Wednesday, 26 March 2008

Using Epson flatbed scanners for densitometery

In his book "Beyond the Zone system" Phil Davis outlines how to adapt a pentax spot meter to be used as a make shift densitometer (for checking negative density in understanding development and traditional enlarger printing). Well, if that can be done (and calibrated) why not use a scanner with a known (and constant) light soruce which already seems to be calibrated. I this article I explore using my Epson in just that way.

Two of the scanners I use for film scanning are Epson scanners (a 3200 and a 4870). These are not exactly cutting edge material, but then when scanning 4x5 inch sheet film maybe they don't really need to be. In terms of resolution, they do not cut the mustard (so to speak) when scanning 35mm with the intention of printing bigger than 5x7 inch prints, where a Nikon LS-40ED or LS-V ED is better, but its easy to get 1200 dpi out of them and some bureaus only provide 2400dpi for A0 sized prints anyway.

Anyway, back to the Epson. I've been interested to know just how well it really performs, so I bought a Stouffer stepwedge and scanned it to see how the scanner would perform. This is the result of a 'linear' scan with no curves applied.

Stouffer publish the data on this step wedge as:
number of steps density change density change in stops Dmax
21 0.15 1/2 3.05

The Epson scanners have a 'calibration' area at the top of the plastic film holder. This is used internally in the scanner to (I assume) to reference check the light source. I reasoned that if I covered that with something that blocked some of that light then I might be able to get better black out of it.

So, I got a bit of green OHP transparency sheet and used that to cover the scanner in a series of scans. I scanned the step wedge in the following manner:
  1. 16bit RGB scan
  2. 16bit greyscale
  3. 16bit greyscale (one sheet of green OHP transparency)
  4. 16bit greyscale (two sheets of green OHP transparency)
My results are interesting.

tablet step RGB no cover (Green channel) greyscale plain greyscale 1 sheet greyscale 2 cover
1 230 233 254 253
2 192 192 226 237
3 153 155 183 210
4 126 127 150 175
5 101 104 123 142
6 85 85 102 120
7 69 71 83 96
8 56 57 67 79
9 45 47 56 65
10 38 40 46 54
11 32 33 38 45
12 26 28 33 38
13 24 24 28 32
14 19 20 24 28
15 16 17 20 24
16 15 15 18 21
17 13 13 16 19
18 11 12 15 18
19 10 11 14 16
20 10 11 13 15
21 9 10 12 15

Here is the graphic view:

You can see that a log(10) plot (scale on the LHS is more or less linear until about step 17). The straight sample data is plotted on the RHS of the graph.

My interpretation of this is that:

1) the scanner runs out of grunt at about step 16 or 17 and only pulls the last dregs out of shadows. I don't mind this for my negatives (which are seldom so dense), but I think it makes it clear that this is not the beastie for scanning slides (especially slightly dense ones).

2) covering the calibration area yields better white point selection, with the best results (not published here) coming from using a piece of unexposed but developed film as the cover (say a section of film leader, or sacrifice a sheet of film). This has the advantage of maximizing the separation of the data and bringing up the dark end of the scale by a stop or so.

I will be keen to test my 4870 next

Thursday, 20 March 2008

Faith restored

For the last few months I've been looking at some of my large format camera images and shaking my head ... is it my wide angle lens (Fujinon 90mm f8) ... I don't know. My images just weren't sharp enough for my tastes (not to mention the time and energy put into capture).

The clue came when I was testing some new (to me) film, and I happened to use my 90mm and my 10D for metering. I was doing metering and film speed testing and my first impression of the test was that my metering system was working well, but I quickly spotted that the digital was so much sharper than my 4x5 negative.


Looking about the image I soon discovered that vibration was at work, as I spotted that the LED on the small stereo was not a precise dot, but more oval looking! (note the section highlighted and zoomed in on the left here)

Using judicious quantities of BluTac to 'nail' my camera down onto a table, I have decided that my new Manfrotto 190 tripod just isn't up to the same levels of stability as my old one was.

