Friday, June 15, 2018

Back to basics: Kentmere 100 B&W Film

Contax AX 1.4/35, Coolscan 4000ED

Before I moved to Canada, I gave my darkroom equipment to someone and only brought the steel development tank and bulk film loader with me. Hope I may use them one day.
Ten years passed and digital technology rules the imaging world. B/W FILM photography becomes a niche market.  All Kodak B&W papers were gone.  Still remember the Kodak Elite paper? It is the highest Dmax paper at that time. Luckily B&W films and chemicals are still available widely but with much higher price.  Recently, Adorama had a promotion on Kentmere 100 bulk film so I brought one and try this out.

The Kentmere is a UK company which is under the management of Herman/Ilford. I am very familiar with Kodak films but not much on Kentmere.  So I need to start the test and see how its perform. I use Kodak D76 (stored in foil bag more than 7 years) and Kodak Fixer.  Using stock D76 solution for 9 minutes at 20C, agitating the film 10s per minute.  Fixing time is 6 minutes with fresh fixer solution.  The result is good and these time/developer dilution rate can be set as standard time. In future, tests can be conducted on pushing and contrast control.  Please be noted that the tank size and the way of agitation will yield different result.  Lesser agitation will cause lower contrast and vise versa.  So the above test is on 36 exposure film in 250cc tank. Please test the film by your own but 9 mins with stock D76 is a good starting point.

The Kentmere is a good contrast,  medium to low grain B/W film when using D76.  With traditional B/W film technology, it is a best value film.  The highlight has some compression (as Kodak Plus X).  If you need more wider and linear B/W film, you may try Tmax 100.
The base is a bit soft and so please take great care when using squeegee or sponge.

I have two film scanners. One is Sony UY-s90 for fast film scanning ( 8 min for one roll 36 exp film in 2000x3000pixels ). I use this for general film scan and if I need higher resolution I will use Nikon Coolscan 4000 which can provide 3764x5243pixels scanning.

Kentmere 100 is a good film for anyone want to start shooting film.  Investment is minimal and the films can preserve the images and your memories in the way you can touch with.

Secret:  Pierre water bottle is very good for B/W developer storage because of its colour

Highly recommend:  Ansel Adams The Negative

Thursday, March 01, 2018

Dual 704 turntable is......

Got a Dual 704 from a Tonearm designer and knowing that the turntable needed some special cares.  The turntable indeed was in a good shape especially the tonearm. Here is the list of problems.

1.  the motor -  need some help to make it start running sometime
2.  the tonearm rest is missing
3.  the nearly mint Grado FCE+1 missing the needle (by the way, I will change the head to Shure V15III as this moment)

After an hour of very pleasure chatting with the owner,  I brought the turntable back to home and started the restoration at once.

the heart of the EDS900 - four induction coils

704 has a 4-coil Hall Effect motor EDS900 as the driving unit. It is a very primitive motor in today standard.  However, the specification of this turntable is still very impressive. You can't hear any motor noise and feel no vibration at all. It seems that the workmanship is so good even the design is not modern.

Speeds: 33.33 and 45rpm
Platter: 1.2kg, 300mm, dynamically balanced
Wow and flutter: 0.05% WRMS
Rumble: Weighted less than 67dB / Unweighted less than 46 dB
Tonearm effective length: 222mm
Tangential tracking error: 0.16 degree/cm
Tonearm bearing friction: vertical less than 0.07mN /  horizontal less than 0.15mN
Tonearm:  Torsionally rigid tubular aluminum in low friction four points gimbal suspension, counterbalance with two mechanical anti-resonance filters

The jerky motor might be caused by the motor driver board.  The test show that the driver board is in perfect condition. So the motor itself should be the problem. The rotation was not smooth but the rotation rate is accurate. This symptom showing one or two of the coils in the motor was not working.  The scenario is just like a 4-cylinder engine with one dead cylinder.  The car can run but lack of power and is not running smooth.

