Condenser or Diffusion Enlarger

KenS

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David,

When 'transmission'.electron micrographs it is almost essential that you make the prints using a POINT SOURCE enlarger (as opposed to the negatives exposed using a 'scanning electron microscope)to ensure that the fine detail from the extremely thin sections can be 'resolved' on the print made from the EXTREMELY thin sections. I spent many days making B/W enlargements from negatives for the electron microscopist when I was employed at the nearby Agriculture Canada Research Center.
The Point-light source light in a 5x7 Durst 138S was also used for making the occsional B/W negatives from microtomed sections of the 'slide-mounted' fixed and stained soft tissue.... usually far superior to what can be recorded when using a camera mounted on even the 'highest' quality bench-top microscope.

Ken
OOps!!! I forgot to mention that when point source light is used, the lens is always used wide open rather then using the f-stop for 'brightness"... which is done by regulating the voltage using a rheostat, thus you have to make sure the image is properly 'in focus' at the time of exposure
This you have LITTLE to NO Depth of field 'freeway' when it comes to focussing the image.
Ken
 

martin henson

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Over my head, as a mere mortal I got better prints from a diffuser than condenser as long as I developed the film to suit the light source, bye the way Ken I did not understand one word as to what your saying, why does things have to get so complicated :p
 

David M

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An enlarger is a machine for casting a shadow, the shadow of the negative, onto the baseboard. As we know from the outside world, a small light source, such as the sun, or car headlights, gives harder-edged shadows than a large lights source, like overhead clouds or net curtains.
A point-source casts very hard edged shadows. Thus, it will reveal the finest detail that the lens can resolve. I once knew why the lens has to be wide open, but I've forgotten. I have used a Vickers Projection Microscope, which is really just a rather specialised reflection enlarger, which used an arc-lamp. That gave point-source light on the specimen, and the optical system had no diaphragm.
I did know someone who devised a point source flashgun, by wrapping the tube in foil and making a pinhole in it. This would cast a shadow of his hand right across a room, where all the finest hairs were clearly visible. A sort of lensless enlarger, perhaps.
This wasn't the purpose. It might have been to record micro-turbulence in moving fluids. It wasn't good for the flash tube.
 
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KenS

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Should you have access to 'both' a condenser and diffused light source enlarger the one negative will rarely produce an exact same contrast print from either using the same grade paper. Thus one is 'required' to develop your film for 'type' of the light source you are using when you are making enlarged prints. Negatives for condenser enlargement will (most often) require a slightly 'lower contrast' negative acquired by a shorter developing 'time'.

Ken
 

Alan Clark

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As an interesting aside to those values that David posted, lately I've been following Steve Sherman's technique of developing to a Zone VIII density of about 1.0, and doing split grade printing. This workflow provides a subtle, but clearly visible difference in what the digital world calls micro-contrast. I believe this particular print characteristic is revealed because you're actually using more of the blue light picking up those deeper tonal values. However it works, it's an interesting technique to play around with that I've only recently started doing.
I first came across split-grade printing, using grade 0 and 5 filters, about 20 years ago when I saw a demonstration given by Roger Parry who at the time was the owner of Paterson. He didn't recommend it for general use; rather as a rescue job for high contrast negatives. I tried it a few times but couldn't get anything different from what could be achieved with the usual careful selection of the right filter grade for the job.
Later, Les Maclean took it up, but said he got the best results with a high contrast negative. It made absolutely no sense to me to deliberately produce high contrast negatives just so you could use a split-grade technique that gave no different results to regular printing methods with user-friendly negatives of fairly low contrast.
So I am interested in what Alan is saying here, especially as I always thought that Mr Sherman achieves his high micro-contrast through stand development of the negative.

Alan
 

David M

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Almost all the legend and lore about printing seems to date from the days when multigrade was not an option for the serious printer and minute attention was paid to levels above FB+F and development for different enlargers. My suspicion is that much of this can be accomplished by modest changes in filtration and for the faithful, splitting their grades in different ways.
This is not to deny that each photographer will fine-tune their own process, from spreading the tripod legs to banging the nail in the wall, in order to get the results they prefer. After all, there are multiple ways to control contrast.
 

Alan9940

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@Alan Clark, Steve uses and teaches his EMA technique for developing LF film; not stand development. His developing technique provides a compensating development which leads to more pronounced edge effects. During the "resting cycles" the developer exhausts itself in the high densities, while continuing to work in the low densities. If you're interested, Google "Eberhard effect" and you can read about Mackie lines, etc.

I don't have enough experience, yet, to speak authoritatively about what is happening when using split-grade printing along with negatives designed using Steve's techniques, but I think what's happening is that the lower high value negative density allows for a relatively short 0/00 filter exposure to properly print these values, while allowing a longer exposure with a #5 filter or blue light to drop in the shadows and blacks. Imagine some textural area of an image, printing straight with, say, a #2 filter might reveal the highlight side as textured white while the shadow side falls at Zone V print value. If using split-grade printing with a properly designed negative, the highlight side will be the same as the previous printing, but the shadow side will drop lower in print value; hence the look of a more textured area.

