really no way for me to know what the true aperture is. And with such a "repair" it makes me wonder what else may be hidden.

 

I wrote the vendor a mail last night complaining. I think I will await their response before i decide wether to publish their name. I must say i have had only good experince with them before. So i'm a bit surprised and annoyed by this latest aquisition from them.

 

Thanks all for your input. I appreciate it.

I have just bought a second hand Mamiya-Sekor C 180/4,5 lens for my

RB67 pro-s. To my consternation I saw right away there was something

funny with this lens; the aperture scale read a maximum of 3,8, and

minimum aperture was 32! And the flash mode selector between X and M

has a small screw locking it in the X mode. It was rated excellent,

but the other excellent rated lenses I have bought from this vendor

has been in better shape.

 

It is supposed to be 4,5 wide open and 45 minimum as far as I am

informed. Has anyone ever seen this before? Or are some 180's only

f32 minimum?

 

What would you do about this?

R.T. Dowling; the highest resolving film you could get would be a B&W negative. Then a colour negative which will be less sharp than the B&W since in B&W you get the actual exposed silver grains, while in colour negative you get the dye cloud around the actual exposed silver grain as "colour grain". Colour reversal would be the least sharp as the indirect the film will carry two grain patterns due to first developer and colour developer.

 

So I'm pretty sure you're mistaken :-)

I find Cteins Post Exposure to contain much of interest for a colour printer. Although it is not a tutorial on RA4, you will find much basic and advanced colour printing alsong with black&white, but focus is on colour.

Velvia 50 discontinued?

 

There is no mention of that on Fujis page when I looked it up just now, and I see B&H still list it.

 

Mr. Sirman, what is your source of Velvias discontinuance?

Patrick; From your numbers 70mg O2 can be disssolved pr liter water. If all or part of this is consumed in oxidation, more O2 from the air is free to dissolve. This is an equilibrium. The amount of O2 dissolvable pr liter water will merely dicatate the speed of the oxidation, not limit it unlesss one keep the solution in oxygenfree conditions.

Patrick; You probably form esters when you heat the ingredients in the microwave as you do. I say esters because i do not expect a clean reaction (to say the least). Esterification is an equilibrium, hence you cannot get 100% conversion even if you pray. The reaction is as follows:

 

acid + alcohol <-> ester + water

 

If you're able to remove water as it is formed you will drive the equilibrium towards ester, or you remove ester as it is formed. Ester formation is acid catalyzed, typically a small amount of sulphuric acid is added in ester syntheses to make the reaction faster (although it will work without added acid of course, but slower).

 

The alcohol is bisfunctional so you may form the bis-ester, but you will also have the mono ester. Consider also that there are hydroxy groups in the ascorbic acid, namely alpha to the acid that may also cause internal esterification in ascorbic acid. In other words; expect complex mixtures.

 

I would not expect coloured products from the esterification reaction due to lack of conjugation in the resulting molecule. The orange/red colour is due to other by products or decomposed material.

 

Also consider that you would get totally different results if you heat the glycol first, then dissolve your chemicals in the hot solvent compared to chucking all the ingredients in the oven at once. As I said, things happen fast in a microwave oven, and it is a very hot research field among synthetic organic chemists (as I am).

 

You could ally yourself with a chemist with an HPLC to analyze the resulting mixtures from heating with and without all ingredients in the oven. That would give you some hard facts as to what is going on.

 

And remember glycols are rather hygroscopic, so unless the user is familiar with handling or preparing anhydrous solvents, the glycol is bound to contain water.

There is also one issue so far not raised by the chemists here. One do not use equipment intended for preparation of food for any labwork. This is a rule for ones own safety. Cross contamination of food is inevitable. Never mix kitchen equipment with lab equipment (for your own good).

 

Microwave ovens are used in organic synthesis. They effect reactions orders of magnitude faster or make reactions that are not efficient by normal procedures feasible. This is another reason I find it rather less than desirable to heat solutions with chemicals already in there. Things are bound to happen as Gary discovered.

