lens optimized for smallest aperture

[RobC]

So there we have it. Dan says process lenses are good for landscape work. Or rather Dan believes that they are based on what Rodenstock say.
Personally I don't.

 

[Luis-F-S]

Dagors f/45

 

[Kawaiithulhu]

How do you kill a zombie?

kill -9 <<process-id>>

Winner of the thread. Pun intended.

 

[Dr Croubie]

Zombie or not, I've got a similarly related question.

I have, through a long process of GAS, somehow acquired a Componon, Comparon, Apo-Gerogon, G-Claron, and Xenar (f/4.5), all in 150mm.
According to their respective literatures:
Componon are regular enlarging lenses, working 5-15x or so.
Comparon are slightly cheaper, but work in the 2-6x enlargment range (where it's harder to spot the difference to a better lens, apparently).
G-Claron are optimised for 1:1, but Schneider claim they apparently work just as well at infinity (I haven't got a 150mm Apo-Ronar, but I've seen the literature that claims the same of them).
Apo-Gerogon are also process lenses for 1:1 work, I haven't seen anyone claim they're good at infinity (nor much of anything else about them, tbh)
Xenar of course are 'general purpose' lenses, which I'm presuming to mean 'non-macro-optimised'.

So the question is, G-Claron is optimised for 1:1, the Comparon then Componon are optimised for larger (paper), then the G-Claron can work again at infinity.
This is LF and you don't get 'floating element' focussing like 35mm/MF (except for the spacing washers on Docter Apo-Germinars), so I accept that not everything can be optimised for every magnification at once.
But what about the G-Claron at 10x, if it's ok for 1:1 and 1:inf? Or the Componon at infinity or 1:1?
There's obviously nothing stopping me just testing them (except time and inclination), one boring sunny day I may just do that.
But on the theory side, is their 'performance' limited to that narrow an enlargement range?

And more to the point, what exactly does 'optimised' mean in these circumstances?
The only datasheet that specifically rates performance vs enlargement factor that I've seen is the Apo Ronar that graphs barrel distortion (at 1:1 it's obviously flat, outside that it's worse but it's not a retrofocus 35mm lens by any means).
I'm presuming that lp/mm figures in there somewhere but I've never seen claims nor data.
Or is, as some suggest, the whole lot just marketing speak? (in which case I'm strapping my EL-Nikkor 50mm to my EOS 3 and shooting hyperfocal from now on.)

 

[RobC]

my bet is that the xenar will work the best at infinity compared to the others.
Optimised is a term usually reserved for enlarging lenses in my book and I inlclude process lenses in that. I have assumed it to mean closest to apo, i.e. the broadest band of wavelengths focus to same point at the optimised magnification ratio.

And it is quite easy to visually see the degradation in a print when magnification goes much above advertised optimum range. It is not so easy to see when it goes below advertised optimum range.

 

[Ian Grant]

Rob, ancient (1960s) Rodenstock propaganda recommended using Apo Ronars at all distances, claimed that they were superior to contemporary telephoto lenses.

Nikon propaganda says this about dialyte type Apo-Nikkors:

Please adjust your beliefs.

Nikon seem to be saying similar tp Rodenstock and Schneider about using Process lenses at infinite distances but interesting they say wide picture angle while Rodenstock say superior to contemporary telephoto lenses.

There were illustrations in UK published book in the 70's comparing a Process lens to a normal plasmat type of the same FL and in a situation with significant DOF the flat field process lens distorted closer spherical objects noticeably. But then not all process lenses are the same type, some were Tessar type, others Dialyte and some plasmats so your adage of needed to try a lens for yourself is important.

The Scheider shutter mounted G Clarons were supposedly better optimised for working to infinity.

Yes, they are called process lenses and are optimized to work at smaller apertures. They are intended to make color separation negatives but can be used for general photography. They are NOT cheap.

I've always found process lenses quite cheap because of their slower apertures, except perhaps for one or two specific lenses like late Apo Ronars.

