35mm f/4.5 APO-Grandagon on bigger than 6x6?

[dante]

So I am stumped a little bit.

I have been toying with a new-to-me SW612 with a 35/4.5. I have been shooting it between f/11 and f/16, and I have been observing that where zone-focused, the center is sharp on infinite objects and as you get wider than a 6x6 field, things almost have motion blur. That said, if you zone focused at 2m, everything across the frame at a distance of 2m is sharp. I am trying to figure out what is going on:

1. Not stopping down enough to actually cover 6x12? I know that the coverage of this lens on this format is marginal. But would taking it down a stop or two resolve this? With a short FL, 1/30 of a second is not out of the question.

2. Curved field of focus?

3. Intra-ocular distance off? Doesn't seem to be the case but it does vaguely remind me of what happens with a Brownie when the lens is reversed.

4. Film not flat? This seems like a distinct possibility, since a Horseman 6x12 back curves the film around a roller before you shoot it, and the fact that the depth of focus of the lens at the film plane is more critical with a short lens at infinity, it at least seems possible.

5. Orange filter glass is distorting things off axis? In this shot, it has a 67-86mm plus a Contax MC orange (which apparently is also the cause of the uneven illumination, since it doesn't show up in shots with a straight 67mm filter).

6. Horseman should have been packaging these with 6x9 or 6x7 backs?

The effect is not bad, but if this is normal behavior, I may concentrate my efforts with this camera on 6x9 and not 6x12 (35mm is plenty wide for that format... like a 17mm).

Thanks,
Dante

 

[Leigh B]

The 4.5/35 APO-Grandagon with an image circle of 125mm is rated to cover the 6x9 format.

- Leigh

 

[TimVermont]

Hi Dante,
if it is the lens I think it is, it is only spec'd for 6x9 and requires a center filter. See the Rodenstock archive: http://www.rodenstock-photo.com/Archiv/e_Rodenstock_Analog_Lenses_27-42__8226.pdf#page8

 

[Dan Fromm]

Mine doesn't do that. You've shown us a scan. Is the negative like that?

FWIW, Rodenstock recommends shooting the lens at f/8 - f/11.

 

[Dan Fromm]

The 4.5/35 APO-Grandagon with an image circle of 125mm is rated to cover the 6x9 format.

- Leigh

Really?

 

[Leigh B]

Really?

Really

This is from a recent datasheet that bears the LINOS name as well as Rodenstock.

- Leigh

 

[wiltw]

B&H specs on the 35mm APO Grandagon certainly states, "Image Circle 125 mm @ f/11"

In the Overview text, "The Rodenstock 35mm f/4.5 Apo-Grandagon Lens is a professional wide angle lens specifically for the 6x9 format, providing an angle of view on 6x9 which is similar to a 15mm lens in the 35mm format. "

https://www.bhphotovideo.com/c/prod...ock_160300_35mm_f_4_5_Apo_Grandagon_Lens.html

 

[dante]

Mine doesn't do that. You've shown us a scan. Is the negative like that?

FWIW, Rodenstock recommends shooting the lens at f/8 - f/11.

Fair question, but yes, the neg is like that. The scan is off a Flextight, so film flatness at output is not an issue, and I just rechecked it with a 15x loupe. I only have a 6x9 enlarger, so it's not the end of the world if 6x9 is the usable area. If I get more than that, hey, virtual shift function.

But your point about recommended apertures may be the key; maybe this is on the other side of where the performance is good. Might also explain this hefty 0.9 center filter, which when I tested it against 5 others, was the only one that actually did anything. Maybe I got the wrong impression that this could be stopped down from some old Rodenstock data showing the image circle for various lenses at f/22.

In theory, at least, coverage should not be an issue; a Horseman "6x12" back is only 113mm wide at the film gate, so it's a 125mm image circle. Linhof 6x12 is actually 120mm wide, so no, it wouldn't cover that.

Thanks all for the answers so far!

Dante

 

[Leigh B]

a Horseman "6x12" back is only 113mm wide at the film gate, so it's a 125mm image circle.

The required image circle diameter is the diagonal of the film, not its height or width.

For a 6x9 rectangle, that dimension is 108mm.
For a 6x12 rectangle, it's 134mm.

- Leigh

 

[dante]

The required image circle diameter is the diagonal of the film, not its height or width.

For a 6x9 rectangle, that dimension is 108mm.
For a 6x12 rectangle, it's 134mm.

- Leigh

Leigh, to clarify what I wrote above, the 125mm figure I mentioned (actually 125.6mm) is the diagonal of a rectangle 55x113 (the Horseman 6x12 gate), and 125mm is what the lens is rated for. If Horseman sells this lens with a 6x12 back, I'd assume it works. Or is supposed to. I'm not expecting that it would be perfect in the corners, but I'm a little bit stumped here.

