Which f.stop to use . Agitation of negatives

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I am teaching myself in my own dark room and was wondering what aspects to take into consideration when choosing the f.stop on my enlarger. Also there are no instructions on the chemicals i bought on how to agitate whilst developing and fixing my films. I am using Barkley chemicals and vary my films. Any guide lines?

-- stephie driver (stephie9000@hotmail.com), August 21, 2001


Yes, try reading some books on the subject.

-- Alec (alecj@bellsouth.net), August 21, 2001.

Ideally, you want to use the fstop at which the lens is sharpest. For most modern lenses, that will be one or two stops from the widest. However, you also want the exposure time to be long enough to dodge and burn. I like to stay in the 15 to 30 second range for the basic exposure. If you find that exposure times are very short when the lens is one or two stops from wide open, you may want to use a lower wattage lamp, or attach a neutral density filter to the lens.

In a small tank it is typical to agitate for 15 seconds immediately after the film goes into the developer, finishing with a sharp rap on the bottom to dislodge air bubbles. Then agitate for 5 or 10 seconds every 60 seconds. You want to provide enough agitation for uniform development, without agitating so much that the edges of the negatives are over developed.

-- Chris Ellinger (chris@ellingerphoto.com), August 21, 2001.

Focus with the enlarger lens wide open and then close it 2 or 3 full stops to achieve a good balance between sharpness and depth of field. Questions regarding film development are more appropriate in the Film & Processing Forum where you might find your answer among questions already asked. Most public libraries have a good selection of books on the subject (not sure about libraries in UK). Also check the manufacturers web site (Kodak, Ilford, etc.).

-- Michael Feldman (mfeldman@qwest.net), August 21, 2001.

While Alec's response might have been a bit abrupt, he does make a point. There are tons of books on the market or in your library that will cover photography. Read a few. You'll be amazed at how much easier it is to learn from a good book than by piece-meal question and answer.


-- r (ricardospanks1@yahoo.com), August 22, 2001.

Once you have established the optimal printing aperture on your enlarging lens, don't touch it. Focus with a properly adjusted grain focusser (or a parallax focusser if you prefer) at this aperture, to prevent focus shift during printing. Some of my students could not make sharp prints out of cracking sharp negatives because they focussed with the lens wide open, then stopped down to whatever aperture used for printing.

-- Samuel Tang (samueltang@austarmetro.com.au), August 22, 2001.

You must have some very poor enlargers if the aperture cannot be adjusted without changing the focus. If you have this problem, get a new enlarger (or fix the one you have). Focus with the lens wide open, the same way you do with a camera. Then stop down to the desired f/stop, usually 2-3 stops down.

-- Michael Feldman (mfeldman@qwest.net), August 22, 2001.

Maybe not a bad enlarger, but a crappy lens. None of the popular high quality enlarger lenses (Rodagon, Componon-S, EL-Nikor) show focus shift. The focus change is less responsive (and thus less accurate) if the lens is stopped down.

-- Tim Brown (brownt@flash.net), August 22, 2001.

Mark Callf was kind enought to give me a hint than made me understand f.stop on an enlarger:

Deep of field is not the issue, since you are talking about an objetc without volume (the negative). Some people might say that using a close f.stop might guarrantee focus even with a negative holder a bit twisted, well Ild say change your negative holder.

Sharpness of a lens is an issue, and it is true that almost all lents are sharper around mid range of f.stop. I have a Leitz Focomat with a 40mm lens and it is sharper at 2 stops bellow wider position.

Exposure time is also an issue selecting the f.stop. My focomat does not have the problem of short exposure times, in fact, one of the only negative aspects of the Focomat is its not strong light. I have now lerned to use a wider f.stop (even if it is not the sharpest) to avoid real long exposure times in big enlargments.

So, select the f.stop that is sharpest, and dont move it unless your exposition time is jeopardizing your work.

PD I have never seen a lens that needs refocusing at diferent f.stops. (nor in camaras or enlargers) I suggest that when movin the f.stop, try not moving the focus by accident.