Ian

 

[RobC]

I don't think you can have it all ways. As I understand it, symetrical type designs work very well for low magnification ratios as in enlarging lenses but not so well for distant objects. So what type of design do these process lenses that work for landscape images have?

 

[Richard S. (rich815)]

Hi All

Are there any lens types that are optimised for high stop/deep focus not specifically macro
as in a lens that performs better at f64 than if dose at f11 for example
I know that normal lenses will suffer with diffraction at high stops and normally perform best a couple of stops down from wide open

thanks

robin

There a British landscape photographer from the 90's (cannot recall his name right now, I have his book somewhere) who shot practically all his photographs on Hasselblads at F/22. They were wonderful. He did not seem to let the theory/fact of diffraction get in the way, nor did his results! Sharp as all get-out. It's still there of course but heck if it mattered....(like many things in photography).

 

[Richard S. (rich815)]

There a British landscape photographer from the 90's (cannot recall his name right now, I have his book somewhere) who shot practically all his photographs on Hasselblads at F/22. They were wonderful. He did not seem to let the theory/fact of defraction get in the way, nor did his results! Sharp as all get-out. It's still there of course but heck if it mattered....(like many things in photography).

Ah, found it. Charlie Waite, and it was this 1992 book below. Each photo has the f/stop and speed used and like I said almost all were fully stopped down. I remember at the time thinking, "but what about diffraction?" and then answered myself as I viewed the images: "who cares...?"

 

[Ian Grant]

Look at it from a different perspective, Dialyte lenses have always been known for their high definition and overall sharpness and good corrections. Kodak sold their 8"/203mm Ektars which give excellent performance at Infinity through to 1:1. Before lens coating though they were more prone to lower contrast and flare than Tessar type designs.

Many are using Process lenses on ULF cameras where negatives are only contact printed and are very happy with the results. There's so many different Process lenses that it's something individuals have to try for themselves because it's highly subjective in practice.

The most popular process lenses are G Clarons but the cell spacing is slightly less on the shuttered versions which improves performance at Infinity. There's a post-WWII CZJ long FL process lens that has quite a wide spacer that you remove to use the lens at Infinity.

I've not yet got around to testing a 150mm G Claron against a 150mm Geragon (modern Cooke Triplet) 150mm CZJ (T coated) Tessar and my 150mm Sironar N, I need an exacting subject to see what differences there really are.

Ian

 

[RobC]

I had a pet theory, some years ago, that the point at which diffraction became significant in a lens was when the aperture diameter reached between 5-7mm.

So based on my theory which was not based on any sound scientific proof, the optimum aperture for the following lenses would be approx:

focal length]	approx aperture	approx theoretical filmresolution lp/mm
50	8.0	229
85	14	125
100	16	109
150	25	68
210	35	47
300	50	31

 

[Maris]

I had a pet theory, some years ago, that the point at which diffraction became significant in a lens was when the aperture diameter reached between 5-7mm...

I've got a similar pet theory. I call it the 3 millimetre rule:
If the end point of the photograph making process is a full frame 8x10 image (or thereabouts) a lens aperture of 3mm or larger will ensure that the diffraction in the image is finer than eye can see.
By extension, if the final product is a 16x20 then the aperture has to be 6mm or bigger ... and so on. Here is an example:

Snow Gum Dance, Charlotte Pass.
This is an 8x10 contact from a Fomapan 100 negative exposed behind an Apo-Nikkor 610mm lens working at f128. Detail finer than the eye can see? Yes!

 

[RobC]

Yes these pet theories seem to pinpoint the so called sweet spot of a lens where you get the best balance of diffraction and resolution.

 

[Ian Grant]

There have been threads about this before (on the LFP Forurm) but John sexton used f32 50% of the time and f45 another 20% in one of his 5x4 series of images and this is the same with some of his other work. The old rule of thumb years ago was always the lowest marked aperture would be diffraction limited and less than ideal.

