alignment photos on Flickr

Perfect Alignment by Nick Hovey

As the locomotive is lowered, careful watch is given to the alignment of the wheel flanges with the 2"x2" steel bar rails welded to the deck of the flat car.

Workforce Alignment Workshop by University of Wisconsin Oshkosh

Workforce Alignment workshop "Building strong partnerships to support Wisconsin’s workforce need." A conversation hosted by UW Oshkosh, Department of Workforce Development, Fox Valley Tech and WAICU.

Planet Alignment by Ed Dunens

Finally a break in the clouds! Lake Wendouree. Ballarat.

New York State Route 12 - Old Alignments by Doug Kerr

New York State Route 12 - Old Alignments in Greene

Perfect alignment by David Francis

John Bevere at CFNI by CFNI

Take a look at John Bevere speaking at the opening night of the 2016 Alignment Conference.

FD55FR_Alignment by tony_duell

Aligning the head on the floppy disk drive using an old Amstrad laptop and a test unit called a 'Microtest' This uses the normal analogue alignment disk. Note the special alignment tool screwed into the stepper motor bracket at the rear of the disk drive (left side in the photo)

Alignment by Bill MacEwen

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alignment and subtraction. by Ant00n

I'm trying to find out the following:

* does optical distortion of a lens at a given focal length change with aperture.

I did this by taken 2 pictures at 2 different apertures and identical focal length.

I overlayed them in gimp and set the layer type to subtractive. so what you see is pixel A - pixel B. i.e. the greater the difference, the more luminance and color. Less difference the more black.

However, I forgot that it would be a good idea to pick a focal length that actually shows some visible distortion so the effects can be more easily seen.

As it stands, this lens is pretty ok at 31 mm.

I do notice that it is not possible to align the images entirely. In the image, you can see that I aligned both layers so that around the 92cm mark, the millimetre marks are most black and with the least halo like edges.

The green edges which you can notice at the decimeter marks (the boxes) are on the right side in the left side of the image, and vice versa on the left side of the decimeter mark on the right side of the image. This to me seems to indicate some sort of a scaling issue, i.e. likely caused by zoom lens creep.

I've prepared another alignment this time properly done on the left side. the difference is about 6 pixels. Relatively speaking: +/- 0.05% as measured from the center.

What Does show though is that there is no barrel/pincushion distortion difference between the f/4 image and the f/22 image. Sadly, looking up the measured distortion for this lens, dxomark.com reports 0% distortion around the 30mm focal length:

www.dxomark.com/index.php/Lenses/Camera-Lens-Database/Can...

So even if there was an amplification effect of aperture on distortion, this experiment fails to show it due to hitting the perfect distortion free focal length for this length.

Another round at 24mm is needed I'm afraid, since the lens doesn't fare so well with regards to distortion.

Shinchonji_National_Sports_Competition_4th_6 by Hello Shincheonji