Tuesday, 13 August 2013

Exakta Varex Cameras. 3: 2013 Perspective

It was nostalgic fun to have an Exakta (well three, actually) at the eye for a while again after an interlude of nearly 40 years. I bought three bodies which came with a total of five lenses from different eBay sellers.

It is very unfair to extend performance of an old camera to criticism of the manufacturer because so much depends on how it has been treated by its owner or succession of owners. So many cameras of the 1950s and 60s have been handed down to children who then abandoned them in attics, garages and sheds until moving house.

There were five problems with one or more of the bodies.

In all three (one Varex IIb and one IIa) the foam rubber that cushions the mirror had crumbled away or was in the final stages of doing so. That was easily replaced by material supplied by an eBay seller.

Replacement foam above the mirror

In both IIbs but not the IIa the frame counter was not working. It jumped all over the place when the film was advanced. This mechanical failure I am told is a common problem.

The frame counter did not work in the two Varex IIbs

The mirror was beyond use in the IIa. The silvering had deteriorated badly, starting it seems, from chemical reaction as the foam rubber broke up. The mirrors in the IIb were fine with just a little deterioration at the edges near the foam.

The mirror of a Varex IIa showing deterioration of the silvering

The major problem in the IIa but not the IIbs was the state of the shutter curtains. The deterioration of the material is a well-known problem. The curtains were wrinkled and had, when a light was held behind them, what seemed like pin holes. However, pin holes are usually a seller’s description. This is far a more serious condition. The whole (rubber?) material within the curtain is in process of breaking down and the light leaks are extensive, as the following photographs show.

Wrinkled shutter curtain - tell-tale sign of light leakage
Light coming through the shutter curtain

Light coming through the shutter curtain (LED torch in mirror box)
Smooth curtains not leaking light in a Varex IIb

Temporary (paint the curtain) and permanent (do-it-yourself curtain replacement or professional repair) solutions are shown in a number of websites. However, professional repair is an expensive route (£200 plus + VAT, I was quoted) which is why so many Exakta bodies are lying ‘beyond economic repair’.

I also tested the shutters of the two IIbs, both electronically, and with film. I did not test the IIa in view of the light leakage through the curtains.

One of the shutters tapered at 1/500th and 1/1000th sec so could not be used at those speeds without servicing. That shutter sounded better than the one in the second body which fired with a squawk that is said to indicate a lack of oil. The second was fine to use at all speeds. In terms of accuracy, the pattern was the same or similar to that reported in various websites. The higher speeds were slow: the slower speeds were fast.

Taking the IIb with the good shutter, from 1/500 to 1/60 sec (I could not get readings at 1/1000 with my set-up) there was 1 stop overexposure (to the nearest whole stop). From 1/30 to ½ sec timing was within ⅓ stop. At 1 sec there was 1 stop underexposure (i.e. the mean exposure of five firings was 0.54 sec instead of 1 sec).

In the body of the one of the IIb that tapered at high speeds, the variation was somewhat different. I held the sensor in a fixed central position in the film frame so that I was not looking at variation across the frame. 1/250 sec was near enough1/250 sec (mean 1/290). 1/60 and 1/30 sec were slow by one stop. ¼ and ⅛ were pretty well spot on while ½ and 1 sec were within 1/3rd stop of being accurate.

By knowing the accuracy of he shutter I was able to make appropriate corrections when I came to testing the lenses and actually using the better IIb to take a few photographs.

Rumour has it that the mechanical build quality of the IIa was better than the IIb. I cannot comment. All these cameras were in need of servicing. I doubt if any had been serviced since they were manufactured.

All the 50 mm lenses (two f/2.8 Tessars and two f/2 Pancolars) had problems. The pin that engages with the lever on the body had been torn out of one of the Tessars. I can only guess that somebody had inherited the camera and had then tried to change the lenses using brute force. The notched lever on the body was also bent (replacement found on a dead Exa). That lens was a write off and soon on its way to the recycling centre for glass and metal.