It holds the camera, but a laser pointer placed on the camera shows that the thing vibrates like a tuning fork when faintly touched, or (worse) when the shutter goes click. A quick look at the 'stem' of the tripod shows that the head is now attached to the neck by plastic!

The cheapest solution for me was to attach drinking straws with some BluTac to the camera and the tripod legs to 'brace it up'. Looks odd, but it works. So now I'm getting the details I'm hoping for in my pictures. For example this shot of the forest floor the other day.

Shows the right amount of detail, and this is only a 1000dpi scan of the film!

whereas my 5Megapixel digital shows only this amount of detail (below) and even taken with more 'zoom in' than the film image.

Just what I expected to see.

So now I'm comfortable with my imaging systems again, and know that new Manfrotto tripods are not what they used to be.

Thursday, 6 March 2008

I'm no economist but ...

I was reading the paper this morning, and saw this:

"Meanwhile, ABS trade data showed the value of imports soared by five per cent or $1 billion in January. Rising imports helped push out the goods and services trade balance to a bigger than expected deficit of $2.723 billion, a blow-out of almost $800 million from December. It's the second worst trade gap on record."

It reminds me of a short piece by C. J. Dennis called The Glugs of Gosh. In this story, foreigners who were once the enemy of the Glugs approached the King and Queen with a neat importing deal...

"We'll sell you pianers and pickels and spanners
For seventeen shiploads of stones:
Smooth 'uns or nobbly 'uns,
Firm 'uns or wobbly 'uns,
All we ask is stones."

It all sounded very good, but eventually someone noticed something wrong.

But a Glug stood up with a cast in his eye,
And he said, "Far too many baubles we buy;
With all the Gosh factories closing their doors,
And importers' warehouses lining our shores."

Despite reports on how much more we're spending plenty on shipping out more and more rocks (coal can be thought of as a rock) are we just fooling ourselves that our economy is getting better.

It seems to me like we're going from having a low paying job at the supermarket to getting a slightly better one, then using your newly approved credit rating to go buying new clothes, stuff around the house and a car.

So while we are shipping out more rocks all we seem to be doing is to get into deeper debt and stripping ourselves of any manufacturing and skills base.

Monday, 3 March 2008

Nanny knows best

A friend of mine from England once pointed out to me that Australia is not really welfare state, we're more a "Nanny state", with our Nanny taking control over what ever it can, and administering us like ignorant children. It would be more reassuring if our Government departments were perhaps apparently wiser and more consistent in the way it administers things. Even previous Governors in our colonial past have struggled with the administration of Australia. So as Easter approaches, all sorts of European goodies appear in the shops which are not found at home, I'm reminded of a situation from a few years ago, which sort of illustrates my point.

Here in "Sunny Suomi" (Suomi being the Finnish name for Finland) is an excellent chocolate company called Fazer (they Finns say it more like "Fatser"). Among their delicious selection is a lovely almond and hazelnut nougat egg called the Mignon egg.

These are sold only at Easter, so they are a special treat.

The nougat is rather like a more solid version of a well known spread at home called "Nutella".

Not only do they taste beautiful, but Fazer take the presentation to another level by pouring this delicious chocolate into a real egg shell, just like the traditional boile eggs we had as kids for easter only better as they're chocolate!

Because the chocolate is encased in a natural egg shell, you can then get the kids to decorate them with water colours, just the same way that you did when you were a kid yourself.

I thought they were so lovely I just had to send some to my family and friends in Australia.

But wait, at Easter instead of my family getting these eggs, they got a "seizure notice" from Customs ... apparently Nany says "no"! You see, Nanny says that these cute looking food items are in fact terrible vectors for the transmission of feared disease of bird flu to the fair and beautiful shores of Australia. Hard to see how the virus could have survived the cleaning process, but Nanny knows best.

