240mm Graphic Kowa on ULF - images from the corner (a.k.a. coverage).

[Lachlan 717]

Forget coverage charts; here's photographic documentation of corner detail on a 7x17" camera.

This was a circa 2 minute exposure @f64. Ilford HP5+ dev in Tetenal Ultrafin. Korona 7x17 camera on Manfrotto 161MkII tripod.

The lens is a Graphic Kowa 240mm f9 in barrel.

Please not that I scanned the corner images through the clear neg holder (thus the lines through the image).

These scans have not been touched - direct from the scanner (thus, a bit dark).

I've included a low res copy of the whole image with reference to where the sections were taken from.

I hope that this settles, once and for all, that this lens does cover 7x17" (and, therefore, 11x14") with good sharpness in the corners.

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[karl french]

Yes, it's amazing on 7x17 (and 10x12.) I'm going to try it on 8x20 this weekend.

[Corran]

I'm going to try it on 8x20 this weekend.

Looking forward to your results!

Thanks for posting Lachlan.

[Dan Fromm]

Lachlan, thanks very much for posting. Two questions and a comment.

What was the film plane (or lens or anything near the camera) to subject distance?

Where's the illumination falloff? I ask because at infinity with a 240 mm lens 7x17's corners are ~ 2 stops down from the center. I understand that negative film is very forgiving but still ...

We have very different sharpness criteria. With my monitor and to my eye, viewed from ~16" images 2, 3 and 4 seem pretty soft. I don't know whether the softness I see is due to the lens or to wind. My monitor, my vision and your scanner are also possible culprits. I suspect the lens 'cos diffraction limited resolution on-axis is ~ 24 lp/mm at very low contrast and resolution off-axis is worse.

Thanks again, cheers,

Dan

[Michael Kadillak]

I have used my 240mm Computar f9 lens on 11x14 and have never had an issue with coverage. Similarly, my 305 mm Computer covers 8x20 with room to spare. My only issue with the 305m Computer is circular curvature when shooting vertical architecture at the edges of the format. Having attempted to communicate with the manufacturers of the Computer lenses, it was clear to me that a considerable volume of meaningful data on the Kowa and Computar series of lens manufacturing remains unknown. In this case I would revert to factual visual results as above.

[karl french]

Dan,

I think there is definitely some motion in the ferns. Otherwise, I think the scans are quite sharp. The 240 GK is really very sharp for contact printing on 7x17. I have some shots from Zabriskie Point with the 240 on 7x17 that I'll post. Scanned with an Epson 4990.

[Lachlan 717]

Also, as noted, these were scanned through the neg sleeve.

And at low res.

As for drop-off? All I can say is that it is what it is.

I'll post the whole (half-frame) 7x17" scan later.

[ic-racer]

Nice image. Thanks for sharing.

[Dan Fromm]

Lachlan, a question of fact. Are the ferns in image #2 (tree trunk and ferns) the same type as in image #3? I ask because #2's ferns have fronds leaflets that are somewhat resolved and that show what I think is motion blur while #3's have fronds with no leaflets discernible.

[Greg]

Is the 240mm f/9 Graphic Kowa and the 240mm f/9 Computar the same lens but just labeled differently?

[Lachlan 717]

Lachlan, a question of fact. Are the ferns in image #2 (tree trunk and ferns) the same type as in image #3? I ask because #2's ferns have fronds leaflets that are somewhat resolved and that show what I think is motion blur while #3's have fronds with no leaflets discernible.

I suspect different. The bigger (distant) ones are a species of Dicksonia, I believe.

[Lachlan 717]

Is the 240mm f/9 Graphic Kowa and the 240mm f/9 Computar the same lens but just labeled differently?

Some say yes; some say no.

I say that I think there are some that are, and some that aren't!!!

[Michael Jones]

Some say yes; some say no.

I say that I think there are some that are, and some that aren't!!!

Try this from Gordon Hutchings: Many years ago,
Burleigh-Brooks introduced a line of lenses under the name of Computar; the
Kowa Lens Company of Japan made them. These lenses were a remarkable value
as they were a wide-angle plasmat, excellent quality and quite inexpensive.

After Burleigh Brooks folded, the lenses were briefly carried by Kyvyx and
were called Kyvytar and then independently offered by Kowa a Kowa Graphic
lenses, in both shutter and barrel. These lenses were offered in 150, 210,
and 300 mm length and are excellent buys, if you can find them. These lenses
are hard to find, especially in 210 mm length. The cell of 150 and 310 mm
barrel mounts will screw directly into a Copal # 1 shutter, with no adapters
required. Some times the barrel lens will come with thin spacers. The trick
is this, for center image use, the more spacers between the rear cell and
the shutter the better. For the corners of the image, no spacer is best.


This is why, in a shutter mount, we often see one spacer as the best overall
compromise. For comparison, the 150 mm Kowa has an image circle of 290 mm or
about 1degree inches of movement for a 5 x 7. The 210 mm Kowa has an image
circle of 460 mm of about 2 degree inches of movement for the 8 x 10. This
is why we love these lenses so much"

and go here:

http://www.largeformatphotography.info/forum/showthread.php?10255-The-Computar-lens-and-ULF-coverage


Mike

[EdC]

So, to sum up for those of us not as well versed in the history of these lenses, there will be some 240mm Kowa lenses that will adequately cover 7x17, but others that will not. Given that, it seems that it is up to the buyer to exercise a good deal of caution if ULF coverage is needed. I see that a near new Graphic Kowa 240mm is available now on another site, but I'm concerned about whether that lens will be one that actually will properly cover 7x17.

If I've overlooked anything, please fill me in.

Thanks,

Ed