Dante

 

[Leigh B]

Lens coverage is not black and white (pun intended), it's a range of grays.
Quality degrades as you approach the perimeter of the IC.
Each manufacturer has a different standard for the limit of degradation defining the IC.

As a way of compensating for that degradation, I always use the nominal film size.
This puts the degradation generally outside the actual image area.

Plus the calculations don't depend on the actual dimensions in any given camera.
Those dimensions can vary, and may not be accurately known.

- Leigh

 

[ic-racer]

Burn the center of the image or use a center filter.

 

[dante]

Leigh, I understand that you're locked into the idea that a 35 APO-Grandagon covers only 6x9. Let's assume that's right. I'm still trying to debug a problem that starts even within a 6x9 (55x82mm) frame, which is a 98.73mm circle. Is the "perimeter" the last 25+ percent of the stated image circle? That would be one hell of a mulligan for a German optics company.

The most useful things I have taken away from this discussion is (1) it's not normal; (2) the optimal apertures are bigger than I thought.

I'm starting to wonder if ye olde B+W and Heliopan contrast filters with their "non-binding" anodized rings actually unscrewed the front group slightly when I was testing various combinations of 67EW, 67-86mm rings, and 67mm filters for mechanical vignetting - or the massive set of tests of 5 different center filters.That would probably explain the the issues with distance focusing and why on closer examination, the effect seems to vary from roll to roll of film (shot with different filters...). I'll have to test this some more tomorrow when it's sunny out.

Dante

 

[Leigh B]

Leigh, I understand that you're locked into the idea that a 35 APO-Grandagon covers only 6x9.

Dante,

I'm not "locked into" anything. I couldn't care less what the lens covers.
I'm just passing on the published specifications.

As you approach the hard limit of lens coverage, image quality deteriorates.
The IC is defined by each manufacturer based on the tolerable amount of degradation.
We do not know what criteria were used by any manufacturer.

Hold a lens up so you can look straight through it.
You see the aperture diaphragm fully.
Now rotate the lens.
You'll come to a point where the edge of the front element touches the aperture.
That's the absolute limit of full coverage at the film plane.
Now rotate farther.
The edge of the front element intrudes into the aperture, reducing its effective diameter.
Continue rotating and eventually you cannot see the aperture at all.
That's the absolute coverage limit, when no light gets through the lens.

Obviously this ocultation effect varies with the diameter of the aperture.
That's why the image circle diameter increases at smaller apertures.

But beyond that, the lens aberrations may increase as the light angle increases.
These effects can only be quantified if detailed design information is available.

- Leigh

 

[Dan Fromm]

Leigh, there are two coverage concepts floating around. One is "illuminates." The other is "has good image quality in the corners."

You used the limit set by mechanical vignetting as the limit of coverage. That's the illumination concept, I think. My 35/4.5 Apo Grandagon puts light in 6x12's corners. Beyond them, in fact. By your criterion the lens covers 6x12.

By the way, mechanical vignetting is worse at large apertures than at small.

Please look at the Rodenstock apo-grandagon grandagon-n data sheet that's posted here: https://onedrive.live.com/redir?res...35&authkey=!AESpkw0t4oWnLtY&ithint=folder,pdf In particular, look at the 35/4.5 Apo-Grandagon MTF and illumination curves. Per Rodenstock, it gives reasonable image quality at 63.7 mm off-axis. In words, it covers 6x12.

Per R'stock, illumination falls off approximately with cos(theta)^4. Worse than at f/4.5, which points to mechanical vignetting, better than at f/11. At the limit of coverage illumination is down 4 stops from the center, as cos^4 predicts. In words, it covers 6x12. That falloff is better at f/11 than at f/4.5 explains why R'stock recommends stopping down at least two f/ stops when using the recommended center filter. Two center filters are recommended for Apo Grandagons, AR Center Filter + 2.5 E67/86 (the first offered) and Center Filter + 2 E67/86.

Dante, which filters are you using? That image quality varies with the filter used suggests a problem with at least one of your filters.

Make sure that both cells are fully seated in the shutter. Attaching and removing a filter shouldn't move the front element, could unscrew the front cell a little.

 

[Leigh B]

Leigh, there are two coverage concepts floating around. One is "illuminates." The other is "has good image quality in the corners."

Dan,

I addressed both.

You missed my last two sentences, thus:

But beyond that, the lens aberrations may increase as the light angle increases.
These effects can only be quantified if detailed design information is available.

Note the "light angle increases" comment. That means "off axis".
As can be seen from any MTF curve, image quality falls off as you move off axis.

Also please note:

The IC is defined by each manufacturer based on the tolerable amount of degradation. We do not know what criteria were used by any manufacturer.

We cannot know what amount of degradation was considered acceptable by any lens maker.

