I FINALLY Understand... Bokeh & Aperture Roundness

Mustafa Umut Sarac · Apr 3, 2012

I am trying to find as much as possible from web on lens design and I found something interesting. If you research soft focus lenses , there are
two trends , two lenses lenses as a double gauss relatively close each other and there is one trend consists two lenses are distant from each other. And there are two very thick lenses trend.

Double gauss is used at Summicron , Summitar , Summaron , second is viewable at Elmar , third is at Glatzel Zeiss lenses.

In my belief , Legendary german lenses have two groups in their construction and function.
First of all , an soft focus lens and secondly other lens elements for correct focused image.

I think that soft focus lens corrected for off focus , aberrated bokeh area.

There would be 3 graphs at modern patents which illustrate the error of correction at focus , out of focus and distant out of focus.

Its a xy graph and shows how distant cast the light focus out of this ideal xy graph.

Lens designers design and understand how their or others lens create a photograph value.

MTF test is nothing when compared with this test.

Umut

Brian C. Miller · Apr 3, 2012

Old-N-Feeble said:
Okay... if "some" spherical aberration is necessary to produce nice bokeh then maybe I should be looking for Imagons, SF Ektars, SF Fujinons, etc. I'd only use the discs with the periferal holes closed though. I hate the effect created with them open. I'd definitely use them "stopped down" a bit. Am I crazy or is this one way to get what I want?

Soft focus lenses aren't used for general photography, although the Imagon was advertised as a general-use lens. (I.e., outdoors, product photography, all that normal stuff) Take a look at the LFF post "in Galli style" thread, where lots of older and soft-focus lens images are posted. Figure out what type of image really suits you. There's a representative photograph on the LFF images section from just about every type of lens ever produced.

Here's the problem: nobody really knows what you want in an image. You need to slap some film into your camera, and make some photographs. Then you can quantitatively demonstrate that your lenses behave in one direction, and you need them to go in another. Unless you can point at something in an image and say, "this sucks," then you're just chasing magic silver bullets to slay imaginary monsters.

polyglot · Apr 3, 2012

Grumpy Old Man said:
Hang on, what I actually typed was "I understand it is a function of the way spherical aberration is corrected, or not" - I have added the bold type

Indeed and you are correct.

My post was in reply to the OP, who was saying he wanted to use modern, "highly corrected" lenses and that therefore the aperture would be the limiting factor. In actuality, "highly corrected" and sharp lenses can have quite poor bokeh and it's got absolutely nothing to do with aperture shape. If a lens is over-corrected for SA, a perfectly circular aperture cannot save you from donut highlights and likewise, if it has a just-nice amount of SA, it's fairly irrelevant what the aperture shape is.

There's a reason the world stopped bothering with circular apertures with thousands of leaves; they're pretty pointless.

Old-N-Feeble · Apr 3, 2012

It's really beginning to sound like I can't have my cake and eat it too. One thing I really don't want to do is buy more lenses to carry. Then again, I can't carry them anyway and can't walk far from the car. So.....

John Austin · Apr 3, 2012

Dear ONF,

Without knowing your image requirements or if your income depends on it, I would respectfully suggest you get something small and easy and enjoy your old age

I am thankfully still healthy, active and enjoy using 10x8" in the field, (work for current clients requiring very large silver jelly prints requires it) - But for "family snaps" enjoy a Vitessa as much as anything

What I am saying is that if your income does not depend on it why go to the expense and pain of LF if you cannot get the gear around to the locations you may wish to photograph

A Rollei or 35mm may limit your print size if you require tonal smoothness, but remember the print size limit for Paul Strand was 10x12", EW 10x8" and Thomas Joshua Cooper made 5x7" contact prints

I hope these observations do not cause offense, but if your photography is a hobby why make it painful?

John

photovestad · Apr 3, 2012

It's easy to test the Bokeh of any lens using a Bokemeter. Nikon made a nice one back in the day but they're hard to find. I'm waiting for one to turn up on eBay but haven't had much success so far.

Old-N-Feeble · Apr 3, 2012

Howdy GOM,

I'm going large format because I'm returning to my roots. While I've shot 135 and miscellaneous 120 but I always preferred sheet film.