 

Valid points with respect to fire hazard has also been voiced; I second them. A lab fire is not that fun, and if a beaker full of hot glycol with a little blue flame on the top tips over, you have a big fire instantly. I have experienced lab fires, and these should not be scoffed.

 

Safety rules in a lab are not made up for fun or to annoy people not experienced nor knowledgeable in handling chemicals.

 

With regards to sloppy routines regarding keeping food and lab separated. I know of an instance where a trained professional accidentally drank acetonitrile due to misunderstandings and bad routines. The person in question thought it was his cup of water.

 

So I think Zimmermann and Mowrey do indeed raise important concerns that should not be ignored due whatever motives those underestimating the importance of proper routines in handling chemicals.

with your violent heating cycles I expect you have decomposed part of your material giving colour to the solution. I also would be suspicious of the solution as you have probably dissolved a little polystyrene in your stock solution. That would probably apparent when diluting with water as you may see precipitate.

 

For the future, use only heat resistant glass and teflon in contact with your solution. And be more conservative with the heat. Why not try a water bath and heat only as mush as is needed to dissolve the solids?

Shafi; since you prefer to have paper prints, I's say stick to what you're doing right now.

 

I develop and print my own C41 like you do, and I also process my own E6. You can make prints from slides in a darkroom, but it is more involved than normal neg->pos printing. It will also give you a result which will be lower in quality compared to a neg->pos print. Ilfochromes are very expensive in terms of materials, and have inherent limitations. They are way higher in contrast than the materials you're used to, so expect to learn how to make contrast reducing masks. Ilfochromes display colour crossover in the shadows, so to make truly high quality prints you need to learn how to make colour correcting masks too. Sounds complicated? Get a copy of Cteins Post Exposure to learn more about this. Personally I find the Ilfochrome prints extremely sharp and colour saturated, but demanding with respect to colour accuracy and contrast.

 

If you want prints from your slides, my best advice would be to get them scanned.

 

I have made prints on regular RA4 paper from slides, and gotten decent results, but it is more work than using negatives.

 

Negative films are technically superior to slide films with respect to sharpness, grain, colour accuracy, contrast and exposure latitude. Sildes are exellent for projection. That's what I use them for. Remember slides can for technical reasons never be as sharp as negative films due to the fact they undergo two development steps. There's a first developer and a colour developer in the E6 process that will each give each grain pattern on top of each other.

 

I like and use both types of film, but for prints I use negatives.

Develop it yourself. Thats what I do.

Blank out the red LED's.

 

Make sure you don't have contaminated your colour developer with blix.

 

Make sure eventual red safety filter on enlarger is not in the light path.

 

Thats the most obvious pitfalls i can think of from you getting blue prints.

Dave;

 

One little thing that might influence your results. If your atl does not rinse out all bleach and fix properly after you're done with it, that might account for your problems with grain and colour. Just an idea as you say you have residual water in connecting hoses and that density does not suffer, but grain.

 

Never used kodak c41 myself, but have achieved exellent results with two 35mm rolls in 250 ml developer both from jobo and agfa which would correspond to one 220 roll in film area. This in a cpa with 1500 series drum.

 

This is why i suspect you might suffer some contamination. maybe there's some nooks and crannies in hose-joints that might hold solution. Good luck troubleshooting your atl!

Take a look at Bj�rn R�rsletts lens pages. He is a professional nature photographer with very good reviews of lenses (and excellent tutorial on UV and IR photography)

 

<a href="http://www.naturfotograf.com/index2.html">naturfotograf.com</a>

I know you didn't ask me specifically Dmitry, but when i was snooping for a RA4 receipt to mix my own on usenet i saw claims that romm temp kits had a lot more carbonate (base) in them, I think I saw one source also say to add something like 10 g NaOH pr liter final conc. developer. higher bascicity means higher activity on a developer. Whether the only difference between room temp kits and "normal" is pH, I cannot tell you.

 

An educated guess as to the two layers would be that the solid is carbonate, and the clear layer is TEA (triethanolamine, both a preservative and base in RA4).

