Chris, You have to admit one thing.....the respondents on this LF site (Alan, R on, Steve, Ellis, and others) are the most incredibly courteous, patient, and ge nerous (as well as knowledgeable) people you will find anywhere. Sergio.
Chris, You have to admit one thing.....the respondents on this LF site (Alan, R on, Steve, Ellis, and others) are the most incredibly courteous, patient, and ge nerous (as well as knowledgeable) people you will find anywhere. Sergio.
Ron, I wasn't suggesting that they make only one 150mm lens. Only that if they comput e the optics for every single lens individually, rather than a common design, th e lens ranges might be more useful. Your comment that a 150mm design for 4x5 whi ch is expanded will make a good 8x10 lens is a good point -- if manufacturers m ade 3 versions of different designs for 4x5, 5x7 and 8x10. But they make a lens in 10 different lengths, some of which are a tad too small image circle for 4x5, and also therefore having gaps in the long lens product lineup because they hav e no narrow angle of view lenses. I don't want to and shouldn't need a 5 kg , $1 0,000 lens just because I want a 600mm lens on 4x5.
Sergio: I'll agree with your statement, but does it have anything to do with len ses? :-)
Chris, LF lenses are a specialty market; Your reply smacks of frustration with the manu facturers, but keep in mind that there are other options: you don't want to spen d $10,000 for a 600mm lens (by the way a Nikon Nikkor T 600mm f/9 telephoto is l isted in the B&H book at US$2499.00)? Fine, buy a 6x7 or 6x9cm roll film back fo r US$450 (6x7)>$750 (6x9) and you will have effectively turned your 300mm M-Nikk or into a 600mm ( or near it.). one of the beauties of large format is that one can crop, sometimes radically (see Arnold Newman's portrait of Igor Stravinsky), and not lose much image quality. Something you cannot do with smaller formats. there really is a different way of thinking to LF photography as you will find o ut, then there is to 35mm work. Both can complement the other -Ellis
No, I'm not really frustrated Ellis. I'm just trying to understand why things ar e the way they are. I've never seen anyone bring up the topic of why LF lenses a re designed this way.
Chris, I have a feeling that you haven't seen the subject brought up because in the over all scheme of things, it doesn't matter.
Large format photography is a lot different than miniature (35mm)photography, in a lot of ways. I think you will find that LF photographers tend to do a lot mor e, and talk a lot less, because, there isn't a lot of the type of information av ailable that there is for 35mm photography.
LF uses a lot of older equiptment, how many 35mm photographers use a 100 year ol d lens for thier primary optic? I and a lot of others do. I would be hard presse d to tell the difference between an 8X10 contact print made with my freinds lat e model 300mm Fuji and my 90 year old 12" Turner and Reich Convertible.
I don't know the specs for the Convertible, it covers 8X10 with all the movement s I have available, and if it didn't I would take it back to the gentleman that sold it to me and get one that did. I make that arrangement before I even start to haggle price. LF can be very daunting in that respect, we fly blind quite a b it. This forum is a good source of accurate information, and frustrated or not, I think as you start to create some images, you will find that the specifics of lens design will have nothing to do with your creative output.
Wait until you start to retouch dust and lint out of your negatives, you'll see what I mean.
LONG response to Chris: With all due respect, I don't believe anyone could real ly satisfactorily answer your question as it's been posed, though many have trie d. To quote Strother Martin, from Cool Hand Luke, "Boys....I think what we have here....is a failure to communicate!". So, let's set up a few basic parameters here, before going any further. You stated, the various focal lengths within the Schneider SA line (or G-Claron, or Apo Symmar lines) all have wildly differing image circles, yet they pretty m uch have the same angles of view. Don't confuse angle of view with angle of cov erage. Other respondents have explained this important difference very well, re view their responses.
These differences may not make any sense initially, but this is a very good thin g. It is for the consumer's benefit. They are not just saving money, or taking the easy way out.
As you know, each of the LF film sizes (4x5, 5x7, 8x10, etc.) requires a specifi c image circle size to adequately "cover" the particular film area in question. Adequate "coverage" is simply determined by the diagonal measurement of the fil m size in question; the distance (expressed in mm's) from the opposite corners o f the film area, plus about 20% extra to allow for displacement of the image cir cle due to LF movements.
A lens is said to adequately "cover" a film size when the image circle it projec ts onto the film area, at infinity focus, and stopped down to about f16 or f22, provides even illumination and image quality across the entire film plane, corne r-to-corner. Any more "coverage" than necessary for the film size in question i s a waste of lens capacity.
The closer you focus a lens from infinity, increasing the distance from the noda l point of the lens to the film plane, the larger your image circle becomes. Th at is why all image circle dimensions are given at their smallest usable size: a t infinity focus. (Note: Schneider often provides image circle dimensions for t heir G-Claron lenses at closer than infinity focus; the huge image circles somet imes quoted for G-Clarons are given at magnification ratios of up to 1:1, double the bellows extension needed for infinity focus. Schneider touts these lenses a s optimized for close-up work.)
