Tuesday, 4 August 2020

Lenses and ‘Glass Disease’

I was also told, in relation to microscopes, to be wary of using old lenses since over time the glass deteriorates. For photographic lenses, telescopes and binoculars that problem is seldom mentioned these days. The other problems that befall old lenses such as fungus, dust, separation of elements because of balsam deterioration, and condensation of lubricants as well as mechanical damage to the surfaces all get covered in guides to buying and repairing but actual deterioration of the glass itself is only rarely mentioned. I supposed the writers and repairers are often not dealing with really old lenses, merely ones that are not current models. For users and potential purchasers of old film cameras, particularly those made before the widespread adoption of coated lenses, binoculars, telescopes and microscopes, the problem can be real and insoluble.

The warning about using old lenses for microscopy came in what I can only describe as the most long-winded and boring course (apart from botany) it was my misfortune to attend. Robert Barer* was the new Professor of Anatomy in Sheffield and he gave his now infamous snail-pace course on the use of the microscope he had started at Oxford to those of us who were honours students in zoology. Before deserting most of the sessions, I did pick up that snippet on old lenses. In order to check my memory I bought a copy of his book, Lecture Notes on the Use of the Microscope, first published in 1953. There, he wrote:

Do microscope lenses deteriorate with age?
They may do so. The surfaces of some glasses tend to become cloudy with age, particularly in the presence of moisture. The balsam used to cement lenses together may dry up irregularly, or may retract, leaving an air space. Moulds sometimes grow in the space between lenses. Many old lenses are still perfectly good, but nevertheless caution is advised when purchasing any objective more than about twenty years old.

Since then I have seen a number of lenses affected by what is called ‘glass disease’ in lenses of all sorts. Glass Disease is a major problem in museum collections of glass objects. Its appearance depends on the chemical composition of the glass and the humidity of the surrounding air. It shows first as a cloudiness on the surface of the glass and soon becomes irreversible; the chemistry involved is explained in an article on Wikipedia. Because of the importance of chemical composition, some glasses show relatively rapid deterioration when in high humidity or submerged; others show no deterioration whatsoever.

The nature of glass disease was brought home to me during covid-lockdown. In 1964, my wife, before she achieved that status, spotted on old tip while cycling to work during the summer vacation. Investigating further, she found a number of old medicine bottles and the like. They were left uncleaned with her parents who simply moved the whole lot with them each time they moved house. They emerged when we cleared their house and were transferred to a shed in our garden. Re-emerging as the shed was tidied I was volunteered to clean them up. I have to say with due modesty that I did a very good job. Several, however, had large patches, inside and out, of surface cloudiness. That was resistant to every chemical treatment I could devise, from strong acid to organic solvent. In short they had glass disease and I read that the only way it could be removed was by gentle but prolonged mechanical abrasion.



A long-buried bottle with 'glass disease'


I have, over the years, seen examples of glass disease in microscope lenses, old binoculars and photographic lenses. Since high humidity is needed it is not surprising that fungal growth and glass disease sometimes go together, as in lenses kept without desiccant in the tropics. In the three years before he died my father acquired a large collection of classic cameras. Some of those had cloudy, uncleanable lens surfaces.

Regardless of chemical composition, the coatings applied to modern lenses prevent glass disease. Indeed I was surprised to read that they were invented for that purpose by Lord Raleigh in 1886. Only afterwards did he discover that they decreased the reflectivity and therefore increased the transmittance of light. Some coatings though peeled off in patches or were worn away by zealous cleaning, leaving the surface open to glass disease.


Difficult to see but this 1950s lens has signs of
cloudiness on the front surface

The only ‘remedy’ for lenses with glass disease I have seen is to polish them with jewellers’ rouge, a mild abrasive. The effect on the optical properties of the lens was not stated.

I, needless to say, avoid really old or decrepit lenses. They, like many of the cameras they were made for, are simply beyond redemption and are best relegated to the display shelf.

*Although he bored us rigid, we did have great respect and sympathy for him. Word had got out that he was the first to have entered the typhus-ridden Sandbostel Concentration Camp in April 1945; that experience affected him for the rest of his life. He was medical officer in the Guard’s Armoured Division in the advance across Europe. He was awarded the Military Cross for his actions, including rescuing the crews of three burning tanks while under accurate shellfire. Robert Barer (1916-1989) wrote One Young Man and Total War, Portland Press, 1998.

