kodachrome25
Member
Have recently been been addressing some internal issues on two Canon 7 bodies.
I re-calibrated the rangefinders for infinity and one meter distances. 1st adjustment was the vertical alignment via screw near shutter speed dial spindle, 2nd adjustment was the horizontal alignment via screw next to viewfinder window and 3rd adjustment the near distance alignment via the hard to reach hexagonal eccentric above the rangefinder roller. I fabricated two (one straight, one angled) thin 6mm open jaw spanners using as a guide the tool illustrations at the back of the Canon 7 service manual. These were filed out of Meccano contruction kit struts which were thin enough to fit between the roller and roller arm. The rangefinder patch contrast was effectively improved by sticking a small rectangle of amber colored gel (cut from a variable contrast printng filter) behind the rangefinder window inside the top cover. This made focussing far more positive even in low light.
The next issue was frameline accuracy at close distances as the framelines move to compensate for parallax. I focussed the camera fitted with 85mm lens on a flat vertical surface and viewed it through a ground glass in the film plane with shutter setting at T, then marked with strips of black tape the edges of the view through the lens. Comparing this view with the framelines through the viewfinder it is apparent that the area captured on film is noticeably smaller than the framelines indicate and not qiute centred, ie the framelines show more above the subject compared to the groundglass view. The framelines are only an estimate (particularly with longer focal length lenses) of the view recorded on film. This could be that Canon set the frameline accuracy to coincide with the view at infinity as opposed to the Leica set distances of one or two meters depending on camera model. This discrepancy is far less noticeable when using short focal length lenses such as wide angles. In some cases looser framing when looking through the viewfinder will avoid cutting off important elements at the edges of the picture.
On one camera body the framelines were ragged and indistinct. The frameline mask is a 15x11mm piece of glass printed with the outlines for each lens focal length with some kind of black ink or paint (the clear areas of glass being the actual frames) and in this case was flaking off due to ageing or fungus affecting the glass surface. I repaired this by spotting in the damaged areas with a very fine tipped permanent black marker pen under a magnifying glass, rather like retouching old glass negatives. Only going close to the frameline edges on the unprinted side of the glass so any mistakes could be wiped away with IPA solvent. The result was acceptable.
Again on one camera body the selenium meter was not working, so I checked that voltage was coming from the photoelectric cell by attaching jump leads between the meter contacts and top cover to earth. This arrangement showed a swing on the meter needle and the conclusion that there was poor contact between the metal tag protruding from the galvanometer top and the pin connected to the meter hi/lo switch. Cleaning those parts and bending the metal tag slightly upwards brought the meter back into operation. It also tested accurate when compared to a Weston Master selenium meter, which I use as a benchmark for all meters. Selenium photoelectric exposure meters are often regarded as non working when a simple cleaning of corrosion or oxidation from contact points are an easy remedy.
I re-calibrated the rangefinders for infinity and one meter distances. 1st adjustment was the vertical alignment via screw near shutter speed dial spindle, 2nd adjustment was the horizontal alignment via screw next to viewfinder window and 3rd adjustment the near distance alignment via the hard to reach hexagonal eccentric above the rangefinder roller. I fabricated two (one straight, one angled) thin 6mm open jaw spanners using as a guide the tool illustrations at the back of the Canon 7 service manual. These were filed out of Meccano contruction kit struts which were thin enough to fit between the roller and roller arm. The rangefinder patch contrast was effectively improved by sticking a small rectangle of amber colored gel (cut from a variable contrast printng filter) behind the rangefinder window inside the top cover. This made focussing far more positive even in low light.
The next issue was frameline accuracy at close distances as the framelines move to compensate for parallax. I focussed the camera fitted with 85mm lens on a flat vertical surface and viewed it through a ground glass in the film plane with shutter setting at T, then marked with strips of black tape the edges of the view through the lens. Comparing this view with the framelines through the viewfinder it is apparent that the area captured on film is noticeably smaller than the framelines indicate and not qiute centred, ie the framelines show more above the subject compared to the groundglass view. The framelines are only an estimate (particularly with longer focal length lenses) of the view recorded on film. This could be that Canon set the frameline accuracy to coincide with the view at infinity as opposed to the Leica set distances of one or two meters depending on camera model. This discrepancy is far less noticeable when using short focal length lenses such as wide angles. In some cases looser framing when looking through the viewfinder will avoid cutting off important elements at the edges of the picture.
On one camera body the framelines were ragged and indistinct. The frameline mask is a 15x11mm piece of glass printed with the outlines for each lens focal length with some kind of black ink or paint (the clear areas of glass being the actual frames) and in this case was flaking off due to ageing or fungus affecting the glass surface. I repaired this by spotting in the damaged areas with a very fine tipped permanent black marker pen under a magnifying glass, rather like retouching old glass negatives. Only going close to the frameline edges on the unprinted side of the glass so any mistakes could be wiped away with IPA solvent. The result was acceptable.
Again on one camera body the selenium meter was not working, so I checked that voltage was coming from the photoelectric cell by attaching jump leads between the meter contacts and top cover to earth. This arrangement showed a swing on the meter needle and the conclusion that there was poor contact between the metal tag protruding from the galvanometer top and the pin connected to the meter hi/lo switch. Cleaning those parts and bending the metal tag slightly upwards brought the meter back into operation. It also tested accurate when compared to a Weston Master selenium meter, which I use as a benchmark for all meters. Selenium photoelectric exposure meters are often regarded as non working when a simple cleaning of corrosion or oxidation from contact points are an easy remedy.