The other Tessar had slightly stiff focusing and some cloudiness on an inner element (what is the that cloudiness in chemical terms?) so contrast was low. In use it could still produce a reasonable image in high contrast conditions of bright sunlight.

One of the Pancolar was of the earlier design (without the automatic depth of field indicator lugs)(see 11 June post). Again it was slightly cloudy internally (again - what is that cloudiness?). It gave soft, low contrast results on film. The other Pancolar was of the later design with automatic depth of field indicators. Edge fungus was present but only affecting f/2 aperture. It was slightly cloudy internally and again produced soft, low contrast negatives.

In short the 50 mm lenses were way past their best. The Pancolar had the reputation of being fairly low contrast when new but my original 1960s Pancolar was capable of giving very sharp, punchy transparencies with Kodachrome.

Included with one of the outfits I bought was a 135 mm f/4 Sonnar. I was very impressed with the quality (so is its new owner). No sign of any cloudiness or fungus with just a few specks of something internally. The results on film were excellent - very sharp and excellent contrast. That lens had lasted well.

135 mm f/4 Zeiss Jena Sonnar

This Exakta lens hood fits all the 50 mm and the 135 mm f/4 lenses
Original Ihagee filters are not that common

The cameras did the job I wanted them for (to produce developed 35 mm for another project I will describe later) and have now gone to new owners.
So, after handling and using Exakta cameras again, would I like to turn the clock back and return to 35 mm film photography from full-frame digital? NO. NO. NO. We really have never had it so good. 35 film is in the past and offers no advantages over what we have now other than, for black-and-white, a stored silver image.

Friday, 9 August 2013

Zeiss Lenses: A Legend Destroyed

For those of us brought up from the cradle to believe that Zeiss lenses are the ultimate in optical design and quality, the review of a very wide range of f/1.4 50 mm lenses in Amateur Photographer (20 July 2013) destroyed that belief as a myth. At full aperture and even at two stops down, the resolution of the Zeiss Planar T* and the Makro-Planar T* (for Canon and Nikon bodies) was truly awful. Only at f/11 (yes f/11) was the resolution excellent. But who is going to buy an f/1.4 lens to obtain excellence at f/11? The lenses from Canon, Nikon, Pentax, Sigma and Sony were, overall, much better and (with the exception of the Sony Zeiss Planar) much cheaper than the very well-built Zeiss Planars.

No more shall I look at my Nikon lenses and think that Zeiss equivalents are probably even better. But, come to think of it, the evidence has been there for years. Nikon took off in the West because photojournalists covering the Vietnam war found Nikon lenses were incredibly sharp in the centre.

The German camera industry is not faring well in AP reviews this year. First the brickbats for the new Leica M and now quantitative evidence on the poor performance of Zeiss 50 mm lenses. Zeiss, of course, lost their leading position in the binocular/telescope market to Leica and, later, Swarovski.

AP, in giving its verdict, stated: …it is clearly an old optical design that has now been bettered. But then, curiously, that statement is hedged: However, the build quality is great, and for those who shoot street pictures, and manually focus, they are nice lenses. Even more curiously, AP gave these lenses 4 out of 5 stars (no lens scored lower than a 4). By my reckoning, they were 1-star. Judging by the quantitative data, being excellent at f/11 with a high price does not make up for the fact that they were poor lenses compared with all the others. My Nikkors can rest easy.

Sunday, 4 August 2013

Cameras for Birding: The ‘Bridge’ Camera Zoom War: Panasonic Lumix FZ72 Joins The Fray

Panasonic have now joined the zoom war in the increasingly popular superzoom ‘bridge’ camera category that is so good for birding.

I have added this camera to the table I prepared for my post of 9 March 2013. These are the key features as far as using the camera for birding are concerned but it would be good to know how it handles noise at high gain (ISO setting) and the chracteristics of its autofocus.