Tuesday, 19 May 2020

Sony AX-700 Camcorder: My bargain 1.45x Tele Extender—the Olympus TCON-14B

In the past I have often carried a 1.4 or 1.7x lens extender for whichever camcorder I have had at the time. That extra reach a lens extender gives can be very useful for mammals a long way away and for small mammals, birds and reptiles. Purist still photographers hate extenders because they degrade the image a little and sometimes a lot; they also reduce the maximum aperture. However, I have found them really useful for video and Sony used to make both tele and wide-angle adapters for its camcorders. They no longer do that. When I bought the Sony AX-700 last year I looked around for a suitable tele-extender. Most that have been made in the past have a much smaller diameter than the lens on the AX-700. But one doesn’t: the Olympus Tele Extension Lens Pro TCON-14B. This fits the 62 mm diameter screw fitting of the Sony without needing conversion rings. I soon found a range for sale at camera dealers and on eBay. I bought a mint one for £5.


The AX-700-TCON-14B combination






   

I had read old reviews which praised the optical quality of this Olympus lens which was built for an early digital camera, the E-10, a model first sold in 2000. I have found it to be the best tele extender I have ever used. Its only disadvantage is its weight of nearly half a kilogram; it really is solidly built.

The TCON-14B is a 1.45x extender which means I can achieve a 35 mm equivalent focal length of 505 mm using optical zoom only or 757 mm using clear image zoom. The values are with stabilisation turned off since I cannot imagine using the combination without a tripod. I normally output 4k footage to 1080 which means I can up to double the effective focal length in post production to over 1000 mm.

At short focal lengths there is vignetting, as with all tele extenders and so I only use it near or at the maximum focal length of the zoom lens.

The close focusing distance of 100 cm does not change with a tele extender and so it can be used for close-up shots when greater separation between subject and background is needed.

The front end of the extender has the slightly unusual 86 mm diameter filter thread.

The match between the diameter of the extender and the outside diameter of the camcorder lens is very close. The TCON-14B could have been designed for the AX-700 rather than for a camera 20 years ago.






Monday, 11 May 2020

One Tripod; Three Columns; Three Heads…and two types of mounting plate

Tripods are rarely a triumph of engineering design. Over the years I have owned or used many and even though I have a clear out once in a while, they still seem to accumulate as I try to find the perfect one for the job in hand. A major problem has been the attachment of heads; the torque from long lenses and telescopes has freed many a head from its mounting.

My go-to home and local, as opposed to travel tripod, is a Gitzo G1228LVL Levelling Mountaineer Reporter Mark 2. Although this one almost but not fully solves one of the key problems in tripod design—locking the head to the column by a bolt tightened from the underside of the ‘Power Disc”—changing heads then becomes a hassle, especially if I want to do a quick change. I have, therefore, searched for and bought on eBay as  many spare columns as I have been able to find: one full-length spare column and a shorter version. Therefore, when I want to change heads I just change columns. When the hook on the bottom of the column is not in place, that change takes seconds and even if I have the hook on, just a few seconds more.

The photograph below shows from left to right:

  • Manfrotto Junior Geared Head 410 on Gitzo Series 2 Column Kit D1228LVL.C or D1228C
  • 3-Legged Thing Eclipse Airhed Switch head on Gitzo Series 2 Ground Level Column Kit GS2511KB
  • Gitzo GH1720QR 2-way Birdwatching Head on Gitzo Series 2 Column Kit D1228LVL.C or D1228C (Used for telescope and video)





The other infuriating thing about tripods is of course plates: different sizes from different manufacturers and different sizes for different heads by the same manufacturer. At least for the heads shown, I can now have just two kinds of camera plate. I have converted a plate for the geared head to Arca Swiss (Andoer Mini Adjustable Clamp Quick Release Plate Compatible Arca Swiss QR 38 mm) so that two can be used with a simple Arca Swiss Plate. However, the Gitzo birdwatching head still needs its own plates (medium-long version permanently attached to the telescope; short version for video cameras). At least, two is better than three.




