how to determine the best working ratio for lenses

[cliveh]

I may miss-understand your OP, but most lenses will give their optimum performance at about two to three stops down.

 

[Dan Fromm]

I'm no expert on lens design by far but I use the Rodenstock/linos/qioptic software for guidance. If you have Pre designer installed then click on systems tab and then the magnifier glass button. Then click in each of the lens elipses (such as double gauss) and see the typical lens element layouts for that type. Which one of those resembles a Plasmat?

As far as I'm concerned a symmetrical type lens is exactly that, a lens which has reflected symmetry between its front and back elements. Maybe Plasmats do, I don't know.

[edit]

did some checking and I think what you refer to as a Plasmat, the Pre designer software calls an Orthometar which may indeed be closer to a Schneider Symmar. But Plasmat and Double Gauss are both Symmetrical type lenses so I think Schneider are using a more generic terminology for symmetric lenses whereas there are in reality more specific design types within the "symmetrical group" of lens types by the look of it.

Um, I just installed PreDesigner 1.28.0. I'm sorry, but it doesn't have a systems tab or a magnifier glass button. I also installed WinLens3DBasic. No relevant lens designs there either. If you want to continue this discussion, please post links to the source from which you downloaded your software.

I'll tell you again. Symmar is a Schneider trade name, not a design type. That's what the word means. Redefining it on the fly is, um, unwise. It covers two different design types. Symmars as originally sold were Dagor (as patented by Goerz and copied by other makers these lenses have six elements in two groups and the two groups are identical. Perfectly symmetrical.) types. In the '50s the original Symmar was replaced by a Plasmat type. The Plasmat is a Dagor derivative with an air space between the inner element and the outer cemented pair. Rarely perfectly symmetrical but there some are. Slowish lenses by modern standards, there are few LF taking plasmats faster than f/5.6. With relatively high coverage, modern ones cover as much as 72 degrees. Plasmats are not double Gauss types.

The original double Gauss type photographic objective is two pairs of meniscii, one pair in front of the diaphragm, the other behind it. All of the elements are concave to the diaphragm. Typical LF 4/4 double Gauss lenses are slow (usually no more than f/6.3 for viewing, f/16 for taking) wide angle lenses that cover as much as 100 degrees. The most commonly-used, until fairly recently, double Gauss types are six element lenses, the basic 4/4 double Gauss with the inner meniscus replaced by a cemented pair. These can be fairly fast (up to f/1.4), rarely cover more than 54 degrees. There are few 6/4 double Gauss lenses for LF cameras. Dallmeyer SuperSix, Zeiss' Planars, Schneider Xenotars, and a few others.

You can reduce your ignorance by buying a copy of, say, Kingslake's Lenses in Photography. Dated, as is his A History of the Photographic Lens (more extensive and a better read), but easier to find and less expensive.

 

[RobC]

I did post a link. See (there was a url link here which no longer exists)

The systems tab is at the bottom of the lens elipses diagram. If you're seeing those then you're already there. Just above the tab is the magnifier button.

I no longer do LF photography but you never know, I may one day so I'll keep your book reference just in case the urge takes me that way.

View attachment 118577
View attachment 118578

And you need to untick some options before you can tick other options which would otherwise conflict so for example you can't tick more than two conjugate options, one field option and one aperture option.

I assume that Dr Geoff Adams who wrote this software knows what he was doing but I'm prepared to be proved wrong on this. The software may well not be inclusive of all families/designs of lenses but this is what I've been using as my reference. He wrote this software for Rodenstock and it used to be available from the Linos website and possibly the Rodenstock website itself prior to that but I can't remember.

 

[Dan Fromm]

Thanks for the link. Yours, dog of an englishman, and mine are both 1.28.0 but mine doesn't have the systems tab that you circled.

This time I was able to download the lens library, used WinLens to look at the designs in it. Not much there, but it is freeware. If you want to look at more types without much text visit www.dioptrique.info.