The EDS 900 has four coils in total and you can see the picture of the internal.  The coils are glued on to the housing by epoxy.  Had a quick check on the connector and bingo! one of the connection to the coil was opened.  Look closer to the printed circuit board and two of the traces were corroded. Spent an hour to fix the circuit, lubricate the whole motor unit and also changed all the E-caps in the driver board. The turntable was now running at its should be.

The signal wires were also changed to Belden Teflon 83284 wire ( the capacitance of the original wire is 140pF and the new wire is about 90pF. it is a very important to know the value. The change of the capacitance will affect the frequency response. 83284 is a RG316 coaxial wire and even it is specified for high frequency use up to 3GHz but it also can be used for audio.)

The next thing to be tackled was the tonearm rest. Buying an arm rest is easy but why not to make one.  I still have some beech wood stocks so I took a small piece and sanded it to a desired shape. The best height of the rest is about 1.2cm with a 2.5cm sideboard which is used to prevent the overshot of the tonearm return. After soaking the finished wood parts in stain conditioner and then the stain, the arm rest was then polished with furniture wax.

All tasks have been done.  It is the time to sit down and listen music. 704 is a semi-automatic turntable. You need to place the head onto the record and set the needle down manually.  The needle is always in UP position when you put the head onto the record so it is fault-proofed.  The turntable will be automatically off when the head reaches the end. The head is now in the UP position again. When you put the head back to the arm rest the head will be in down position. Amazing simple but a very smart design.

The Vertical Tonearm Control allows the cartilage is in optimal playing position without using spacer in the headshell.

Finally here is the pic to show the coil connection with the resistance value.  If you found your 704 having a jerky motor, check it out first.


Friday, October 27, 2017

The classic Nikon Lens on Sony A7 - Nikkor 35mm f/2.5

It is a Nikonos 35mm lens.  And behind this lens it has a very interesting story.  The first generation of Nikonos indeed is not the invention from Nikon.  "Calypso" is the original name of this camera and Nikon took over the producti around 1960.  It was not right to let the Calypso using non-Nikon lens (Calyso uses SOM Berthiot and Angénieux lenses). So Nikon chose the w-nikkor 3.5cm f/2.5 which was used on Nikon SP camera. The latest version of w-nikkor 35mm (3.5cm) f/2.5 has multi-coating.

Using Nikonos 35mm on Sony A7 is simple. However, it is better to remove the front cover glass which causes "haze-like" and yellowish image.

It is a very good lens on Sony A7x camera and  better than the Contax T 38mm.

Pentax 50mm f/1.2 on Sony A7 - Can a 40 years old lens still survive in modern world?

Pentax 50mm at f/1.2 with Techart LM-EA7 on A7II
Is is a very best Double Gauss F/1.2 standard lens especially at 1.2.  Below is the report from a old German magazine. You can see how its perform and it has a better score than the Leica 50mm F/1 ! 


autgezeichnet - excellent
sehr gut - very good
gut - good
zufriedenstellend -satisfactory
weniger zufriedenstellend -less satisfactory
nicht zufriedenstellend - not satisfactory
sehr bedendich-Very concerned

autgezeichnet - excellent
sehr gut - very good
gut - good
zufriedenstellend -satisfactory
weniger zufriedenstellend -less satisfactory
nicht zufriedenstellend - not satisfactory
sehr bedendich-Very concerned

Gesamtwertung - total evaluation

unter 5000 Punkte - under 5000 point : sehr gut - very good
5000 bis 6000 Punkte: good
6000 bis 7000 Punkte: satisfactory
7000 bis 7500 punkte: knapp zufriedenstellend - just satisfactory
7500 bis 8000 Punkte: weniger zufriedenstellend -less satisfactory
über 8000 Punkte: nicht zufriedenstellend - not satisfactory
unter 5000 Punkte - under 5000 point : sehr gut - very good
5000 bis 6000 Punkte: good
6000 bis 7000 Punkte: satisfactory
7000 bis 7500 punkte: knapp zufriedenstellend - just satisfactory
7500 bis 8000 Punkte: weniger zufriedenstellend -less satisfactory
über 8000 Punkte: nicht zufriedenstellend - not satisfactory

You cannot compare this lens with the modern standard lens with million pieces of elements with aspherical surfaces having special low dispersal materials.  This lens has its own character and this lens had been sold for more than 20 years (with two different versions but have the same optical formula).  There is no prefect lens in the world but we should know their characteristics and make use of them.
Pentax 50mm f/1.2 is a lens for night. Even in a very strong back-lighting situation the lens is still having a very good performance.  The only drawback of this lens to me is the direction of focusing.


