75mm Biogon sharpness-quality.

[Richard Boulware]

For jj. and anyone else interested, I did check the optical quality of the 75mm Biogon with the 75mm Grandagon-N, last year.

My Biogon is one of the third, and final production runs of this classic lens. Mine has the three rows of tiny square chromed friction patterns on the ring that controls shutter speeds. (Thanks to my friend J.P.Mose for this information).

In direct shooting of a target at a distance of about two and one half city blocks distance, negs were made of both lenses, on T-Max 100, processed in Pyro. Optimum sharpness occurred with both lenses at the classic optical philosophy at two stops down from maximum aperture. The target was a distant townhouse and the leaves of the shutters on the townhouse windows.

Observations were made on what I call 'micro contrast' which I term, the ability of the lens to separate grey tones at extreme enlargements. Negatives were viewed through a 20X binocular medical dissecting microscope over a tungsten light stage within the microscope unit.

My observations are correct, I think, for these two specific lenses only. Lenses can be like identical twins....looking alike, but each having different personalities.

The best way I can give you my observation opinions is to invent some kind of artificial scale to give you an opinion and reference. By doing this...I imagine a quality scale for both resolution and contrast....running from one, to one-hundred. Although each quality...contrast and resolution should be examined separately, I will lump them both together. In my observation, the Grandagon-N 75mm would be scored a 96 on a 100 scale. The 75mm Zeiss Biogon would score abou 93 on a 100 scale. Slightly less for this Zeiss lens, but amazing nevertheless for a lens of this age.

The quality of the Gradagon-N is superb, with multicoating and modern computer design, but I am amazed that the Zeiss lens could even come this close.

Just one mans opinion that I thought I would share with this group.

[Steve Hamley]

Thank you for the report Richard. Seeing old glass doing this well is a pleasure.

Steve

[David A. Goldfarb]

Thanks, Richard. How is falloff of illumination on the Biogon compared to the Grandagon-N?

[John_4185]

I have only a crummy Epson 3200 flatbed scanner, so forgive.

Here's a 38mm Biogon shot for comparison purposes:
elearning.winona.edu/staff%5Fo/jjs/compare/ (http://elearning.winona.edu/staff%5Fo/jjs/compare/)

And here's a 3" Biogon on 4x5
elearning.winona.edu/staff%5Fo/jjs/f/ (http://elearning.winona.edu/staff%5Fo/jjs/f/) (click around on the blow-up of the lower left corner)

Pretty sloppy scanning. I'm really not very good at that stuff.

[David A. Goldfarb]

Thanks, JJ. Looks pretty good, probably better than the Grandagon-N, though I think the Grandagon-N has more coverage.

[Brian Vuillemenot]

Hi Richard,

Good to read- was this the f4.5 or the f6.8 Grandagon?

[John_4185]

though I think the Grandagon-N has more coverage.

Does the Grandagon have as little light fall-off and distortion?

FWIW, this particular Biogon has a circle of coverage of probably around 7", which ain't much, but then Biogons are like that.

[Richard Boulware]

Answers to some of the questions. : 1. David A. Goldfarb. Biogon fall of is non-existent on my 75mm Biogon.. Focusing image on GG is bright and crisp, and same for test negative. Grandagon-N is much the same, although I thought a caught a hint of fall off. The Grandagon-N fall off ...if it is there,....is so slight as to not warrant a reshoot on a gray card, and hauling out my densitometer. Center filters?.....don't waste your hard earned bucks. Guess I am one of those guys who thinks that some illumination fall off in very wide lenses is a creative tool that can be creatively exploited to the advantage of the photographer. No worries, Mate.

Certainly the 75mm Grandagon-N has more coverage, but decades of experience has taught me that 90% of camera front standard tilts are totally unnecessary when shooting landscapes. It's kind of like going elephant hunting with a howitzer. Nice to have the potential but rarely used.

Brian Vuillemenot: The Grandagon-N was a 4.5, brand new, right out of the box. A very fine lens, as one would expect from Rodenstock.

Perhaps I could have done a optical lab, optical bench test, but I like to test lenses in real life, not in some damned lab. No test charts for me. Just shoot something with great detail, at great distance, and use a damned good microscope to evaluate. The image area I was viewing and rating was about 1mm on the negative. That's good enough for me.

Merry Christmas.

[David A. Goldfarb]

Thanks again for the responses. I have the 75mm/4.5 Grandagon-N, so I know how it performs, but was more curious about the comparison to the Biogon of legend. I have a Schneider III center filter that I use with a few different lenses, and I usually use it with the 75mm as well, but even without it, the Grandagon-N is still pretty good. Here's a shot with the 75mm/4.5 Grandagon-N at f:16 on Type 55 with a B+W 022 (medium yellow) filter, no center filter, and about 1.5-2 cm front fall with my Tech V mounted upside down, and the darkening of the lower corners is visible, but not too bad really--

http://www.echonyc.com/~goldfarb/temp/Viewfrom560RSD,12Mar2005.jpg

[Richard Boulware]

jj. Thanks for posting that scan. Sharp enough? I would certainly hope so. I had three Hasselblads when I had my big studio. Once I got the Hasselblad SWC knocked out of my hands, while on assignment in Los Angeles. Luckily I had insurance, and some connections with the guys at Hasselblad. I had the honor of watching a factory technician remove the lens and replace the incredibly intricate magnesium assembly (I think...magnesium) which holds the lens elements. Amazing. Machined out of a solid piece of metal, the three dimensional rig which holds the elements of the 38mm Biogon together is intricate and complex enough to be called...metal art. I left with a new appreciation of why Hasselblad SWC cost so much.