Another misconception about image circles is that they get physically larger as the lens is stopped down from maximum aperture. Image circles do not increase i n size as the lens is stopped down to f16 or f22 from maximum aperture; the illu mination just becomes more even, and the image quality gets better, across the e ntire image circle, as the lens is stopped down to apertures of f16 or f22. (So urce: Schneider Optics)
Now, to apply this, let's say that my favorite focal length in 35mm is my 50mm, or "normal" lens. I want the equivalent focal length when I use the 4x5 format. Conversion tables tell me I need a 150mm LF lens to achieve the same angle of view for the 4x5 film size.
I check all the manufacturer's product literature and find several lenses in thi s focal length: the G-Claron 150, the Nikkor 150 W, the Apo Symmar 150, the Apo Sironar-N 150, the 150 Super Symmar 5.6, the Super Symmar 150 XL, the Nikkor 15 0 SW, the Grandagon 155, and many others. Why all the choices? Am I being play ed by the manufacturers? I'm confused!
Remember, all these 150mm's will provide the same angle of view when used on the 4x5 format, not the same angle of coverage. Additionally, all will vary wildly in their respective sizes of image circle, their physical size (filter and shut ter size), and their prices (from several hundred to several thousand dollars). Which one should I choose?
From a "user's point of view", if I had a bottomless bank account, strong and wi lling porters or beasts of burden to carry all my equipment, and a 4x5 camera la rge and strong enough to handle any 150mm lens available, I could choose any of the above lenses for a "normal" lens for the 4x5 format. But why choose, and pa y for, a Super Symmar150 XL, or a Nikkor 150 SW, for 4x5 format? Why not the G- Claron or Sironar N?
From a "user's point of view", if I wanted to do studio tabletop/product photogr aphy work, I'd get the G-Claron--lot's of coverage when focused closer than infi nity, and optimized for close-up work. If I wanted a versatile field lens for g eneral landscape/portraiture work, I'd get the Apo Symmar, or Sironar N, or Nikk or W--great image quality at infinity, light, small and cheap, and more than suf ficient coverage for the intended purpose: 4x5. If I were a "perfectionist", an d wanted the sharpest "normal" lens made for 4x5, I'd get the Super Symmar 150 5 .6, damn the cost! And If I were a complete fool, I'd get the Super Symmar XL, the Nikkor 150 SW, or the Grandagon 155.
To summarize, Chris: When choosing a LF lens, in a particular focal length to a chieve a particular angle of view FOR a specific film size, for a specific photo graphic purpose, that will adequately "cover" the film size in question, I shoul d/would choose the lens brand/design that will do all these things for the most reasonable cost, weight, and size. Anything else would be wasteful.
The only exception to this common sense rule would be if you wanted to use the s ame lens on a different size format; to achieve a different angle of view on tha t format, of course. In that case, you could conceivable get a 300 Nikkor M for both 8x10 and 4x5, providing a "normal" angle of view for the 8x10 format, and a "short telephoto" angle of view (comparable to about a 100mm lens on a 35mm ca mera) for the 4x5 format.
Have any of you noticed the increased use of this forum lately? Is it just the heat outside? Or is it the "All Monica, All the Time" crap on TV these days?
Hope this helps, Sergio.
Thanks for your response Sergio, I learnt several good points from it.
I do understand the difference between angle of view and angle of coverage. Perh aps I can crystalise my question even further by putting it like this... The Schneider Super-Angulon 58mm XL has a 166mm image circle. The Super Angulon 90mm XL has a 259mm image circle. I can see several possible reasons for this... .
1) A big image circle is more useful on a 90mm lens than on a 58mm lens? 2) A 72mm lens with a 259mm image circle would cost so much they wouldn't sell a ny? 3) They can't make a 72mm lens with a 259mm image circle? 4) They are just being lazy by using the same optical design for the 58mm and th e 90mm lens and that's just how it happened to pan out? (Both lenses have a 110 degree angle of view)
1. Yes, for a given film format, I find larger image circles more necessary for longer lenses, because Scheimpflug needs more tilt, and controlling parallel lin es needs more shift.
2. The size, weight and cost of an LF lens will be largely dependant on the angl e of coverage. And cost varies with volume.
3. The current design limits for rectilinear lenses are about 120 degrees. This depends on the definitions of acceptable aberrations and fall-off, as well as ty pes of glass and manufacturing methods.
4. Being lazy? It seems to me that designing lenses is a computationally difficu lt process. And pushing the envelope, 120 degrees and wider, is also a marketing issue: what trade-offs will the market bear?
If I was a manufacturer of LF lenses, I think I would take advantage of, say, a new glass formula or new manufacturing process to design a new series of lenses, that could do something more than my previous series of lenses. The market seem s to want ever greater angles of coverage. I suspect there is also a market for pushing other envelopes, for example getting high quality at larger apertures. P erhaps Schneider et al don't think that market is large enough.
For point 1., I can see that you would need less tilt for Scheimpflug effect for a shorter lens. But I would have thought you would need _more_ shift for a shor ter lens. The shorter the lens, the closer you will need to move to your intende d subject, and I would have thought therefore the greater shift. I'm imagining b eing right up close to a tall building.
Yes, you are right, for the same magnification, a shorter lens will be closer to the subject, and will need more shift. Slightly confused thinking on my part: I was thinking of the situation where the camera position didn't change.
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