Pentacon 30mm f/3.5 M42 lens on Sony Nex

This is a brief review of the Pentacon 30mm f/3.5 prime lens fitted with an M42 screw thread lens fitted to my Sony Nex 6 camera.

I bought this lens from E-Bay UK for £7 as a ‘sold as seen’ lens because it had some internal dust. Since lens of this vintage are normally reasonably easy to take apart I thought it was worth while trying it out to see what sort of performance I could get with my Nex 6. A 30mm lens would be about 45mm equivalent taking the Nex crop factor into account so this is a useful general purpose lens.

The lens is about an inch and a half high, and covers the range f/3.5 to f/22. The aperture is pre-set, which means that there is a ring to set the aperture and another ring which sets the limit of the maximum aperture. This was used before automatic diaphragm control, so the photographer could set the aperture limit with the pre-set ring (once the aperture was worked out using a light-meter), and then set the lens to maximum aperture for focusing knowing that he just needed to stop it down to the limit when taking the picture. There is a small amount of damage to the bottom element mount, but this looks like it is where someone has tried to remove the element without the proper tool and isn’t going to affect the pictures obtained.

When I received it I found the lens was pretty straight forward to take apart, at least from the point of view of the front elements. There are two tiny holes next to the main front element which allow a lens spanner to fit and the whole front element then rotates out of the lens. Once removed, a small screw needs to be removed to allow the glass elements themselves to be removed and cleaned. I did this and got as much of the internal dust out as possible and then simply re-assembled the unit the same way it came apart. Careful examination revealed that although I got most of the dust out there are various marks on the glass element which are still there. I don’t believe this is fungus, but I’m not completely sure what fungus looks like so I’m going to try again with a solvent to see if it comes off.

Other than the internal dust the lens was in good condition for it’s age. There are almost no marks externally and the focus and aperture rings move smoothly. The lens is of a pre-set aperture design with no click stops so it would be particularly useful for video use, although at a max aperture of f/3.5 it’s not particularly fast.

Example files

These are some example pictures I took around Stevenage today with this lens fitted to my Nex 6 (to view the pictures full size use this link and navigate with the keyboard arrow keys or click each picture for the next). I make no claims for their artistic merits – I’ve taken so many pictures around Stevenage over the last 4 or so years that there is almost no area I haven’t pointed a camera at. As sample images however you can draw your own conclusions about the performance of the lens. I don’t think it is up to the standards of the Takumar 28mm f/3.5 for colour, contrast or sharpness but it’s a reasonable buy for £7. Please compare this with the Meyer-Optil Lydith, which is a very similar lens.

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