Archive Page 2

29
Jul
09

Maybe LightRoom wasn't that slow

A while back I wrote about how slow LR was when using gradients and brush tools. Even on my 8-core MacPro, the beach ball kept on spinning forever. Today, as I was watching the L-L video “Where are my #$$$”% images”, I realized that I had turned on the “Automatically write changes into XMP” option. This makes LR write every single movement on my sliders into the XMP sidecar file (or the DNG file) as I do the movement, and the slowdown is caused by the disk bandwidth. When I turned off this option, LR in snappy, and I am happy.

So, go into the catalog settings and uncheck the “Automatically write changes into XMP” option inside the “Metadata” tab. You should also go into the “View Options” under the “View” menu, and tick off the “Unsaved Metadata” checkbox. That way you will get a small arrow on each photo that contains unsaved metadata. Every once in a while, and at least every time you quit the session, select those photos and hit Cmd-S. You will not lose work even if you don’t save, but then the metadata is only stored in the LR database file, and not as part of the image file. If the metadata is stored in the image files, you will get back everything if you reimport them into a new catalog, which is good if the lightroom catalog gets corrupted.

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22
Jul
09

Auto focus is confusing?

I while back, I looked through the archives at Cambrigde In Colour, and found this article about auto focus technologies. The author tried to describe how the autofocus of dSLR’s are working, when in fact he was describing the contrast based autofocus most commonly used in compact cameras. Later I found Tim Jacksons D70 site, where he also describes a focus system that I don’t really think exists in any camera on the market. After looking around on the net, it occurred to me that there are many attempts to explain autofocus out there that are just plain wrong. It seems like the phase dection autofocus system used by all SLR cameras, both digital and film, is a bit hard to grasp, so most authors explains the conseptually more easy contrast based autofocus instead. Or maybe they just fail to see that there is a difference.

Contrast based auto focus

To start with contrast based auto focus. This type of system is most commonly used in compact cameras, and on some dSLR’s when the Live View function is used. It uses the actual imaging sensor to determine focus, and here is how it works:

  1. It shoots a series of images at different focus settings.
  2. For each of these images, it will determine how  much contrast there is in the designated focus areas.
  3. It selects the image with the most contrast, and reset the focus to the value it used to capture this image.

This process is relatively slow since the camera must take a large number of shots and process them before finding the focus. On many cameras you can observe this if you look at the lens while trying to focus. It will cycle focus from one endpoint to the other before it snaps back to somewhere in between which hopefully is the right focus setting.

A major drawback with this kind of focus is that the camera has no way of predicting if the focus is in front of, or back of the current setting. It must just try in one direction and hope that it is right, and if not, it must go the other way.

Phase detection auto focus

This type of auto focus works kind of like the good old split prism in the days of manual focus. The focus system will take a part of the light coming from one side of lens and project it on one sensor, and a part of the light coming from the opposite side of the lens and project it on another sensor. These sensors are dedicated AF sensors, and are usually formed as narrow strips. When the image is in focus, the two images are perfectly aligned, but they will get more and more misaligned as the system gets more and more out of focus. Just like the split prism, all the AF system has to do is to rotate the focus until the two images are aligned.

A major benefit with this type of AF is that it can predict which way the focus shall be turned. Not only that, but it can even predict how far it shall be turned. This is accomplished by detecting to which side the misalignment is, and how much the images are off.

Here is a short drill down how it works:

  1. The AF sensor detects the direction and amount of misalignment.
  2. Based on the information about the lens, if predicts how far the focus must be turned.
  3. The focus is then adjusted accordingly (focus is not measured when this happens since the focus changes too fast).
  4. When the focus motor stops, a new measurement is performed. If the focus is not perfect the drill (1 through 3) is performed over again, but now the adjustments are much smaller, and therefor more precise.
  5. This goes on until the focus is good, or the system times out because it is unable to find focus.

The big misconception is that this system optimizes contrast, when in fact it correlates two one-dimensional images. When the contrast based system relies on a sharp edge to focus, this system only need some sort of recognizable pattern. In theory, it should be able to focus on a smooth gradient that goes along the focus sensor.

Here is an illustration by Canon (go to the bottom of the page).

And here is the Wikipedia article.

So, this is an overview of my understanding of these systems. If anyone more knowledgeable than me finds this to be wrong, please write me a comment.

