What is a process lens ?

[charles_ou]

I have a Linhof technika V camera body, and I am looking for lenses

for landscape and portrait with my Linhof body.

I knew from Rodenstock website that APO-Ronar lenses are process

lenses.

What is a process lens ? What are the advantages and disadvantages of

process lens ? Please help me. Thanks.

[donald_miller1]

Process lenses are lenses which are primarily designed for the graphics industry. They are flat field lenses which are optimized for 1-1 reproduction. That being said, many of the process lenses are excellent large format landscape lenses if stopped down. Examples are the Schneider G Claron lenses. Normally a process lens will be mounted in a barrel (shutterless). These may be mounted into a modern shutter by Steve Grimes. Or may be shuttered by using a Packard shutter. Considering that large format lenses are usually used with smaller aperatures in usage conditions, a Packard shutter may be a viable and relatively inexpensive option. I have a 305 mm Repro Claron which I use on my 4X5 and it is sharp. I hope that this provides you with the information which you need. Good luck and have fun.

 

Regards,

 

Donald Miller

[robert_a._zeichner1]

Process lenses were used in the graphic arts industry for making color separation negs for printing plates. The things that most distinguish them from camera lenses is that they are apochromatic, which means they can bring three colors (wavelength groups) into sharp focus simultaneously, keeping the size of each separation equal and they are corrected for optimum use close up as opposed to infinity. Many of these lenses make great camera lenses as when they are closed down to f22 or f32 can be incredibly sharp at infinity. They are usually a little slower than camera lenses, but I've never found that an impediment to focusing. There are many of these around as the advent of scanners has rendered them unecessary for most plate making applications and it is possible to front mount them with an adapter into some of the larger shutters (Copal 3 or Universal 4). Check out Steve Grimes web site for a tutorial on how this is done. I use an Apo Ronar 14" that I had him mount in a shutter recently and it's one of the sharpest lenses I currently own.

[kelly_flanigan1]

Process lenses are what we use currently on our process camera that is 17 feet long; and has a 4x8 foot copy board. The illumination is with 6 KW pulsed Xenons. Our APO Ronars are 14,24,36 inch focal lengths. The lenses are stopped down to F22 because of field curvature that is IS a property of the APO Ronar lens. <BR><BR><h3>This urban legend of the process lens being a flat field is wrong.</h3><BR><BR>Process lenses are "flat field lenses when they are used at their <b>working apertures of F22. </b>When the lens is at F9, F11, and F16; the corners are not as sharp as the center; Refocusing will pull the corners sharp; but then the center is amock.<BR><BR> Closing down to F22 is what the lens maker (Rodenstock) and process camera maker (Acti Camera) recomends for the proper usage of this lens. All our tests over 2 +decades also support that F22 is the best aperture to mask the field curvature of the Apo Ronar Process lenses...It takes along time to set the camera up and shoot a negative; using F22 insures the negative is tack sharp at the edges and the center..........<BR><BR>

 

Our process camera holds the negative flat with a vacuum plate. The original is held flat on the copyboard. Both the copy board and the film holder are parallel to a very close level. The copy board is positioned along the 17 foot rail by a dial caliper to within 1/1000 inch. <BR><BR>

 

The primary goal of a process lens is zero distortion; it is usually a symmetrical lens design.<BR><BR>

 

The field of focus at the negative is flat when the lens is stopped down to its working aperture of F22. This is for very critical fine details on maps; and not some dreamy landscape photo with a low detail level.........<BR><BR>

 

Process lenses are "flat field" when at their working aperture of F22; not at wide open. Somehow the web has screwed up and distorted the basic knowledge about process lenses.

 

Read the warning sticker below that is on an <BR>actual working process camera; </B>and learn something about "field flatness" that is achieved only when stopping down the lenses. The data sheet from Rodenstock on our process lenses also states this fact too.<BR><BR>

 

<img src="http://www.photo.net/photodb/image-display?photo_id=1238354&size=lg"><BR><BR><img src="http://www.photo.net/photodb/image-display?photo_id=1238404&size=md">

[jim_galli4]

Many of us who can't afford the latest and greatest have found "process" lenses to be very viable alternatives that can give excellent results for a lot less $ and often weight and size although at the expense of maximum aperture. Most are f9 max. A great treatise that will answer many of your questions is <b><a href="http://www.wisner.com/myth.htm">here</a></b>.

[Ed_Ingold]

Process lenses are designed to work at a 1:1 reproduction ratio. This affects coverage as well as optical quality. A 6" process lens for 4x5 will vignette badly at normal distances (< 1:8 ratios.) You'd be better off with an 8" (200mm) or longer lens.

 

Field curvature or chromaticity may lend a "dreamy" atmosphere to landscapes or portraits. That's not necessarily bad.

[robert_davis2]

"A 6" process lens for 4x5 will vignette badly at normal distances (< 1:8 ratios.)"

 

Only if it's a normal process lens. Wide process lens can cover quite a bit.

[roger_michel]

kelly -- i thought you had sold that beast. or did you have a second one??

[kelly_flanigan1]

The process camera of ours is built into our building. Currently I have been mounting my "dinky" 4x5 speed graphic on the frame; and using the lights and copy platen to shoot artwork. The main rail is about 17 feet long; and 18" square cross section. To move the camera costs more than it is worth; so I have no plans on scraping the beast at all. The elecrical circuit to the camera is 240 volts @60 amps! There is a rotorary 90 degree sector shutter behind the lens mounting plate. Typical exposures for lith film (asa 6) are 10 seconds @f22 ( f44 actual fstop when 1:1)

[jahosopher_jahosaphat]

Another question about process lenses, How suitable are they as an enlarger lens? Must they be used only at f/22 or more closed? I am wanting up to 14X magnifications of 8x10 film, I would expect this to be an ideal enlarger lense (even over a Rodagon) to minimize or eliminate color fringing because of it's APO construction, which I assume is crown and flint elements, (yes, no ?) Thanks JJ

[kelly_flanigan1]

Here we tested a process lens; camera lens; and enlarging lens all at 1:10 ratio. We shot a with a 4x5 camera rigidly bolted to our process camera. The 135mm Schneider Componon was alot better than our 150 mm F9 process lens; at any aperture. Our old kodak Ektar 127mm F4.5 eas the best at the very center; and worst at the far edges. We shot a 30x40" test object/pattern; the image was 3x4 on the negatives. Process lenses are sharpest at 1:1 to about 1:5 <BR><BR>the primary goal of a process lens is zero distortion; so maps can be shot in sections; and fitted together. <BR><BR>A process lenes can be used as an enlarging lens; but the resolution is usually lower; but the distortion better; ie lower.<BR><BR>The lith material of a process camera darkroom are of extremely high contrast. Most ancient pre WW2 lenses are uncoated; later ones are usually single coated. A process camera lens can be UN-coated; abit dusty; and still yield contrasty images; with super contrasty lith materials. <BR><BR>