Posts Tagged ‘focus’

It Wasn’t My Eyes!

December 30, 2009

I found out why I could not focus properly on the moon last night. My Canon EOS-30D’s viewfinder was not adjusted properly.

It was obvious when I looked through the viewfinder at a passing helicopter the next day. I must have moved the adjustment wheel inadvertently. I’d forgotten it was there.

Here’s the page from the Canon EOS-30D User Guide:

Canon EOS-30D Dioptric Adjustment

Canon EOS-30D Dioptric Adjustment

Another thing I liked about my old Canon A-1 was that it had a little shutter to close the viewfinder window. It was good for tripod work. Canon have done away with it on their consumer cameras. I think the EOS-1D has one.

A Little Bit Out of Focus

December 29, 2009

Last night I made a second set of test shots of the Thai moon over Bangkok. This time I tried manually focusing on the moon with my Canon 75-300mm lens set at 300mm.

Although the pictures looked all right in the viewfinder and on the LCD display, when I got them into Lightroom they were unacceptably blurred.

Moon Out of Focus

Moon Out of Focus

My first attempts when I let the camera auto-focus were much better. I was surprised that it could focus, but it did and it did a better job than my 53-year-old eyeballs.

I remember my Canon A-1 film SLR camera had two optical devices in the viewfinder to help you focus. (This was the 1980s before auto-focus was available).

The first were micro-prizms. They disappeared when the picture was correctly focused. The second was a split prism. This worked better in low light. You adjusted focus until the top and bottom half of the picture was aligned. This article talks about them and this article explains the optical theory.

I don’t think there’s a technical reason cameras no longer have these aids. They are available on professional cameras like the Canon EOS-1 series. I suppose manufacturers believe that autofocus works 99% of the time so they are no longer necessary for amateurs.

Capture One Version 5

October 29, 2009

Phase One has an interesting interview with Phase One’s Vice President of Research and Development, Claus Mølgaard. It’s got more content than the usual product introduction interview. You can read it here.

I’m fascinated by the idea of the Focus Mask. It’s puts a mask (in Photoshop terms) over your picture where (I guess) the opacity is related to how much the picture is in focus.

Here’s a screen grab from the Phase One Web site which is the best I could find.


Focus Mask in Capture One 5

Focus Mask


I guess it works in a similar manner to the autofocus on the camera – a contrast detection algorithm. However, that is the limit of my knowledge.

When we examine a picture I think everyone would agree what parts of it are in focus. But I don’t know how you measure that at the pixel level.

I have not used Capture One. I wonder if they will release the Focus Mask technology as an addin for Photoshop or Lightroom. It’s a classic software company problem. They could reach a larger market and make more revenue in the short-term by enhancing the dominant tools in the business. But they would lose a competitive advantage for their software. It’s a hard call for a company.

It is also interesting to try and read between the lines as Claus discusses their handling of Raw files from different manufacturers. Phase One (the makers of Capture One) compete in some ways as they also make camera hardware and lenses. I bet they have some interesting stories to tell of their relationships with the major vendors. “Coopetition” is a complicated thing.