-- Paco Cacho (pacocacho@yahoo.com), August 22, 2001.

Paco, I beg your pardon, but depth of field IS an issue in enlarging. Most people do not have perfectly aligned enlargers (alignment of baseboard, easel, lens, and negative) in all planes. Even if the negative carrier is aligned, many people do not use a glass negative carrier to ensure an absolutely flat negative. If you think that your enlarger is perfectly aligned, then I suggest you try a laser alignment tool to correct your misconceptions.

Fortunately, however, most enlarger lenses are the sharpest about 2 stops down from wide open, which also gives adequate depth of field.

-- Michael Feldman (mfeldman@qwest.net), August 22, 2001.


You know what? you just placed the seed of doubt in my enlarger. You are totally right that it is tought work to aling all elements. I had always consider alignmetn as something sure. I will double check it. In that case, then I guess IT IS valid to play safe and use a closer aperture when posible.

-- Paco Cacho (pacocacho@yahoo.com), August 22, 2001.

Paco, I think we are in agreement here. We both agree that 2 stops down is the sharpest f stop and it offers adequate depth of field. But I would suggest that you check your enlarger anyway, even if only with an $8 torpedo level. I was shocked to find that my enlarger was not in alignment with my baseboard. A few shims under the front of my enlarger column fixed that problem easily. Another area that needs attention is the lens board, which on enlargers that have spring loaded boards, can easily be out of alignment. This can be fixed with a simple hand adjustment.

-- Michael Feldman (mfeldman@qwest.net), August 22, 2001.

I have to chime in here! I have a Zone VI enlarger and the %@$%!@^% thing is always out of alignment, I finally decided it was easier to purchase a Versalab laser alignment tool than to put up with the agravation of out of focus prints! So, Michael is correct, depth of field does matter when enlarging and even at two or three stops from max aperture if your enlarger is terrible misaligned ( like mine always was) then closing the aperture won't help you one bit!

-- Jorge Gasteazoro (jorgegm@worldnet.att.net), August 22, 2001.

In response to Alec and Ricardo. I am a full time student doing 30 hours/week with a part time job. This way it is easy to find answers at the click of a button as i am often on line (at uni and home), rather than to spend the time trawling through books in the librery, lug them home and find out i can't quite find the answer. Also thanks everyone for your answers especially Paco and Michael you banter was ammmusing and informative.


-- stephie driver (stephie9000@hotmail.com), August 23, 2001.


You are quite right, after all what is the purpose of a forum like this if we all had time to go to librarys, bookstores etc? You can spend many hours looking for information from those sources and never find what you're looking for. The best way to find the best f.stop for your enlarger is to procure a grain magnifier. Then using this with a negative that is sharp from edge to edge try the different f.stops until you find the sharpest grain in the centre and then again on the edge etc. until you reach the best setting.

For agitation on TMax and Delta films I have found a more aggressive agitation i.e. make quick flips to be best. With the other films I find a more gentler agitation is better. As suggested agitate for the first 30 seconds and then about 3-5 agitations every minute or 10 agitations every minute.

-- matt veld (mv@ezysurf.co.nz), August 23, 2001.


I too have a Leitz enlarger (V35) with the 40/2.8 Focotar lens. I have found that my best f.stop is about half way between f4 and f5.6. That has been the same for two of these lenses I have owned. Are you aware that this lens can be used in stepless mode? A lot of people own them and aren't aware of this fact. One guy even had the click stop part removed from his Focotar 40/2.8 when all he had to do was pull down on the lens to make it stepless.

-- matt veld (mv@ezysurf.co.nz), August 23, 2001.


"As suggested agitate for the first 30 seconds and then about 3-5 agitations every minute or 10 agitations every minute."

Sorry that should read 'agitate for the first 30 seconds and then about 3-5 agitations every 30 seconds or 10 agitations every minute.'

-- matt veld (mv@ezysurf.co.nz), August 23, 2001.

