The Imagon 200 5.8 for 4x5?

[Jac@stafford.net]

An opinion: We need an Imagon focal length long enough to encourage aberrations intended by Rodenstock for particular formats and in that regard a focal length longer than just enough to 'cover' a format is necessary.

Aside: Does anyone have an idea of why many Imagons are offered with missing sieves? Where do they go?

[Bob Salomon]

An opinion: We need an Imagon focal length long enough to encourage aberrations intended by Rodenstock for particular formats and in that regard a focal length longer than just enough to 'cover' a format is necessary.

Aside: Does anyone have an idea of why many Imagons are offered with missing sieves? Where do they go?

Once the user decided which gave the needed result most of the non used ones were probably misplaced and lost.

[Ed Vatza]

I just found a reference chart that specifies the image circle of the Imagon 200 5.8 is 150 at 11.5. So at 7.7 the image circle would be smaller. Correct? And if one uses a Copal 3 shutter and shoots at f/22 or f/45 for example, the image circle would be larger but i lose some of the softness. I'm new to this stuff and just trying to get everything straight in my old brain. I do understand that the 200 may not be the best alternative for me for landscapes but still trying to figure this all out..

Ed

[cowanw]

At f22 or F45 you will be at a smaller aperture than the centre hole on the discs and so not benefiting from having a disc at all. I.E. you lose, not some, but
all of the softness.

[Bob Salomon]

I just found a reference chart that specifies the image circle of the Imagon 200 5.8 is 150 at 11.5. So at 7.7 the image circle would be smaller. Correct? And if one uses a Copal 3 shutter and shoots at f/22 or f/45 for example, the image circle would be larger but i lose some of the softness. I'm new to this stuff and just trying to get everything straight in my old brain. I do understand that the 200 may not be the best alternative for me for landscapes but still trying to figure this all out..

Ed

An Imagon basically has 2 different focal lengths. The center is different from the edges. That is why the Imagon effect is controlled by the disks.

Each disk has a different size center hole and the small holes around the center hole can be opened and closed to control how much of the periphery light strikes the image plane.

If you use the diaphragm in the shutter you block the periphery rays and lose the effect of the Imagon. That is why the instructions state that the exposure is controlled by the disks and not by the aperture in the shutter which should be left wide open.

It’s your choice but if you want an Imagon then you probably want what an Imagon can do. That means disks only, no umbrellas or soft boxes and a 5:1 lighting ratio, or greater for proper halation!

[Jac@stafford.net]

if one uses a Copal 3 shutter and shoots at f/22 or f/45 for example

Rodenstock's using a shutter with an adjustable aperture control was a big mistake from day-one. Best forget it is even there.

[Ed Vatza]

Rodenstock's using a shutter with an adjustable aperture control was a big mistake from day-one. Best forget it is even there.

Question: Of course I am looking for the Imagon effect and that requires the disks. But without the disks, doesn't the lens work like any other 200mm lens? You can shoot wide open at f/5.8 or stop down as far as it goes. Right? You'd be looking for sharp results as opposed to soft results.

Ed

[Louis Pacilla]

Question: Of course I am looking for the Imagon effect and that requires the disks. But without the disks, doesn't the lens work like any other 200mm lens? You can shoot wide open at f/5.8 or stop down as far as it goes. Right? You'd be looking for sharp results as opposed to soft results.

Ed

Yes Ed it will. For some unknown or know reason a few around here just push the myth that the Imagon can only used w/ the disc. This has been disproven by many others. It works like any under corrected wide aperture achromatic pair that diffusion will sharpen up as you stop down.



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[Bob Salomon]

Question: Of course I am looking for the Imagon effect and that requires the disks. But without the disks, doesn't the lens work like any other 200mm lens? You can shoot wide open at f/5.8 or stop down as far as it goes. Right? You'd be looking for sharp results as opposed to soft results.

Ed

Without a disk it is a very soft image with maximum halation.

Stopping down the shutter’s aperture totally changes the effect.

[Jac@stafford.net]

Question: Of course I am looking for the Imagon effect and that requires the disks. But without the disks, doesn't the lens work like any other 200mm lens? You can shoot wide open at f/5.8 or stop down as far as it goes. Right? You'd be looking for sharp results as opposed to soft results.

Without the discs, shot wide open it is definitely wonky. Stopping down with no discs sharpens more as you progress but it's still not like a conventional lens.