Nikon P520Canon SX50Fuji HS50Sony HX300Panasonic FZ72
Optical Zoom (equiv)24-100024-120024-100024-120020-1200
Max Aperture3-5.93.4-6.52.8-5.62.8-6.32.8-5.9
Sensor Size1/2.31/2.31/21/2.31/2.3
Resolution (Mpixels)18.112.11620.416.1
Output Size (pixels)4896x36124000x30004609x34565184x38884608x3456
VideoFull HDFull HDFull HDFull HDFull HD
Weight g550595758623562

I haven’t seen a review of this new camera yet but how the market has changed in little over a year: from only a Nikon to a five superzooms from all the main manufacturers. Given the reputation of the Lumix series, I suspect this new one will provide the others with stiff competition.

Thursday, 1 August 2013

Video: Camcorder, Compact or DSLR? It all depends on the depth of field you want

The useful article The Definitive Camera Guide in the new magazine, Digital FilmMaker, together with a discussion in Amateur Photographer on whether to buy separate video and still cameras, prompted me to remind myself, in the headlong rush to use full-frame and APS-sized cameras for video, why a small sensor, as found in most amateur, 'prosumer' and some professional camcorders, is preferable for the type of video photography that I do – travel, wildlife and documentary. Film makers which I define as those setting out to make a movie with actors or a staged documentary, appear to be fixated on getting a film-like appearance. Since the appearance of film can be more easily achieved with the depth of field range of a larger sensor (as with 35 mm cine cameras) some follow the fashion and use a large-sensored DSLR. The fact that we see in such videos endless focus shifts that the dramatic effect is expected and therefore ruined is neither here nor there. Such is the world of arty film making.

For travel, wildlife, family and documentary videos there is one great disadvantage in using a DSLR for video. The depth of field is simply too shallow. I have seen some awful efforts. Even if the camera can be focused, the slightest movements lead to the autofocus hunting to regain focus; objects slightly in front or slightly behind the point of focus that are needed to be sharp to provide context are fuzzy. DSLR video is fine for controlled shooting. The many rigs now available can be used; focus can be pulled manually after rehearsing the shot.

Camcorders are not thought cool any more. But they do work and work very well, especially those in the prosumer ranges of the major manufacturers (even though the gimmicks, like the projectors now added by Sony for example are a real pain and very silly). The quality of the full HD video is superb. I have sold wildlife footage from my Sony camcorder.

So what is the advantage of using a small sensor for video? For stills, the bigger the sensor the better, particularly for the prevention of noise. The advantages of a smaller sensor in terms of depth of field are very great for travel and wildlife. In general, with the same final image size, depth of field increases inversely to the size of the format. That is because for the same picture size, a shorter focal length lens can be used with the smaller format. Shorter focal length equals greater depth of filed. Even though the circle of confusion has to be reduced as the format size decreases, the depth of field is still increased.

The first graph illustrates the point. I compare five formats: 1. Full-frame 35 mm; 2. APS (I know the various sensors vary in size a bit but I have taken one for comparison); 4/3 format as used on many modern non-DSLR cameras; 2/3 sensor as used on many professional camcorders; 1/2.88 sensor as used on many amateur, prosumer and some professional camcorders. I calculated for each the equivalent focal length of the lens and, using the circle of confusion appropriate to each format, read off the hyperfocal distance at f/11 and f/4. The graph shows the near point of acceptable focus (i.e. half the hyperfocal distance), the far point of course being infinity.

The difference in depth of field is clear and dramatic. At a small aperture and at focal lengths shorter than the equivalent of about 50 mm, it is difficult to be out of focus using a camera with a small sensor.

I used the same data to calculate the depth of field with the camera focused at 3 metres, again at f/11 and f/4.

It can be seen clearly why footage from a small-sensored iPhone (1/3.2 – similar to 1/2.88) often produces better results in casual photography than a DSLR.

These calculations were all for the equivalent of a 50 mm lens. At 200 mm the effects are even more marked. Imagine a subject moving (e.g. a child playing or a group of otters) in the frame of full-frame DSLR where the depth of field is only a total of 14 cm at f/11 compared with a camcorder with a depth-of field of 100 cm.

Shallower depth of field can be obtained with a small sensor (even if not to the extent possible with a large sensor) by using neutral-density filters (built-in in some professional camcorders) or a polarising filter.