Monday, July 17, 2017

Contax T 38mm on SonyA7II Part II

I converted the Contax T 38mm lens into E-mount (using a metal 55mm cap and 55mm-to-E adapter in latest version, not the plastic cap) year ago.  It seems that it is better to plant the lens onto a LTM (Leica Thread Mount) so I can use this lens on my Techart Pro LM-EA7. it is not that difficult to make this modification and what you need to have are :

1.  33mm hole saw (a 1mm wider than the lens)
2.  LTM body cap
3.  Scotch Rubber Splicing Tape 23

It is a bit difficult to hold the cap when you drill the hole and here is trick.  Drill two smaller holes besides the holding bit hole and screw the cap onto a wooden board.  Using WD40 as lubricant when drilling the hole.

Fitting the lens onto the cap is straight forward.  Using Scotch rubber slicing tape and hot glue to set the lens position temporarily. Check the centering and focus.  Once ready use epoxy to fix the lens onto the cap.

Now I have the auto focus Contax Zeiss 2.8/38.   Here is some examples.

f/2.8 (no pro-process and click the image to see the actual )


 To see the different of the lens performance in 2.8 and 5.6 and it is not that difficult to see which is which

Friday, March 10, 2017

The legacy: Contax CY 70-210 f/3.5

This photo was taken in Italy twelve years ago and scanned from film.  CY 70-210mm is my most favourite zoom lens and so why I still have two.  It is heavy and weights 1.2kg. Being the first tele zoom lens Zeiss tried their best to build this lens. At that time, they did have the design of f/2.8 version but it was too big in size. They decided to have the 3.5 rather the 2.8 version. These are the only one of the two zoom lenses made in Zeiss, Germany for SLR camera.

The sharpness of this lens is very good and even across the field even though the resolution in the centre is not the highest. However, you will find that the corner resolution are kept the same as the centre .  I compared this lens  with the first generation Canon 70-200mm F/2.8.  Canon has higher centre resolution at 3.5 but lower on edge region when compare with Contax.  I sold my Canon and  stayed with the Contax.  Why?  Contax has better micro contrast and details in shadow.   Indeed the Canon is a very good lens and good for spot photography.

The closer together the sagittal and meridional lines are to each other, the smoother and more natural the background blurring (bokeh) becomes. It is one of the reason why I keep the Contax.  Please note that Contax's MTFs is measured from a real sample lens and the Canon's MTF charts are theoretical value.
Below is the MTF chart for Canon 70-200mm 2.8 II

It is a lens for film era but it can be used on digital.  However, I strongly suggest to use this lens with L41 UV filter and it can reduce the purple fringe issue on some digital cameras.By the way, any post image processor software can eliminate the purple fringe just by few clicks.

with Kodak SLR/c with no PP

Monday, March 06, 2017

Minolta m-rokkor 28mm: The lens I sold but bought back again.

This is a legendary lens from Minolta and it is the very best 28mm in Leica M mount.  However, this lens suffered the coating degradation in the first lens element.  This problem may caused by the anti-reflection black paint which leached out the chemical which attacked the coating.  I owned this lens before and it suffered a infamous white spot issue.  I sold it before it became too bad.

Last month I got a chance to buy a good copy of m-rokkor 28mm in reasonable price. The lens is pretty clean and has no visible white spot on the first element.  Just a bit haze but it is not enough to cause any issue. Previous owner might want to clean the lens by himself but he couldn't remove the nameplate and in the end he scratched it.  It gave a lesson to everyone and you should have proper tools and skills to service your lenses. If you don't have 100% sure what you are doing,  leave it as is or let someone to do it for you.