I think it's extremely important to understand that what I'm talking about can only be revealed using a properly designed negative; basically, as Steve teaches it. I don't believe a normally processed negative that's printed using any split-grade technique will reveal the same final image. If you're interested, I would highly recommend surfing over to Steve's powerofprocesstips.com and looking up his YouTube videos. I vaguely remember that he did a video showing his print results back when he first introduced the EMA premium video series.
 

David M

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I know that this is a trivial question, but why does Mr Sherman wear a baseball cap in the darkroom? It's clearly a considered choice, because he matches cap and shirt on every occasion, so he must have a whole library of caps.

Wikipedia is very scanty on Eberhard. Clicking through to the entry on Mackie lines directs you to try for Edge effects (photography) which leads to a page which says "This page does not exist."

[And how does he get developer into those tubes?]
 

Alan Clark

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Alan, thanks for the reply. When I said "stand" I actually meant "semi-stand", though there may mot be a lot of difference in the finished result.
Regarding your print with a grade 2 filter, if you get detail in the highlights but no dark tones, then one answer may well be to resort to split-grade printing. But you might just as easily solve the problem by moving to a filter that will give more contrast. A no. 3 perhaps....Apologies if I sound sceptical about split-grade printing. When I tried it it seemed to offer no advantage over what I was already doing. But when it comes to the creative side of printing there are no prescribed rules. So if you get something useful out of it, then that's fine.

Alan
 

David M

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Very interesting. Thank you. Page 77 is the place to look.
I had thought that I understood this, but the Eberhard effect seems to be something different and new to me. It looks like a logical corollary of the same mechanism
 

Alan9940

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I know that this is a trivial question, but why does Mr Sherman wear a baseball cap in the darkroom? It's clearly a considered choice, because he matches cap and shirt on every occasion, so he must have a whole library of caps.

Wikipedia is very scanty on Eberhard. Clicking through to the entry on Mackie lines directs you to try for Edge effects (photography) which leads to a page which says "This page does not exist."

[And how does he get developer into those tubes?]
The caps, etc, are probably "props" while doing the videos? Maybe, he's bald? :D

The way I get developer into the tubes (in the dark) is to use a wide mouth funnel making it simple to avoid pouring down the side of the tube and/or missing altogether. And, when I say "funnel" they are actually something used in a hospital that my wife got for me. I forget they're original purpose.
 

Alan9940

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@Alan Clark, yeah, but using a #3 filter to increase contrast is going to affect the print globally; the high values will see that contrast boost, too, and, maybe, that's not what you want. I guess another way to look at it is that Steve's method will produce more apparent contrast in the mid-tones. Simply changing filters and doing global exposures is not the same thing. But, as you said, we all print differently and I'm sure there are photographers out there who can produce a very similar print using a single filter or, heck, even graded paper.
 

David M

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Well, I have pink head, but it seems it cause no inconvenience other than maybe an extra pound a year on sunscreen. Curiously, Ben Horne seems to wear a hat all the time too. Is this a USA thing?
Best not to find out what hospital things were used for, but you're right – it was "in the dark" that bothered me. Presumably any kind of sealable tube would do the job. Perhaps the thick walls provide some temperature stability.
Off to B+Q...

World-class prints on graded paper? Who could believe that? As likely as a picture of the Moon being famous.
 
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David M

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Here's reference to a home-made multigrade head, using LEDs. It seems to work well, but the technical details seem scanty.
 

KenS

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We forgot to mention the ultimate condenser machine – the point source enlarger. Not a practical proposition for printing images, but it's example of the extreme limit of available devices. I found I preferred a diffusion source, but I'd also switched from an anonymous crackle-finish machine with a pantograph (and alleged auto-focus) to a De Vere, so having an enlarger that I really liked may have influenced me. Once you've experienced the waist level wheels, you never want to go back.
Surely the only change needed is to add a half minute, or whatever, to development times? I don't doubt that martin-f5 gets the strong blacks that he likes but I don't quite understand the mechanics of it.

David,

I've just 'found' this post.

I believe 'point source' enlargers were designed/marketed for use when printing negatives exposed using an electron microscope.
when 'working' one to two day a week were spent printing negatives made with these expensive machines. The PS one is FANTASTIC for making B&W negs from 'chromes' exposed with a microscope microscope.

Ken
 

Ian Grant

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From memory Langford may have the charts in either Basic or Advanced Photography.

Ian
 

David M

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It's not a perfect analogy, but I've found that most people can understand the difference as being rather like the difference between a spotlight and a floodlight.

Before clicking on "Post reply" I began to wonder if a point source would reduce, modify or remove the effect of staining in negatives.
 

David M

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Out of curiosity, I did a google search and found this. Although it looks very thorough, I don't know if it answers the immediate question, but I was surprised to find that both its authors are women.
I'm posting it because photography is often considered to be a very blokey activity.

 

Keith Haithwaite

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Out of curiosity, I did a google search and found this. Although it looks very thorough, I don't know if it answers the immediate question, but I was surprised to find that both its authors are women.
I'm posting it because photography is often considered to be a very blokey activity.

According to the preface page (worth reading) it is the modern and updated version of the Ilford Manual of Photography.
 
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