If you're relying on Experitas' packages no wonder you don't know much. You might want to look for a copy of Arthur Cox' Photographic Optics. Many more design types, with explanations. If you're interested, that is.

Understand too that for practical LF purposes a lens' design type has few implications for anything as long as the lens covers as large a circle as needed.

 

[markbarendt]

all this is on "normal lenses" not macro..
maybe im wrong on this apperture thing,if i am ,please tell me!
normally i would say the same,go out and shoot,but since 4x5 film is not so cheap,i considered a post here..
normally i wouldnt bother you guys with my stupid questions..

Certain stupid questions we like. And even if we grumble a bit here and there we wouldn't be here if we didn't like people like you bothering us. You're doing us a favor.

Your's BTW isn't stupid because it seems to be an honest I don't know.

On aperture, each lens has a sweet range. I have the same 150 and shoot mostly wide open and some as small as f/16. I'm happy with resolution regardless. Like Drew I'd say stop down maybe 2-3 stops or so and its highly likely that it's in its sweet range.

Also regarding aperture, IMO there are really only two reasons to stop down at all, ever: exposure control; DOF control. I work that 150 wide open unless forced to do otherwise. Exposure control or DOF control may force me, diffraction is such a small issue that I simply ignore it altogether.

 

[RobC]

Thanks for the link. Yours, dog of an englishman, and mine are both 1.28.0 but mine doesn't have the systems tab that you circled.

This time I was able to download the lens library, used WinLens to look at the designs in it. Not much there, but it is freeware. If you want to look at more types without much text visit www.dioptrique.info.

If you're relying on Experitas' packages no wonder you don't know much. You might want to look for a copy of Arthur Cox' Photographic Optics. Many more design types, with explanations. If you're interested, that is.

Understand too that for practical LF purposes a lens' design type has few implications for anything as long as the lens covers as large a circle as needed.

I have "Optics, The technique of definition" by Arthur Cox (1956 edition). Not sure if I ever read it. Perhaps I should. But especially for you I shall quote from page 151.

Symmetrical Lenses
The vast majority of lenses to-day are logical developments of two main types, the symmetrical lens and the Cooke Triplet of H.D. Taylor

Seems he thought symmetrical lenses formed a family of designs and goes onto to list some of them.

Sorry to here that you've lost your systems tab. It must be hiding from you.

You might try ticking the "show extra information" check box at bottom of screen.

And when you exit the software save your settings (it will ask) so it starts up next time with those settings

 

[Dan Fromm]

Sorry to here that you've lost your systems tab. It must be hiding from you.

It could well be hiding, but I can't make it appear. I've tried everything but sacrificing a virgin.

Re y'r quotation from Cox, you're cherry picking to defend an indefensible position. Just for you I pulled out my copy (Expanded Edition, 1971). Take a look at the lens cross-sections in the back of the book. Cox groups them for convenience, not by design type or by lineage (as in design B was derived from design A, C from B, ...). It isn't safe to treat all of the lenses in any of Cox' categories as equivalent.

"Symmetrical types" covers many quite different families. His "wide angle" section contains many lenses that are symmetrical, including the original 4/4 double Gauss type. Cox was English, has a slight bias. The first double Gauss lens was invented by Alvan Clarke, a US telescope designer, and sold by B&L as the Alvan Clarke Lens. Rudolph's Planar, which Cox reports as the first double Gauss, is an elaboration of Clarke's design.

Re bias, possibly nationalistic, in books on lenses, see, e.g., H. M. Brandt's The Photographic Lens. Brandt pays little attention to lens makers in the UK.

 

[RobC]

I don't think that cross reference exists in my edition. Cherry picking? I haven't had time to read the whole book this evening and just picked his opening statement which is in agreement with what I said, or rather what I said was in agreement with what he said. I have no doubt that designs have gone their own paths since then but are still essentially of the "Symmetrical" type. Schneider may well have used "Symmar" as a design brand specific to them but the data sheet element layout sure looks pretty symmetrical to me.