Regarding changing the aperture on the enlarging lens, I feel that you are confusing the issues of depth of field and depth of focus. Anyway the late SaltHill enlarger employed a top quality Schneider lens with fixed aperture to ensure optimum result: it wouldn't allow the user to diminish the quality of the final print by using a less-than-ideal aperture, or focussing at full-bore and then stopping it down.

-- Samuel Tang (samueltang@austarmetro.com.au), August 23, 2001.

Good for SaltHill, whatever that is. The remaining 95% of the world's high quality printers focus with the lens wide open and the stop down to an aperture that yields a good compromise of edge-to-edge focus and lens sharpness. The same way it's done with a camera.

-- Michael Feldman (mfeldman@qwest.net), August 24, 2001.


Yes, I have used the steepless aperture of the lens, its a nice feature.

What has happened to me is that once I focus, if I move a lot the f.stop, i tend to move the focus. I havent been able to lock the focus. Any trick Im missing with the Focomat?

-- Paco Cacho (pacocacho@yahoo.com), August 24, 2001.


Mine is the same. There is a allen head screw behind the part that holds the neg carrier that can be tightened (right side looking from the front). This makes the lens focus stiffer but unfortunately then the autofocus function doesn't work too well; not that I use this overrated feature much.

Beautiful enlargers though. The bulbs can reduce in brightness over time and a new one can make a big difference to exposure times. I nearly bought a Schneider 40/2.8 HS Componon which is reputed to be even better than the Leitz (at least in the contrast department), might still when I'm a little more flush.

I would really like the Splitgrade module but they run close to $US1K.

-- matt veld (mv@ezysurf.co.nz), August 25, 2001.

That should read "left side looking from the front".

-- matt veld (mv@ezysurf.co.nz), August 25, 2001.


What is the diference between "deep of field" and "Deep of Focus" ?

I asume they are two ways of calling the same efect. They both recall on the fact that on closer aperures on the diafragm, the sharp focus can be achieved in a wider range between two imaginary glasses. This can be applied to the lens in a camara or the lens in an enlarger. Now, lets face reality, you dont get sharp focus in a range. You get sharp focus in a puntual distance from the lens, and from there you start to loose focus in objects closer or farther from that punctual distance. A wide aperture makes you loose focu very dramatically, and therefore you can say that the two imaginary glasses are very close to each other (short deep of field). A close aperture, allow you to loose focus not so dramatically, and you could say that those two imaginary glasses are far apart from each other. But, sharp focus is punctual distance, not range of distance.

This is well undestood in a camara. But I didnt quite get it in an enlarger... I always asumed that since you had a flat negative, you didnt have to worry about this, but now I realize that the lens is curved, and the negalite is flat, so you can loose focus on the edges of the negative since they have a diferent distance to the enlarger lens that the center of the negative. This is pointed correctly by Micheal Feldman (and with a lot less words).

What im not so sure is that you can translate deep of focus for the image COMMING OUT of the enlarger lens and to the paper. Can a close aperture help you obtain focus quality even if your paper is a bit unalligned??? Im not so sure...


I foud the allen bolt (right... left, watever), Ill give it a try. have also been seduced by the Splitgrade, but as you recall it, its big bucks... I have a stupid question. I have a color module on my Focomat V35, and when doing B&W, I just turn the dials to cero on all three colors. But I figure... Is there a combination of yellow, blue and red to enhance B&W? or going beyond... Is there a group of combinations that could emulate splitgrade contrast control??

-- Paco Cacho (pacocacho@yahoo.com), August 27, 2001.

If you can't find the time to go to a library or bookstore & check out some of the information available I doubt you will really do much with your images. Go to a library & check out some of the basic books. This is not a recipe driven pursuit like mediocre cooking. Go and check out a basic book or three on B&W film processing and while you are at it look at the works of Edward Weston, Morlay Baer, Alfred Eisenstaedt & so many others who learned both the craft and art of photography. You obviously have some interest but will need to get rid of the 'I want it without having to work at it' attitude if your work will progress. This stuff really looks easy but takes a dedication to craft and vision both if you are to be anything more than a picture taker.

-- Dan Smith (shooter@brigham.net), August 27, 2001.

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