Petzvel projection lens observations.

**Tony Lakin** · 29-Sep-2008, 06:37

Hi
I recently purchased (on Ebay UK) five projection Petzvel type lenses, on checking each one on the ground glass of my 5X4 I observed that three of them were sharp in the centre and soft at the edges and two of them exhibited the swirls I have heard so much about, on further inspection I found that the rear lens element had been reversed on the two with the swirls so I reversed them so that they were in the proper Petzvel orientation and they then behaved just like the other three ie just soft, no swirls, do some petzvel lens have swirls when the lens elements are correctly located?

**Jim Galli** · 29-Sep-2008, 08:08

Originally Posted by Tony Lakin

Hi
I recently purchased (on Ebay UK) five projection Petzvel type lenses, on checking each one on the ground glass of my 5X4 I observed that three of them were sharp in the centre and soft at the edges and two of them exhibited the swirls I have heard so much about, on further inspection I found that the rear lens element had been reversed on the two with the swirls so I reversed them so that they were in the proper Petzvel orientation and they then behaved just like the other three ie just soft, no swirls, do some petzvel lens have swirls when the lens elements are correctly located?

Yes. Normally it's out in the edge area of the circle of illumination, and it's also at some distinct distance from a busy subject like tree limbs. ie. move in a bit and it seems to go away, and move out a bit and it does. So folk will find a suitable background, move around until it gets swirly, set up, then 'place' their sharp subject / person.