Again, tick the "show extra information" check box at bottom of screen. Exit the software saving settings and restart. And always maximise the software to full screen as soon as you start it. There is a bug in it which I have reported several years ago but they haven't fixed it. I guess he was more interested in creating the android app version which isn't as good and doesn't show a lot of stuff which is in the desktop version.

 

[Dan Fromm]

Dammit, symmetrical isn't a design type.

 

[RobC]

Dammit, symmetrical isn't a design type.

Now don't get worked up. I said it was a family and I would like to point out that you gave me the Cox reference and now you're dissing it.

 

[ic-racer]

Close up photography and Large Format film is for some special effects with limited depth of field. If you stop down to equal the depth of field of a smaller film format you will always loose out with the larger format camera due to diffraction as you know. The best cameras for close up are actually digital cameras with very small sensors. Like cameras you could put on an insect, etc.

 

[Dan Fromm]

Now don't get worked up. I said it was a family and I would like to point out that you gave me the Cox reference and now you're dissing it.

It isn't a family in the sense of lineage (b derives from a, c from b, ...). It is just a convenient, for some, category that has only one useful implication. Lenses that are exactly symmetrical -- front cell identical to rear cell -- have the property that at 1:1 some aberrations are perfectly corrected. Lose perfect symmetry and this property goes away.

I'm not dissing Cox, I'm dissing you for misusing Cox.

 

[Dan Fromm]

Close up photography and Large Format film is for some special effects with limited depth of field. If you stop down to equal the depth of field of a smaller film format you will always loose out with the larger format camera due to diffraction as you know. The best cameras for close up are actually digital cameras with very small sensors. Like cameras you could put on an insect, etc.

ic, I get the same DoF on 2x3 at 1:1 and f/16 marked (f/32 effective) with my beloved 100/6.3 Neupolar as I do on 35 mm at 1:1 and f/16 marked (f/32 effective) with my equally beloved 105/2.8 MicroNikkor. The difference between the two shots is that with 2x3 I get more of the field in the frame.

Getting the same DoF on different formats is easy. Just shoot 'em all at the same magnification and aperture.

Giving in to the temptation to shoot at a higher magnification on a larger format than on a smaller can be difficult ...

 

[markbarendt]

Close up photography and Large Format film is for some special effects with limited depth of field.

And one of those special effects is tilting the plane of sharp focus. Movements actually can allow large format cameras to use a narrower depth of field while still getting all the important subject matter in focus.

 

[monk]

Certain stupid questions we like. And even if we grumble a bit here and there we wouldn't be here if we didn't like people like you bothering us. You're doing us a favor.

Your's BTW isn't stupid because it seems to be an honest I don't know.

On aperture, each lens has a sweet range. I have the same 150 and shoot mostly wide open and some as small as f/16. I'm happy with resolution regardless. Like Drew I'd say stop down maybe 2-3 stops or so and its highly likely that it's in its sweet range.

Also regarding aperture, IMO there are really only two reasons to stop down at all, ever: exposure control; DOF control. I work that 150 wide open unless forced to do otherwise. Exposure control or DOF control may force me, diffraction is such a small issue that I simply ignore it altogether.

Your words made me smile behind the screen Mark!i can assure you,i will keep doing you favors),cause im willing to get better in L.F..there is nothing else i want more!!
except health and love around me and nature.
may i ask you what was the biggest print you made(or saw other peoples work live)with this lens thats sharp even from a close line per mm inspector inspection?
so diffraction is out of the game
Thank You Mark!
AlltheBest!

 

[monk]

ic, I get the same DoF on 2x3 at 1:1 and f/16 marked (f/32 effective) with my beloved 100/6.3 Neupolar as I do on 35 mm at 1:1 and f/16 marked (f/32 effective) with my equally beloved 105/2.8 MicroNikkor. The difference between the two shots is that with 2x3 I get more of the field in the frame.

Getting the same DoF on different formats is easy. Just shoot 'em all at the same magnification and aperture.

Giving in to the temptation to shoot at a higher magnification on a larger format than on a smaller can be difficult ...