As you'll see, because Nanny knows best she's carefully prepared a document about this, to lay clear to the regulations on importing food items here. This clearly outlines what you can and can't do with the import of items which are designated as "End use: Human consumption".

However the officer who works for Nanny seems to have thought that these chocolate eggs were not actually for human consumption, but were in fact to be designated "End use: All uses other than as animal foods, fertilisers or for growing purposes" (what a shame to waste the chocolate nougat). This meant that the food items must of course abide by different rules, they being those in this document here which covers decorations and non food items.

These rules I am told forbid the import of these cute Easter eggs. Before you go further, just scroll back up and look at that egg again, now lets have a look at the rules with the actual product in mind.

My gift came under the Non-Commercial rules, and I'll point out here that I've highlighted some parts in bold, and put my personal comments in italics within brackets [notes].
  1. An Import Permit is not required.[note how this assumes that my friends and family are in fact importing a gift sent to them by me without their knowledge]
  2. A Quarantine Entry is required for all consignments except those that are imported as non-commercial consignments by mail or those that are imported as personal consignments with passenger's accompanied baggage.[note: luckily its not required, but again my (and your) family are already supposed to importers of your surprise gifts]
  3. Professionally prepared undecorated and decorated blown eggs or egg shell ornaments/paintings may be imported without treatment, if a manufacturer’s declaration or similar documentary evidence states these products have been mechanically and chemically cleaned of all organic material. Egg shell ornaments may be painted or lacquered.[Note 1: while it is true that the shell of these easter eggs is a blown eggs, it is not actually a decoration and it remains silly to consider these items as other than "intended for consumption". Note 2: my chocolate easter eggs were supported with a document provided by Fazer chocolate company. But that did not satisfy Nanny, she's not easilly fooled by inferior EU food quality standards]
  4. All egg ornaments and paintings are subject to inspection on arrival. Blown eggs that appear not to have been professionally prepared, or where any cleaning process is unknown, cannot be imported unless treated bywashing the outside and inside of the shell with 2% sodium hypochlorite for a minimum of 10 minutes (T9372), 1% Virkon or 1% Virucidal X (T9431) or gamma irradiation at 50 kGray (T9652) [note 1: these are not egg ornaments, but food items. Note 2: the officer suggested that if my easter eggs were treated this way he was prepared to release them, but then of course, they would no longer be fit for human consumption as intended ... but wait ... why are we applying this regulation to Food items? Nanny knows best ...]

Despite assurances from the Fazer company with written certification that that these egg shells have been washed and sanitized fit for human consumption (Note we're dealing with a chocolate company and a food item? So why are we still arguing this interpretation of regulations? Nanny knows best...)

Nanny knows best, she rigorously stands guard protecting my beloved family and environment from nasty exotic diseases, you won't get anything past her (unless you're a major shipping line pumping your bilge into the harbor introducing God knows what, or a commercial importer bringing in containers of furniture containing South East Asia Asian Geckos, or a pet shop bringing in exotic pet fish that your clients are able discharge into river systems... the list goes on).

While I admire and respect my Nanny for this laudable goal, perhaps someone should point out to Nanny that there are several million migratory birds (such as the Arctic Tern) which move between Asia (the central location for the dissemination of this disease btw) every year, and don't bother to declare themselves at Customs. Perhaps they may serve as better vectors for the introduction of this disease than some chocolate eggs from Finland.

I find it extraordinarily frustrating to observe the application of rules by a bureaucracy which is making strange decisions about these tiny details, while we still bring in exotic fish, continue to plant exotic species of plants beside world heritage national parks (resulting in their infiltration into the area) and numerous other apparent double standards.

Anyway, probably the staff at Customs enjoyed 'safely disposing' of these tasty chocolate eggs (even if my friends didn't get the chance). Well, perhaps I'll send some fly swatters to help my family with the insects this summer instead.