Graflex.org

primus96 · Posted: Tue Dec 23, 2003 10:40 pm Post subject:

What diameter image circle does this lens give.
The site says it covers 4x5 but the zone of best sharpness doesnt really allow for movements.
That's how I interpret the comment on this site.

How many mm of coverage is desirable to allow for movements on 4x5?

Dan Fromm · Joined: 14 May 2001 Posts: 2144 Location: New Jersey

Nick · Joined: 16 Oct 2002 Posts: 494

t.r.sanford · Posted: Wed Dec 24, 2003 6:10 am Post subject:

If you measure the maximum rise and shift of the "Pacemaker" front, and assume the fall (provided by dropping the bed) is the same as the rise, you can draw a rectangle whose corners are the extreme positions that the center of the lens can occupy. My very rough measurements suggest that the diagonal of this rectangle is about 76mm.

The diagonal of the useful image projected onto a sheet of film in a cutfilm holder is about 153mm. As the earlier reply pointed out, a lens has to produce an image of acceptable quality across a circle of this diameter.

If you add to this the diagonal of the rectangle described by the maximum possible front movements, you find a requirement for an image circle about 230mm. in diameter, if you expect to use the full movements for a subject at infinity. A normal lens for a 5x7 camera, like the 8-1/2-in. "Ektar," ought to provide an ample image circle.

Back in the day, the "Speed Graphics" I came in contact with and used had 135mm. lenses. We knew that there were daring souls out there using 127mm. lenses and living on the edge. The general belief was that they'd be all right if they stuck with apertures of f:11 and smaller.

Dave · Joined: 05 Dec 2003 Posts: 78 Location: Canada

Me being the new guy here, I shouldn't butt in with my uninformed opinion, but here it is anyway.

(a) The image diagonal for 4 x 5 is about 16cm, so you need at least that image circle from a lens if you're shooting straight on.

(b) If you have a Pacemaker, at maximal rise and shift, you'll stretch the diagonal by about 2cm, so boost that up to 18cm.

(c) If you're tilting the lens standard, the image circle becomes an image ellipse at the film plane, so add maybe another 0.5cm.

Bottom line is that anything more than about 18.5cm of image circle is wasted on a Pacemaker series camera. If you ever see a good deal on something like a 135 Symmar (rare) or 150 Symmar (common), that would more than cover the limits of the camera.

Tessar type lenses (Zeiss Tessars, Ektars, Xenars) in the 127 - 135mm range make about 15.5 to 16cm of image circle, so you can barely use them on 4 x 5 if you can live with soft corners, which you'll probably crop anyway. These lenses were really optimal for quarter-plate cameras, but they were widely used on 4 x 5 with great success. (Think Joe Rosenthal at Iwo Jima.) Since you're in England, you've no doubt seen old MPPs around, many of which have 135 Xenars.

primus96 · Posted: Wed Dec 24, 2003 7:44 am Post subject:

If I were photographing a building of some sort and I didnt want converging verticals I would turn the camera upside down and utilise the bed drop as rise.
It seems that another lens would be a good idea if I am wanting to do this.
Anything in the 120-150mm range would do, as long as it gives around 200mm coverage.
As its for a Crown it has to be in a shutter.

Nick · Joined: 16 Oct 2002 Posts: 494

Dave · Joined: 05 Dec 2003 Posts: 78 Location: Canada

On 2003-12-24 04:59, Nick wrote:

primus96 · Posted: Sat Dec 27, 2003 7:19 am Post subject:

If the Ektar 127mm doesnt quite have enough coverage into the corners for 4x5 as suggested.
Say I did a full frame enlargement of a flat subject, how big could I blow up the neg before the corners started to look noticeably soft?
My usual lens testing method is to shoot a image of a brick wall and observe the sharpness of the bricks and mortar.
What aperture gives best performance/coverage?
I would say around f16 for definition.
Any thoughts?

Nick · Joined: 16 Oct 2002 Posts: 494

glennfromwy · Joined: 29 Nov 2001 Posts: 903 Location: S.W. Wyoming

The 127/4.7 Ektar is a Tessar type lens. All Tessars run out of sharpness before they run out of coverage. It's their nature. This lens performs best at f:11 or smaller. It will perform satisfactorily on 4X5 but it really shines on 2X3, where it uses only the sharpest part of the circle.
Press photographers prefered this lens on 4X5 because it is slightly wide angle. But then, they weren't out to produce fine art, either.

_________________
Glenn

"Wyoming - Where everybody is somebody else's weirdo"

primus96 · Posted: Thu Jan 15, 2004 12:13 pm Post subject:

The lens on my Graphic exhibits tiny pin point dots between the elements of the front cell. What's going on?
I was going to remove both lens cells & give the shutter a soak in Ronsonol.
I have another lens for it, a 150mm f4.5 Xenar badged 'Linhof' on the Compur shutter.

45PSS · Posted: Thu Jan 15, 2004 11:14 pm Post subject:

Examine the tiny pin point dots with a loupe.
Air bubbles are common and part of the manifacture process, they are not a problem. Small air bubbles will resemble pin point dots.
Lens element seperation is another possibility, it can be in the form of crystalization between cemented elements. It does not degrade the image quality unless very severe.
Fungus is the last possibility and is usually described as tree branch pattern. Fungus can damage the glass. It forms on the glass and the barrel of lens. If its faint, and you suspect fungus, clean all element surfaces and barrel surfaces with straight clorine bleach and cotton swab. Coat each surface with bleach socked cotton swab, let stand 5 minutes, rince with water, blot with soft cloth and air dry.
Clean lens elements when dry.
A recent post on Photo.net suggested a 1:1 mixture of hydrogen peroxide and ammonia in place of the bleach. UV light will kill fungus also but will not remove the stains.
Charles

_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

glennfromwy · Joined: 29 Nov 2001 Posts: 903 Location: S.W. Wyoming

Pinpoint dots could be interpreted as a lot of things, without actually seeing it. Examine the glass with a loupe while holding it up to oblique back light. It's possible that the dots are bubbles in the glass and under magnification, you should be able to see them as such. Another possibility is bubbles in the cement. Could just be dust or tiny paint flakes between the groups.
If it's bubbles in the glass, it won't hurt a thing. If it's bubbles in the cement (not likely) it probably would have little or no effect unless severe. The rest can be cleaned. Your 150 Xenar will provide better coverage than the 127 Ektar. They are both the same Tessar
design. Xenars were HIGHLY variable in quality, from excellent to rotten. If the lens was OEM on a Linhoff, it should be very good, as they hand picked them.

_________________
Glenn

"Wyoming - Where everybody is somebody else's weirdo"