It's a neurological thing, not so much a physical one, so carrying a 4x5 a few hundred yards from the car is really no different than carrying nothing. For those times that I don't think I can handle a larger 4x5 (Canham Traditional to stitch up to 4x10), several sheet film holders and a larger set of lenses, I do have a lightweight 4x5 (Chamonix 45N-1) dedicated solely to 6x12cm roll film with a dedicated set of smaller lenses.

I'm not poor but I'm far from wealthy. I'm almost embarrassed to list the pricey sets of lenses I've acquired over the last couple of years especially since they probably won't do everything I want them to. At any rate I can afford to buy a few more lenses... just none of those high-priced rare artsy ones with strong cult followings.

Mike

Nicholas Lindan · Apr 3, 2012

Old-N-Feeble said:
none of those high-priced rare artsy ones with strong cult followings.

Then try a low priced artsy one with a strong cult following:

http://re-inventedphotoequip.com/Site/Prices.html

They even come with perfectly round apertures.

You may find, though, that a sink-strainer aperture works more to your liking. You can even use a real sink strainer:
http://www.amazon.com/LDR-501-3220-Drain-Guard/dp/B001EYHKXQ/ref=sr_1_4?s=hi&ie=UTF8&qid=1333501300&sr=1-4

Old-N-Feeble · Apr 3, 2012

Nicholas... any example images shot with these lenses? I don't like the "sink drain" apertures hence my reasoning to use Imagon and Fujinon SF discs fully closed using only the center openings.

Brian C. Miller · Apr 4, 2012

Reinhold Schable's Wollaston Meniscus lens:
http://www.largeformatphotography.info/forum/showthread.php?64954-Miscl-Meniscii&p=868487#post868487
http://www.largeformatphotography.i...0-February-2011-Portraits&p=690998#post690998

BrianShaw · Apr 4, 2012

Old-N-Feeble said:
Nicholas... any example images shot with these lenses? I don't like the "sink drain" apertures hence my reasoning to use Imagon and Fujinon SF discs fully closed using only the center openings.

Here is example of Fujinon SF. Unfortunately I don't remember the exact specs on the exposure. I seem to remember it was Yellow disc about halfway open. Film is likely to FP-4. I think I scanned a contact proof, not the neg. Dust spots is an artifact of the contact sheet, not the neg.

keithwms · Apr 4, 2012

The Mamiya 150 SF may entertain.

Apart from that and similar imagon lenses, you can of course get an LF lens and rip out the aperture blades and make yourself a perfectly round aperture disc. I did this with an old convertible lens and, notwithstanding the 5 minutes of math I had to do to compute the diameters of the openings, it was very easy. I cut the apertures in black slide film. By using a more transparent material you can get interesting mixes of sharp and blur. I have an idea for an electronically controlled item that'd achieve the same effect.

Old-N-Feeble · Apr 4, 2012

When I mentioned soft focus lenses such as Imagon, Fujinon SF, Kodak Portrait, etc. I may have confused the issue. I'm pretty sure those are all cemented doublets and are a little more corrected than meniscus lenses. I mentioned them because they become pretty sharp when stopped down somewhat and show very little glow.

I'm really just looking for lenses with good bokeh or merde or that difficult-to-describe creaminess... whatever we choose to call it. I never fully realized how important this is until recently.

As ususal, when I find something that interests me it will take me a long time to understand and find solutions for it. At the moment I'm sort of grasping at straws. I hope everyone can forgive that.

BrianShaw · Apr 4, 2012

Old-N-Feeble said:
When I mentioned soft focus lenses such as Imagon, Fujinon SF, Kodak Portrait, etc. I may have confused the issue. I'm pretty sure those are all cemented doublets and are a little more corrected than meniscus lenses. I mentioned them because they become pretty sharp when stopped down somewhat and show very little glow.

The fujinon is a 3-element lens, if I recall correctly. When stopped down or used without a strainer it is respectably sharp with not much of a trace of softness.

John Austin · Apr 6, 2012

Firstly, the page from the book by Con. . . .

No, too much crap already, I will PM you

John

I FINALLY Understand... Bokeh & Aperture Roundness

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I FINALLY Understand... Bokeh & Aperture Roundness

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