 

I personally don't like single concentrates as I have some bad experiences with C41 going sour at the wrong moment. I much prefer having the CD and base separate as this will aid the keeping properties of the chemicals.

 

My 2 cents.

You'd probably increase developer life if you used vertical trays like the Nova processors <a href="http://www.jobo-usa.com/products/novaproc.htm">Nova</a> . They present much less area of your solution to air and thereby minimize oxidation. I made one myself from plexiglas for room temp use (B&W mainly) and it kept Neutol developer for weeks. It also provides very short setuptime, but the original costs way too much, is fragile and hard to clean. The one I made is temporarily out of use due to small leaks. Difficult to get everything perfectly square without proper tools.

 

Personally, I avoid the thing by using drums and preparing what I need for the printing session.

Yes Scott, this is a quest to produce good prints from slides. Yes we know all about the fantastic digtal methods, but still we find it desirable to go against the mainstream.

 

I have tried the slideprinting with frontier. Have had one roll provia printed 10x15 cm, and the prints look good. The film was scrathced the entire length. I have also had some 15x21cm enlargements made from provia 35mm originals; they had visible pixels. Seems the scanning is not up to much more than 10x15 cm for good results. So; the frontier option is not very attractive if you want something big to frame.

Just a small but addition to Ron's procedure; after the first 45" wash, reexpose the print to ambient light while washing for about 1 minute, otherwise you probably wouldn't get a reversal print. I have tried Rons procedure and get decent results using Agfa Neutol NE 1+7 for 2 minutes instead of dektol. If you contrast mask your slides, you will get rather satisfactory prints contrastwise. The only problem is slight mottle you may notice by close examination in even areas such as sky.

Scott, please show us the references you base your claim regarding the decline of amateur neg film while pro film is unchanged. Or are you just guessing?

Dear mr. Troop. I have bought and read your book thorougly and enjoyed it a lot. It certainly taught me much about the photographic properties about many chemicals in a easy to understand fashion.

 

What I dont understand is why you respond like you do towards all those that discuss or disagree with things written in your and Anchells book. I have read all your posts and what you do is start out with a personal attack. Why not discuss the matter instead of the person posting? Defend and explain your work, do not attack your opponents.

 

On topic; glacial acetic acid is not a strong acid. It is a weak acid! It has a pKa of 0.000018, and will of course dissociate to a very low degree. A quick calculation tells you that about 2.3% of the acetic acid is dissociated at 2% concentration. Degree of dissociation will decrease at higher concentrations. Sulphuric acid, which is indeed a strong acid, will protolyze fully in the first step. There is a considerable difference between a strong acid and a weak one. I have spilled both of these acids on my hands by accident, and I consider acetic acid to be a relatively harmless chemical. Much less harmful than the stuff you buy at the supermarket to clean up your drains, which is sodium hydroxide. Strong bases are much more harmful towards human tissue than acids. Still, it is sold and used by people with no formal training in handling chemicals.

 

I would say anyone who cannot safely handle glacial acetic acid safely have no business handling darkroom chemicals at all. There are many developing agents commonly used I would handle with greater care.

 

And for the sake of decency; stop pushing Dr Haist in front of you as your witness of truth. Fight your own wars, do not pull in an innocent third part.

Ron;

 

Is your press kit from Paterson? I have had two kinds of press kit; one which was powder (Jobo? can't recall) and one Paterson (liquid concentrates). The powder kit gave times for 38C and 45C, the Paterson kit (http://www.patersonphotographic.com/chemistry/colchem.html#chrome) gave for a lot of temperatures. Very handy for the press photographer I guess.

 

Maybe contacting Paterson (sales@patersonphoto.co.uk) would give you the information they provide with their press kit as they don't give it on their web page (http://www.patersonphotographic.com/).

Regarding different temperatures and times; I once had a Paterson C41 press kit that contained a list of different temperatures with corresponding times. I am afraid I have thrown that kit as it is spent, but should I find the leaflet I shall post the numbers. I do remember the list was quite comprehensive, but cannot recall how low temperatures they listed. maybe someone else has a kit like that floating about that could help?