To prevent the further degradation of the lens coating, the lens should be cleaned but it is a bit tricky to take the first element out  There is no screw-in retaining ring to hold the front element, instead it was hold by lens clement and tight-fitted to the casing .  To loss the front element the ring should be removed by a coping saw with very very fine blade. (Google it you can find the procedure) or loss the clement by solvent. Then using a sucking cup to take the element out.  (And there is a small hole (air vent) behind the lens block and inserting a bamboo toothpick into the air vent can help to pop the element out). It is not a difficult process but it takes time to make it prefect.  The edge of the lens casing was smoothed out by #00 sandpaper and re-painted with solvent base matt black paint. If it was all done, the front lens block should look like new.

After re-lubricating all helicoids with lithium grease and cleaning the lens inside out, it is the time to test the lens. Let's go hiking.

The coating is really good, at least for this 38 years old lens
See the detail of the picture and resolution is pretty good (at f/4)
We cannot comment the colour accuracy by digital camera

All pictures were taken by Sony A7II with LM-EA7 Autofocus adapter. (Yes, it became an auto focus lens! ).  Aperture were set at f/4.  Corner performance is really good.  Please be noted that this lens is a retrofocus wide angle lens and not a traditional symmetrical lens design.  And it is the reason why this lens work so well with digital camera.

Friday, November 04, 2016

LS3/5A DIY Challenge Part 3

After the prototype,  here is the final version.  The changes includes
1.  Acoustic foam was used as original specification
2.  Smaller brass screw were used
3.  Matt black paint was applied as original specification (solvent base mat black paint)
4.  Better plywood stock and the thickness as original specification  (not from Homedepot)
5.  Oak veneer applied (original LS35A don't have this and very difficult to find a good Teak veneer)
6.  Better binding post

I am now waiting  for the coming of spring so I can start to build a 9L version cabinet according to the specification from Falcon Acoustic,.

The sound of this pair of speakers is so lovely and  it is better matching with tube amp as many people suggested.

My next project is to refurbish a pair of KEF Chorale (original) which have a bad cabinet and crossover.

Birch plywood from local wood mill
Steamed beech wood to make batten

Final touch - oak veneer

LS3/5A DIY Challenge Part 2

I choose brass screws and nuts (#10 for HF units/crossover stands/cabinet faceplate. #9 for LF unit) since they are non-magnetic and cause less problem when you assemble the cabinet where the very strong magnets are nearby. It doesn't mean it will sound better and yellowish colour of the screws are very match with the cabinet.

Original design of LS3/5A uses rubber gasket to seal the LF unit with the faceplate and the faceplate to the cabinet. I choose to use the cork sheet to serve these purposes.  I stick 1mm cork sheet to the back of the faceplate and it's not only seal all the air gaps but also reduce the reflection of the sound wave from the faceplate.

Work in progress

The most difficult part in making the cabinet is the countersink of the faceplate.  I need to tailor-make a circle guide for my router so I can make a perfect circle.

For the sake of convenience, I choose to use Pink Fiberglas Insulation as the acoustic material in cabinet.  It also doesn't mean it sounds better ether.  However, many people say, and indeed, fiberglass insulation is better. If you have the LS3/5A, you can try by yourself. May be one day I can find the wool insulation in Canada and try it out. It is the premium stuff for heritage house. 

Assembling the units are very straight forward except your metal tools will always stick to the big magnets. Just one suggestion, using tape to cover the spider of the LF unit before soldering the wire.  The hot solder will jump into the spider and melt the cone. Be careful.

First thing to do after the assembling is check the resistance of the output and make sure there is no short circuit.  Before any further measurement, I connect the LS3/5A to my Roberts amp (aka Akai M7) and listen to my favourite music. What a surprise!  The 7W little amp can actually handle the LS3/5A very very well. ...................
The soundtrack was a live recording and recorded by Tascam IM2 in my listening room.

The below is the measurement of the frequency responses between two speakers see if they are well matched.

And here is the comparison between Celestion SL6s and the DIY LS35A.  The peak in the graph is caused by the source (the test disc) and I may use my signal generator to test the speaker again in later time.