22
Jun
09

a nice text editor

I just came across a really neat little application. It’s called jDarkRoom, but even though the name suggest some sort of relation to photography, it’s not. It’s a very simple text editor with a rather unique feature.
When you start jDarkRoom for the first time, it will fill the entire screen with black, removing all menus, task bars, docks and everything. When you start to write, green text will apear using a simple monospace font. The idea is to minimize the number of distractions while you write. It is also the most basic text editor you’ll ever find, featuring only the basic funcitons like open/save, cut and paste, and search functions. Some may consider this a drawback, but for me it is all I ever want.
When I write a piece of text, instead of using a word processor (like Word or OOWriter), I prefer a simple text editor for its pure simplicity. I will usually start to capture the content, adding formatting, graphics and tables later. A word processor distracts me, and I start to worry about formatting and figures as I write, breaking the flow. When I have written things more or less finished, I will paste it into a real word processor for spell checking, layout and formatting. Another good reason why I don’t like writing in word processors are the tendency they have to pause everything for some background task. Not too seldom, I find I have written more than a sentence before the word processor wakes up and start the catching up. The basic text editor is snappy.
This editor is not suitable for coding, but it will probably be my first choice for capturing ordinary text.
You’ll find it here (http://www.codealchemists.com/jdarkroom/), it is written in Java and is available for all platforms. I’ve tried it on both Mac and WinXP, and works fine.
PS.
I may slow down on posting here, not shutting it down completely

I just came across a really neat little application. It’s called jDarkRoom, but even if the name suggest some sort of relation to photography, there is none. It’s a very simple text editor with a rather unique feature.

When you start jDarkRoom for the first time, it will fill the entire screen with black, removing all menus, task bars, docks and everything. When you start to write, green text will apear using a simple monospace font. The idea is to minimize the number of distractions while you write. It is also the most basic text editor you’ll ever find, featuring only the basic functions like open/save, cut and paste, and search functions. Some may consider this a drawback, but for me it is all I ever want.

When I write a piece of text, instead of using a word processor (like Word or OOWriter), I prefer a text editor for its pure simplicity. I will usually start to capture the content, adding formatting, graphics and tables later. A word processor distracts me, and I start to worry about formatting and figures as I write, which breaks the flow. When I’m more or less finished writing, I will paste it into a real word processor for spell checking, layout and formatting.

Another good reason why I don’t like writing in word processors are the tendency they have to pause everything for some background task. Not too seldom, I find that I have written more than a sentence before the word processor wakes up and start the catching up. The basic text editor is snappy.

This editor is not suitable for coding, but it will probably be my first choice for capturing ordinary text.

You’ll find it here (http://www.codealchemists.com/jdarkroom/), it is written in Java, available for all platforms, and it’s free. I’ve tried it on both Mac and WinXP, and works fine.

PS.

I may slow down on posting here, but I don’t intend to shut it down completely.

19
Jun
09

Transition to Norwegian

Sorry about the slow posting, but I’ve finally started my long planned transition to more writing in Norwegian. I have just got a Norwegian blog up and running with a couple of posts, and I guess it’ll be more geeky stuff there along with the photography related. I guess I can’t deny it any longer, I’m a computer and gadget geek as much as I am an “serious amateur photographer”. So the English blogging will probably scale back to more picture publishing and some occasional comments, at least for now.

Also, I won’t deny that having a 2 month old son is putting some restrictions on the web activities, but not as much as I would have expected. He’s really very nice, sleeps well at night.

Anyway, if you read Norwegian you can stop by http://speilbildet.no

If not, just keep me in your RSS reader, who knows when I find the time to post something.

11
Jun
09

WordPress 2.8

Just upgraded to WordPress 2.8, and it works fine (as far as I can tell)

06
Jun
09

Ambigrams is getting some attention

About 2 year back I posted a couple of Ambigrams I made of my own and my, then fiancee, now wifes name. You’ll find them here.

Now they get som google attention again with the release of “Angels and Demons”. Ambigrams are a central part of the plot in that book, and in the film also I presume. The book sucked so hard you won’t believe it, so it shouldn’t be too hard to make the movie better. I acutally enjoyed reading “The daVinci Code”, but “Angels and Demons” was just crap.

Anyway, funny how a movie affects what people googles, and that the stats pick up these things.

06
Jun
09

Back on the streets again

Today I had a good hour on the streets with my 5D and a 50mm lens. It’s been a long time since I used the 50mm now, but it was very pleasant to carry a setup that didn’t scream “PHOTOGRAPHER” two blocks away.

While my Canon zooms, namely the 70-200 f/4L IS, the 24-105 f/4L IS and the 17-40 f/4L are magnificent, they are also huge. That’s a big problem on the street, but even while doing nature photography it’s a problem. Due to some back problems, I am reluctant to carry more than one of those lenses, and even then the setup is heavy on my sholder. Im really thinking more and more of the Pentax gear. So far the starting setup would look something like this.

  • K7 body
  • The kit zoom for family snaps (doesn’t really add much cost)
  • DA 21mm f/3.2
  • DA 35mm f/28 Macro
  • DA 70mm f/2.4

After that, some potential candidates would be

  • DA 15mm f/4
  • DA* 50-135mm f/4
  • DA* 16-50mm f/4
  • DA* 55mm f/1.4

It is always good to have a zoom or two, and the DA* lenses are weather sealed as well, so there is an added benefit.

Anyway, here is some of the pictures from today. Remember, click on them to see a bigger version.




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