Thanks for sharing your experiences Dan!makes a sense what you say(like always,on All the forums i saw )
Cheers!

 

[markbarendt]

... may i ask you what was the biggest print you made(or saw other peoples work live)with this lens thats sharp even from a close line per mm inspector inspection?

Because of the physical limits of my enlarger 16x20; I am confident that the prints would look sharp at 32x40 if I had had the room, paper, and trays to print larger. The films have generally been HP5plus and TXP 4x5, printed on a very low tech enlarger with a cheap enlarger lens.

Your biggest challenges with regard to the resolution and sharpness of your photos is going to be your ability to focus well (and of course camera shake). If you need to stop that 150 down to get the test target for your line per mm inspection into focus, you are hooped. DOF is a range of acceptable, not absolute focus; absolute focus is only the thickness of a single point in space.

There are numbers that you can find to define the DOF range but in the end the size of that range is defined by you.

 

[RobC]

Greetings All!
could somebody tell me how could i determine the best working ratio fom my large format lens?
and also i would need some light on the closeup photography subject..
as far as i know for example,if you make closeup-macro shots than your lets say f8 is f22,your f32 is f128 (where diffraction works too).the numbers i made up,but in theory is it something like this?am i right?
if so,what is the "limit" where this takes place?
i have a schneider 150 symmar convertible,a 300mm f8 nikkor,and a 65mm f8 schneider.
could some of you guys help me in this question?
Any help-idea is appreciated!
Thanks a Lot!

Have a good light everyone!

You need to look up the "Rayleigh Criterion" or "Rayleigh Limit" which is the physical law of optics which determines the maximum resolution obtainable at any aperture.

For white light the rounded off limits are:
f-no - resolution (line pairs per millimeter)
45-35
32-50
22-70
16-100
11-140
8-200
5.6-280
4-400
2.8-560

Above figures are taken from Zeiss Camera Lens News No 2.

for 1:1 magnification you get.

65mm lens at f8 effective aperture is F16. CoC is 0.022mm. lp/mm is 114
150mm Lens at f8 effective aperture is F16. CoC is 0.022mm. lp/mm is 114
300mm Lens at f8 effective aperture is F16. CoC is 0.022mm. lp/mm is 114

the three sets of figures above are taken from the Pre-Designer software I pointed you to and are not rounded off but are close to what the zeiss rounded figures for F16 say so I think you can assume both sets of figures are correct.

So whilst you say you are not a lp/mm kind of guy, when you ask a question about resolution which is measured in lp/mm then the only meaningful answer you can get is one in lp/mm. Whether you know what to do with that information is another matter but if you are going to use a technical camera where these things matter then you better start learning about the technical considerations.

Note1: Each stop smaller is approx 27.5% less lp/mm of resolution

Note2: Above figures are theoretical and only relate to the focus plane. If you are prepared to accept a larger CoC (less resolution) then you will get wider depth of field at that reduced resolution. The software shows you what the theoretical values are. You need to consider how much you need to enlarge the negative. i.e. thr print size you require and whether lp/mm will give you the desireable lp/mm in the print which is 5 lp/mm plus with a margin of error added so you really should be aiming for 10 lp/mm in the print even though you're unlikely to get that if you are working at the limits.

Note3:
if you close your 150mm lens down to F32 then:
150mm Lens at f32 effective aperture is F64. CoC is 0.086mm. lp/mm is 29
but your depth of field in the subject has risen to a whole 11mm from 0.7mm. However you should still be able enlarge the neg by X3 and get a sharp print with dof area and probably x4 at a push.

Note4:
Using tilts and swings you may get you a lot more of your subject in focus but that introduces other abberations which will reduce the theoretical limits above.

It ain't as easy as just saying what are the limits, it depends what you do and how precise you are at doing it. In short just setup the shot and check your ground glass at atking aperture which is damn hard becasue you can't see it when lens is closed down so you have to guess or know the numbers or use your experience to know what is about right.

