lunedì 15 dicembre 2014

Dompilan diaphragm repair

Meyer Optik Görlitz Domiplan was a quite nice 50m/f 2.8 compact and standard lens common in Exakta (especially for the Exa) and M42 (Praktica) mount.

I have two and both of them suffer from a sticky diaphragm (iris aperture) syndrome, like most of old lenses.

I read horror stories about this lens, people ruining it completely, declaring it unrepairable or so. I don't think it is any harder than other lenses I tried to repair, provided it is just stuck and not broken. When it gets stuck, the blades gum up very hard so trying to force it may cause the pin and leverages to break.

I find the lens quality quite nice, for being a triplet! Smooth colors, bokeh and only slight vignetting. I disagree with people calling this a bottle bottom glass or "Holga like"! I think people having bad experiences had badly serviced or broken lenses. See the examples below.

Start by removing the back-part, the bayonet. Then you can remove the barrel holding the lens. You do not need to remove the lens itself. Three screws and you get the parts seen in the picture below.

Remove all the blades carefully, put them on a paper towel.

Clean the blades with petrol, light gas, lighter fluid, what you prefer. They are made out of steel, be careful not to knick them and not to damage their drive pins.

If you had a serious oil problem, then the lens surfaces might be hazy and you need to clean those too.

The blades need to be inserted one over the other, like a spiral stair case. The most difficult are the last and the butlast, because the nose needs to go "below" the first, it can be seen well in the picture below.
Try not to touch the blades with greasy fingers. Once all blades are in, you need to slightly close them before putting the cover ring and screwing it down. To do that, gently actuate the leverage, as shown in the following picture. The three screw both fix the upper part to the ddiaphragmring, but also fix the whole assembly to the lens barre.

Once closed and screwed down, the actuator lever should already work smoothly. Don't close it too much or it will stick.

Remount the rest of the lens with care. Take care of the two opposed springs that go into the barrel. Take care that the f-stop-ring is aligned properly.
The Exakta version is easy to remount, the M42 version has a different linkage to the bin, be sure to mount it in the correct open position!

Once everything is reassembled, use the lens! In my experience it is a light, compact lens which works fine with color and b&w films. It works best around 8-11, but 5.6 is already quite fine. Of course at 2.8 it vignettes a bit, but it remains reasonably sharp in the middle,

Here a photo taken with my Exa and the Domiplan:

Here again, wide-open at 2.8:

domenica 24 agosto 2014

Canon AE-1 shutter repair

My Canon AE-1 suddenly did not expose at all: all shutter times "sounded" the same: a check showed the shutter was not opening at all, even "B".

There are several forum posts on the internet which report "magnet" problems usually related to random malfunction or to the camera firing while loading and they show you how to clean an electro-magnet.

My problem was different, but I decided to take a closer look.

The Canon AE-1 has two electro-magnets, one for the first curtain and on e for the second curtain.
If the first curtain is not correctly retained, the camera will fire too early or other problems I can only imagine. If the second curtain is not retained, there is no time delay and the camera makes the shortest possible time. It is not even 1/1000", in my case it was black, the second curtain catches up the first and the shutter is dark. It is the bigger magnet, protected by a plastic case.

Cleaning the second-curtain electro-magnet is easy; nothing to open, just gently sweep it off with alcohol without damaging the wires and solders. This magnet has no protection at all and evidently can get dirty easier.

Once cleaned, by trusty canon worked flawlessly again!

It is worth checking that the coils are still fine. In my case the first curtain electro-magnet had an in-circuit resistance of about 100 Ohm. The second curtain magnet has an in-circuit resistance of about 200 Ohm instead.

First curtain magnet

Second curtain magnet

domenica 29 giugno 2014

SuperPan 200, Stand development

During the Carnival in Venice I used Rollei's SuperPan 200 as 35mm, as 6x6 and 6x9 in my two folding cameras.

I developed the Superpan 200 in Rodinal  1+150 1h30, full stand after initial 20" agitation.

The combination appears to work very well, I got full-range negatives both sun situation, as complete overcast.

An example showing the excellent bokeh of the mythical Heliar, wide open:

venerdì 10 gennaio 2014

Rollei ATP Stand

Rollei ATP. Rated 25/15° ISO - Development, 1+120 Rodinal, 30" initial agitation, 1h30 full-stand development.

Late Autumn light, San Giovanni Bianco.
Leicaflex SL, Summicron 50/2 Germany

The film has an astonishing detail, the development is still slightly harsh in the lights which makes scanning difficult.

Technical details come out very well too. The film is so sharp, that micro-blur because of hand-held shooting becomes easily apparent. However, using fast lenses, during daytime you can use the film without problems.

Here the flat-four opposite piston Lycoming engine of a Robin helicopter.