- Leigh

 

[Dan Fromm]

Obviously this ocultation effect varies with the diameter of the aperture.
That's why the image circle diameter increases at smaller apertures.

This is the illumination concept. The reason that image circle increases (image quality in corner concept) as lenses are stopped down is that off-axis aberrations that are sensitive to aperture get smaller as the lens is stopped down.

 

[Leigh B]

Dan,

If you choose to quote only part of a post you can make it seem to say whatever you want.

That is in no way legitimate or ethical.

- Leigh

 

[Dan Fromm]

Leigh, we're getting nowhere. Let's wish the OP good luck in solving his problem and let this drop.

 

[moto-uno]

^ It was fun while it lasted , thanks for the entertainment .. Cheers, Peter

 

[dante]

Dan, the filters in question are:

- A Heliopan 67mm Yellow 15
- A Contax 86mm O2 via a 67-86mm ring

...so neither of them should be degrading things much. I have seen how the narrower-angle 45mm goes blue in the corners with color film, so it would not be surprising if these filters are exaggerating the light falloff. I also thought for a hot second that the yellow/orange filters might be influencing the focus point (they certainly are capable of doing so with some lenses and b/w digital sensors), but where this is an APO lens, that should not be a factor.

Best,
Dante

 

[Dan Fromm]

Dante, thanks for the reply. Neither of your filters should cause the problem. That the results you get change depending on which filter is mounted still bothers me.

What happens without a center filter and which do you use? I found a CF necessary when shooting 2x3 with E6, can't imagine shooting 6x12 without one. I mean, 6x12's corners are 4 stops down from the center without a CF.

If you're not doing anything silly like shooting handheld you might want to have a qualified shop look at your lens.

I hope that Bob Salomon will jump in. He used to recommend Marflex, who are now closed, as the R'stock service station in the US. I think that Nippon Photoclinic in NYC replaced Marflex, could be mistaken.

 

[dante]

What happens without a center filter and which do you use? I found a CF necessary when shooting 2x3 with E6, can't imagine shooting 6x12 without one. I mean, 6x12's corners are 4 stops down from the center without a CF.

Not using a center filter right now; the one I have is the Heliopan 0.9 (3-stop) that is spec for this lens. Actually, I also have the 0.45, a Schneider IIIb that I use with the 58XL on my Silvestri 6x12, and the Kenko that came with the camera. Only the 0.9 is actually useful on the 35mm, the 0.45 and IIIb are marginal, it's hard to say the Kenko is doing much at all.

Handheld? Let's put it this way, I've used a Silvestri H, which is about a 5 pound unit, handheld, with shift for several years. Really depends on having a steady hand and the right kind of viewfinder (the H's VF automatically adjusts to the camera's shift and has a bullseye level visible during use). On the Horseman, which is a non-shift designed to be used handheld, the best finder is the Leica Wideangle Finder M, which has framelines for 16-28mm (selectable) and its own bullseye level. The latter is probably the best viewfinder ever made for wideangle use with 6x9 cameras.

Dante

 

[Dan Fromm]

Dante, thanks for the reply. R'stock has recommended two CFs for Apo-Grandagons. + 2.5, withdrawn in favor of the newer +2. I have the old +2.5. Schneider's version of R'stock's +2 E67/86 is the IIIc. 0.45 and the IIIb are both + 1.5 and I'd have expected them to be marginal on Apo Grandagons, especially the 35 at the margins.

You're much steadier than I am. Funny thing is that I look at tiny preserved fishes at 50x, have to hand hold them so I can count their little teeth and have no problem with that. But holding a camera steady enough to keep framing has always been difficult for me. When I was shooting movies (S8, strictly amateur) I found that I had to shoot from tripod.

 

[dante]

Dan, the tradeoff is that I often drop things by accident, so six of one, half dozen of the other! Silvestri Hs and SW612s are made for handheld use; they don't have bellows or anything that makes them particularly high-maintenance for hand-holding.

I think they've fiddled around with the densities on these filters over time, or at least the designations. I'm sure if I threw one of them in a densitometer, I'd find out that the difference between a 2.5 and a 3 stop filter might be where the density is measured. Interestingly, someone told me that the glass in the Schneider IIIb and Heliopan 0.45 were the same. It looks to me like the Schneider has some kind of metallic sputter coating and the Heliopan is two pieces of cemented glass cut as a spherical shape and a spherical recess that add up to a flat filter.

I shot some 6x12 tests today at f/8 and 11 at 3m, 5m, and ∞ at an infinite subject, just to see if this phenomenon changes with further lens focus or wider apertures. I also did some tests in 6x9 of a ND 0.9 plus a 4x dark yellow filter. Let's just say that f/11, the required shutter speed was challenging, even with 400-speed film!

D