 

[Dan Fromm]

To expand on Rob's point, resolution on the negative or chip isn't really what matters. What matters is resolution on the final print. Enlarge a negative n times, resolution in the final print will be (resolution on the negative)/n. That's for a perfect enlarging lens, in practice resolution in the final print will be somewhat less.

The minimum resolution needed in the final print for it to seem sharp (viewing distance 10 inches, viewer with normal vision) is generally accepted to be 8 lp/mm. Some people on the 'net hold out for minima as low as 5 lp/mm.

Rob neglected to mention that his calculations give the diffraction limited (= best possible) resolution on axis. The limit is smaller off axis. He also neglected to mention that the contrast falls as resolution increases. And finally he didn't point out that attaining nearly the theoretical maximum resolution, even on axis, is very difficult. On this point, see https://www.flickr.com/photos/nesster/4424744296/sizes/o/ and https://www.flickr.com/photos/nesster/4424744224/sizes/o/).

Rob brought up the dread circle of confusion. If you think a little, you'll see that the CoC selected limits how much the negative can be enlarged. Pick too large a CoC and you're guaranteed a fuzzy final print.

The point of all this is that DoF attainable in the final print is limited by how much the neg is enlarged. How much the neg can be enlarged is limited by resolution on it. There are very real limits that bite hard.

 

[Dan Fromm]

ic, I get the same DoF on 2x3 at 1:1 and f/16 marked (f/32 effective) with my beloved 100/6.3 Neupolar as I do on 35 mm at 1:1 and f/16 marked (f/32 effective) with my equally beloved 105/2.8 MicroNikkor. The difference between the two shots is that with 2x3 I get more of the field in the frame.

Getting the same DoF on different formats is easy. Just shoot 'em all at the same magnification and aperture.

Giving in to the temptation to shoot at a higher magnification on a larger format than on a smaller can be difficult ...

Mental slip. I meant resisting, not giving in. Sorry.

 

[monk]

it all makes sense what you guys say,thanks a lot!
and yes Rob,i still have lot to learn,but thats the reason im here

 

[DREW WILEY]

It's all relative. I personally never print a film like HP5 bigger than 3X enlargement no matter how good the optics. But it is a film I've shot a lot of in 8x10. Tri-X is just too gritty for my taste. Those films would be among my last choices for big enlargements from 4x5. But to each his own. One just has to get on the road and start printing to evaluate such preferences. I find all the math lens nonsensical if one doesn't know yet how to even attain a precise film plane to begin with, or how to set up a precise enlarging station. People will spend thousands on this or that camera lens, go use a glassless negative carrier in the enlarger, and then blame the optics! Or the paper will buckle in the easel.
Each step along the way has to be ironed out.

 

[monk]

It's all relative. I personally never print a film like HP5 bigger than 3X enlargement no matter how good the optics. But it is a film I've shot a lot of in 8x10. Tri-X is just too gritty for my taste. Those films would be among my last choices for big enlargements from 4x5. But to each his own. One just has to get on the road and start printing to evaluate such preferences. I find all the math lens nonsensical if one doesn't know yet how to even attain a precise film plane to begin with, or how to set up a precise enlarging station. People will spend thousands on this or that camera lens, go use a glassless negative carrier in the enlarger, and then blame the optics! Or the paper will buckle in the easel.
Each step along the way has to be ironed out.

i understand your point DREW!and you are totally right!
(btw..im on the road for a while but first i did everything alone..with the help of books.this is my 3rd post here,asking the Community what He thinks.and to be honest i got the answers i wanted,basically,that i have to learn-experience more..much morebut im not willing to stop,so it will come.
im here to get better,to understand things,im not here to ask for formulas,that i can use in my work,no..
im here asking questions,to understand things and implement the answers to use them my own way..
may i ask what is your chosen film for big enlargements?you wouldnt go with tmax 100?
AlltheBest DREW!
monk

 

[DREW WILEY]

Sounds like you have the right attitude. Many things about large format photography simply have to be learned a step at a time. So it takes
a bit of patience. But I've personally found each step to be fun and rewarding.