Sony FDR-AX700: Function Button Settings for Wildlife and Travel

As I have written before the ergonomics of Sony camcorders fall short. After trying my AX-700 in the field for wildlife and travel with unchanged function buttons, I started to make a series of changes which have made life more convenient for my particular purposes.

An annoying feature is that some of the function buttons are labelled with their default function, so that their label remains when the button does something entirely different. If I do not use the camera for several months or hand it to somebody else, it helps to be reminded of what the new function is. Therefore I used to a labelling machine to mark new or changed functions. The labels, of course, can be removed if necessary.

Because I sometimes want to take a still photograph and on this model a visit to the menu system is needed to shift from video to still and vice versa, I assigned Button 3 to toggle between the two modes. Then Button 4 becomes the shutter release (as labelled) in Stills Mode.

The normal Menu button is inconveniently placed way along the side of the camcorder. In Video Mode, therefore, I assigned Menu to Button 4, which is convenient for the index finger of the right hand.

I am often using the camcorder to take birds in bushes or trees. To check quickly if the autofocus is on the bird or surrounding branches, I have Button 5 set for Focus Peaking—also convenient for a finger of the right hand. I can then quickly decide whether or not to switch to manual focus.

I found I needed the option to swap quickly between focus areas so I have assigned Button 6 to Focus Area.

Buttons 1 and 2 remain unchanged.

Thus far, I find the modified set-up works well for the kind of work I do. Here is a summary:

ASSIGN BUTTON 3 SHOOTING MODE toggles VIdeo—Stills
ASSIGN BUTTON 4 MENU (video mode only)
ASSIGN BUTTON 5 PEAKING
ASSIGN BUTTON 6 FOCUS AREA

And here is the AX-700 with the Function Buttons labelled:








Wednesday, 19 February 2020

Sony AX-700. Great results but still a curate’s egg of a camcorder

Continuing my search for the perfect camcorder for wildlife and travel I bought a Sony AX-700. I should say at the outset that for wildlife, a camcorder is far more convenient to use handheld than a mirrorless camera. A camcorder is more compact, has a sufficiently long focal length lens for most purposes and can be held without shaking much more easily. I can speak from experience since I have both. But camcorders do not sell well and the few manufacturers bring out a new model very rarely.

I was looking for a camcorder with more reliable and defined-area autofocus than is available with the contrast only autofocus systems on Sony and Panasonic camcorders with a 1/2.5 in sensor, where the camera will often focus on what it can focus on rather than on what I want it to focus on, even when the object is in the centre of the viewfinder.

The Sony AX-700 has phase as well as contrast autofocus. The sensor is bigger (13.2 x 8.8 mm) than in my previous Sony and Panasonic camcorders (5.8 x 4.3  mm) but not so big that the depth-of-field at wide apertures and with the lens at full zoom is minute. It is the cheapest but most compact of the professional non-broadcast range of camcorders introduced by Sony in 2017 since it lacks the audio handle and microphone of those ‘higher’ in the range.

I have now had the opportunity to use the AX-700 at home and in Iceland.

The curate’s excellent parts of this curious egg of a camcorder are: the quality of video output and the autofocus which is truly outstanding whether using a wide autofocus area or a small central area. The increase in weight over the 1/2.5 inch camcorders is worth the trade-off.

But there are outstandingly bad features. The buttons, menu system and manual can only have been devised by somebody who has never had to use the results of his or her efforts. The menu is turned on by pressing a button under the lens on the side while controlling the selection by a joystick on the back panel alongside the start/stop button. The arrangement of the menu items is illogical and although the functions of the pre-labelled menu buttons can be changed there is often little advantage in doing so because for many functions, pressing one button is insufficient and the menu itself has to be brought up.

I defy anybody to understand setting up for slow-motion on first reading the manual. This is because it takes a while to realise that the camera does not record, say, 100 (120 in USA) frames per second, to the card, leaving the editor the choice of what to do in post-production. No, it stores footage taken at high frame rates and then records to the card the completed slo-mo video at 25 (30) fps—eventually since it takes time for this process to be completed and further shooting is impossible until that clip is produced.

Really annoying is the description of Super Slow Motion. I had to actually try the different settings using a falling pencil at my desk to see what the instruction manual is trying to say. And all that has to be done with manually set exposure and manual focus. 