The manufacturers optimise 5x4 lenses for f22, Zeiss first stated that f22 was the optimal aperture for critical work with their Tessar lenses before WWII and from extensive use of LF Tessars (& type) that's true corners/edges are fractionally softer at f116 but that softness then increases as you open up.

Ian

 

[RobC]

its all very dependant on all the factors involved. The lens manufacturers alway quote figures at infinity. If you are focussed at say 10 feet then the numbers change so there is no hard and fast rule unless you do the maths at every focussing distance and even then its dependant on each particular lens and how well they perform as the aperture widens.
The main consideration is the magnification ratio for enlargement. I added some approx on film resolution numbers to table above.
So for example, if you were using a 300mm lens for 8x10 film you would get approx 31lp/mm at f50. That doesn't seem like much but if you are only making a 20x16 print so 2X magnification then its plenty and a 3X enlargement would work too.
Again with a 150mm lens for 5x4 then at f25 you get 69 lp/mm on film which is enough for 6X enlargement so a 30x24 inch print.
So its really a question of making sure you have enough on film resolutoin to make the enlargement size you need which I use 10 lp/mm as requirement. i.e. divide on film res by 10 to give max enlargement factor you can use before you will run into potential problems with image degaradation due to over enlargement. My approx figure of f25 is close to what they are saying. i.e. A physical aperture diameter of 5-7mm is about where it should be be unless you are doing very big enlargements in which case you are likely to run into other lens aberation problems depending on the quality of your lens which is where the lenses for smaller formats win except that you need bigger enlargemeent factors so its swings and roundabouts.
You need to find the "syetem" which works best. Its not just a question of doing the maths because one lens for 35mm may out perform another lens for medium or large format for the same print size.
Then it comes down to technique becasue if you have sloppy technique then a larger format negative will cover a lot of bad technique to a point.

And when you look at the whole "system" you must of course take into consideration your enalrger setup where a huge amount of resolution can be lost becasue of poor alignment and enlarging lens effective aperture. Take a 35mm neg using a 50mm lens. If you make a 18x12 print (12X enlargement )and use f5.6 on the lens, the effective aperture is f61.6 which means you only get 30lp/mm in the print which is enough. But only if your enlarger setup is perfect and neg is perfectly flat and aligned etc.
Since most setups aren't perfect you'll maybe get a good print but you may not. With a 4x5 neg and 150mm lens at say f8 making same size print ( i.e. a 4X enlargement) you'll get 76 lp/mm in the print which is over twice as much print resolution which leaves a lot bigger margin of error to play with. i.e. the bigger neg will cover a lot of bad technique and still produce a decent print. Not surprising everyone says bigger negs produce better looking prints until you look at why that might be. My suspicion is that its poor technique, specifically alignment and keeping camera still, that is the real reason until you get to 30 inch prints and bigger where you do need a bigger neg due to lack of resolution required in the smaller format neg. Unless that is your camera lenses and film are capable of capturing the required resolution and you have the technique to do it which most of us don't.

And note that 35mm film resolution is typically quoted as less than 200lp/mm and in reality you'll be doing very well to get 100 lp/mm on film so that is a big limiting factor to how much you can enlarge. 10X and you've hit the practical limit unless you have been an absolute perfectionist at every stage using the best lenses and the right film, dev and everything else.

 

[RobC]

Yes, they are called process lenses and are optimized to work at smaller apertures. They are intended to make color separation negatives but can be used for general photography. They are NOT cheap.

But why would they need to be optimised for smaller apertures? If you are working with an enlarger going from flat field to flat field then what is the advantage of smaller aperture which gives theoretical lower resolution?

I guess maybe because you are only using central portion of lens which the best resolution except it will be lower becasue of smaller aperture but perhaps more even across whole image.