[paulr]

were you looking at portions of the image on axis or off axis?
modern lenses tend to show their advantages the further you move off axis.
and in some cases, the wider you go from the ideal aperture, or the further you get from the ideal magnification.

i wouldn't expect gigantic differences between the biogon and the grandagon (or a super angulon) because they're all based on the same basic design. I'd guess that manufacturing tolerances and multicoating (which would really show up in high contrast situations) would be the biggest differences.

[Dan Fromm]

Paulr, they're not all the same basic design. The Grandagon and SA don't have the tilting exit pupil that Biogons have, consequently have more rapid falloff of illumination off-axis. The SA, in particular, is basically child of dagor.

I can't speak to manufacturing tolerances, but all of the 20 38/4.5 Biogons I've had came from aerial cameras. Each went through at least three different sets of acceptance tests. At Zeiss, before shipping. At the camera manufacturer, before mounting in the cameras. And by the RAF after delivery.

I also can't speak directly to the benefits of multicoating. But the 38/4.5 Biogon, 47/5.6 SA, and 58/5.6 Grandy that I shoot are all single-coated and all quite flare-resistant.

Richard, what you say about the SWC's Biogon is very interesting. The glasses of the F135 Biogons I've had were mounted in fairly conventional cells that screwed directly into the F135 shutter. Unfortunately their dimensions are wrong for standard Compur/Copal shutters, so adapting the lenses for use on a more conventional camera takes a lot of skilled machining. $$$.

Cheers,

[Richard Boulware]

paulr: My observations of the image on the negatives was dead on to about 20 degrees off dead center axis and I kind of averaged the readings.

Dan: Observing the inner working of the SWC 38mm Biogon saw the framework for the cells. It was a one piece assembly that looked like three hoops with four or six stand-off members separating each hoop. The cross sections of each hoop was rectangular, as was the stand -off members which separated them. The technician showed me the one broken stand- off that had been fractured when the lens hit the concrete studio floor. The whole assembly reminded me of the wire hoop frame that women of the 1880's used underneath their dresses...that poofed out their skirts. I remember the technician telling me that this was computer machined from one piece of metal. I was very impressed. Its been a long time ago, but that one machined structural assembly and it's one piece feature, stuck in my mind. I think it would be fair to say that in the machining of that one block of metal, about 95 percent was left on the floor of the lathe room. I wish now, that I had asked to keep the broken assembly. It was a beautiful piece of metal work.

[John_4185]

R. Boulware[ Dan: Observing the inner working of the SWC 38mm Biogon saw the framework for the cells. It was a one piece assembly that looked like three hoops with four or six stand-off members separating each hoop.

I have disassembled the 3" Bigon (not to be confused with the smaller 75mm Biogon) and the body is a series of many steps to hold the lens clusters, however the scale of the particular lens makes it very large, and therefore much easier to hold tolerances, nonetheless quite impressive machining. If there is enough interest, I will disassemble it again and make pictures.

[John_4185]

paurlr i wouldn't expect gigantic differences between the biogon and the grandagon (or a super angulon) because they're all based on the same basic design.

Call me handicapped, but I see profound differences between the Biogon design and the rest.

The Super-Angulons are so far out of the design range of the Bigons that I have to believe you are looking at ... what... alien designs? Really. S/A lenses are just so way different.

[John_4185]

Dan Fromm all of the 20 38/4.5 Biogons I've had came from aerial cameras.

I remember that period. Wish I had one of those today because I now have a focal-plane shutter MF rangefinder and a spare lensmount. Oh no. No more lenses! :)

[Ole Tjugen]

The Grandagon and SA don't have the tilting exit pupil that Biogons have, consequently have more rapid falloff of illumination off-axis. The SA, in particular, is basically child of dagor.

Both Grandagon and SA have tilting exit pupil. Not as much as the Biogon, perhaps?

The SA is far removed from the Angulon, which again was far removed from Dagor. Both Angulon and Dagor are 6 elements in 2 groups, but that's all. (Irrelevant to present discussion) The Angulon is called a "reverse Dagor", which only means that it's -+- where the Dagor is +-+. There is no similarity apart from the number of elements per group.

[Michael S. Briggs]

The Grandagon and SA don't have the tilting exit pupil that Biogons have, consequently have more rapid falloff of illumination off-axis.





As Ole says, this is not correct. Stop one of these lenses down, look at the aperture and rotate the lens axis away from you. You will see that the pupil remains fairly circular. Rodenstock and Schneider publish graphs of the illumination on their datasheets, which show that these lenses perform about as expected (i.e., approaching cosine to the third) for lenses using tilting pupils. And its both pupils. That is why these lenses have such large outer elements, giving them characteristc appearence of two pointed cones connected to a shutter.





The modern extra-wide-coverage lens that doesn't using the tilting pupils method to improve the off-axis illlumination is the Super-Symmar XL.





Here is a previous round about the 75 mm Biogen (and versus other wide-angles): http://www.largeformatphotography.info/lfforum/topic/498241.html.





And a link to a discussion of illumination falloff, with further links: http://www.largeformatphotography.info/lfforum/topic/501033.html.

[Dan Fromm]

Ole, Michael, thank you for correcting my errors.