Bob Myers of AVP Studios produced this excellent review of the AX-700 on Youtube. It is well worth watching and I will not repeat his criticisms here, other than to agree with them:





A number of difficulties seem to arise from the fact that for any of the ‘special’ features like slow-motion this is not a 4k camcorder. It is really a 1080 machine that will shoot 4k at 25(30)fps. But even at 1080 there are many features that cannot be used with autofocus and autoexposure. One might have thought that it would at its price shoot 4k at 50(60) fps but it doesn’t.

The AX-700 is probably over-priced and slightly over-heavy (although it will run for hours—no 30-minute limit) without overheating which suggests some of the weight is in heat-dissipating metal).

In conclusion, Sony’s AX-700 is not the perfect wildlife and travel camcorder. Many useful functions needed within seconds cannot be changed or accessed quickly enough. It is on the ergonomics where it falls short.

This camcorder then is typical Sony: some brilliant features let down by poor ergonomics, poor user interface and poor documentation. 

Tuesday, 21 May 2019

Panasonic HC-VXF1 Camcorder: How did it perform with wildlife in the field?

In my post of 28 August 2018 I explained how I my Sony AX53 had failed when nearly new and why I decided to replace it with the Panasonic HC-VXF1. I also pointed out how the Panasonic compared with the Sony in my hands.

I have now used the Panasonic for wildlife at sea and on land. I am just as impressed with it then as I was at the beginning, especially the arrangement and control of the menu system which is vastly superior to the Sony effort. In many ways it is the ideal travel camcorder.

The only area in which I have found it to be less good than the AX53 is the autofocus under certain and unpredictable conditions. Even in good light on occasion, the camera has not focused on the bird or mammal in the centre of the frame but has picked on a patch of ground further away. In one case, the focus point it picked was a patch of grass in good light, in another, the pebbles of a beach. I just could not get the camera to autofocus on a cicada sitting on a tree trunk; again it eventually settled on the background. My impression was that, although I obviously did not have an AX53 with me to compare, the Panasonic's contrast-detection AF was not quite so good as the Sony's, although the latter does not get it right every time.

Another user I know has found the same problem with even a large antelope in the centre of the frame being ignored and focus being established on the background well to the left or right.

The answer, some my remind me, is to switch to manual focus but speed is often of the essence. Birds and mammals may be in view for only a matter of seconds and by the time several buttons have been pressed and a ring turned, the opportunity may have gone.




My Sony AX700 which has phase and contrast detection autofocus on its larger sensor does not suffer the problem of the contrast-only autofocus camcorders. It is perhaps unlikely that on-sensor phase detectors can be installed on the tiny sensors installed in the camcorders at the lower end of the market. However, there is a trade off between weight and sensor size so I may well keep my Panasonic for those occasions when I do not wish to or cannot carry anything heavier.

Wednesday, 20 March 2019

Cameras: Why Not a Square Sensor?

Those of us brought up with the square format of 6 x 6 or 4 x 4 cm film can remember the delight of not having to move the camera. Printing to any size of paper (either landscape or portrait) was routine should the composition, or customer, demand it.

With modern sensors, the same number of pixels could be arranged as a square rather than as a 1.5:1 rectangle. The area of coverage on the film plane would be the same so there would be no question of having to have a difference in lens mount or focal length. The result would be as shown in the following diagram: a 29.4 x 29.4 mm sensor rather than a 36 x 24:


A Square vs a conventional Rectangular Frame Size
The red and blue frames have identical areas and therefore
the same number of pizels


Shock, horror may be your response—we would lose pixels along the horizontal. Yes, you would but not that many. My D810 would have 6011 x 6011 instead of 7360 x 4912, for example. But—shock horror—the camera would be bigger. Yes, it may have be be taller by 5.4 mm but it could be shorter horizontally by the same amount—and think of the ergonomic advantages whether hand held or mounted on a mono- or tripod.

The Micro Four-Thirds sensor goes some way towards a square format (1.3:1) but the manufacturers did not go the whole way.

Would I buy a ‘full-frame’ camera with a square sensor, smaller horizontally but larger vertically? Yes. Will one ever be manufactured? No chance. As I said, I never cease to be amazed by the ways of photographers still alive and well with the technological legacies of the 1950s.