 

[Jim Jones]

Decades ago, before the convenience of digital calculators, I went through all the math concerning resolution, f/stops, and diffraction. The results agreed fairly well with RobC and Maris, about 5mm . However, theory and math aren't the only important consideration. It has been claimed that Edward Weston shot some close-ups at f/256 where DOF was more important than line pairs per mm. I agree. Some subject matter may dictate a need for optimum sharpness, while Stieglitz' equivalent photographs of clouds had no fine detail except for perhaps the grain in the film. That brings up another subject: slight diffraction limiting in an enlarger may smooth out grain. I'll leave testing for that up to someone else.

 

[Richard S. (rich815)]

Decades ago, before the convenience of digital calculators, I went through all the math concerning resolution, f/stops, and diffraction. The results agreed fairly well with RobC and Maris, about 5mm . However, theory and math aren't the only important consideration. It has been claimed that Edward Weston shot some close-ups at f/256 where DOF was more important than line pairs per mm. I agree. Some subject matter may dictate a need for optimum sharpness, while Stieglitz' equivalent photographs of clouds had no fine detail except for perhaps the grain in the film. That brings up another subject: slight diffraction limiting in an enlarger may smooth out grain. I'll leave testing for that up to someone else.

Good points. All this testing and "facts" around diffraction and sharpness and so forth is fine. And one could adhere to all the "best" practices and proudly proclaim: "In theory all my photographs are really the best they can be." And no one would care...

 

[RobC]

The person who did it might care but I think the point is to know what is realistically doable witha 35mm systm or a medium format system etc and not to go chasing the unobtainable which you might if you didn't know.

 

[timparkin]

Ah, found it. Charlie Waite, and it was this 1992 book below. Each photo has the f/stop and speed used and like I said almost all were fully stopped down. I remember at the time thinking, "but what about diffraction?" and then answered myself as I viewed the images: "who cares...?"

Having done quite extensive testing of digital and film (medium and large format), f/22 on medium format is similar to f/16 on 35mm. There is a loss of 'biting' sharpness but it's probably hidden by grain anyway. On top of this, most lenses perform best in the corner at between f/11 and f/16 (for 35mm at least).

In our testing of 35mm lenses, f/22 was the point at which diffraction become very noticeable. If you wanted the best rendering across the frame (ignoring 'exceptional' lenses) then f/11 seemed best.

For our large format testing, we saw somewhere between f/16 and f/22 as being the sharpest. Resolution fell off considerably somewhere between f/32 and f/45.

Here's a resolution test of 5x4 Provia (with a test resolution of approx 5um).

f/16 2/3 = 53" long edge print (at 10 lines per mm)
f/22 2/3 = 47"
f/32 2/3 = 43"
f/45 2/3 = 28"

We used the 2/3 stops as the peak sharpness was at f/16 2/3 with our Fujinon 180A

So you can see sharpness dropping dramatically but then again if you're happy with 28" prints f/64 solves lots of depth of field issues..

Tim

 

[Kawaiithulhu]

PS: if you take this concept of very low f/stop numbers far enough you end up with a pinhole camera with useless glass in the way

 

[DREW WILEY]

Interesting thread. Process lenses can be optically superior to typical taking lenses. For example, I know a fellow who specializes in tele-photography,
and puts Apo Nikkor 4-element process lenses on a Toyo 8x10 view camera, then Nikon 35mm film as well as digital cameras at the former film plane. The resolution is superior to conventional telephoto camera lenses. I own a number of Apo Nikkors, which I use mainly in the lab, but also know that they are superior in a number of respects (except portability and standard shutter mounting) to ANY of the regular view camera lenses I own, even at infinity, including Nikkor M's, Fuji A's and C's, dagors, G-Clarons - all stellar performers in their own right. But diffraction is the great equalizer. F/256 might be fine is you're making a contact print. But my personal custom realative to modest enlargements is to never go smaller than f/64 with 8x10 film (and preferably not below f/45), f/32 with 4x5, f/11 with 6x7, and considerably less for even smaller cameras. Otherwise, if depth of field can't be managed, learn to use a view camera with plane of focus controls, or at least a tilt macro lens.