View allAll Photos Tagged Alignment
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.
Fill it with goo, and then use the pump ... punctured tyre explanation ...
Ladies Motoring Evening with Annette Carey of The White Room, Chelmsford Carriage Company, and Drinks of France.
Airport Drive shifts onto a new alignment to connect with the airport connector road before the intersection with Charles City Road.
The services we offer includes tire rotation or replacement, maintain proper air pressure, test the vehicle on an alignment track. Plus, we properly check the suspension and steering component and we will also give our customers an annual alignment check-up.
Mobil Service Station on the former Southbound alignment of NR1 / Pacific Hwy. This section is now a service road.
Southern length of the alignment. View from the south.
stonerows.wordpress.com/gazetteer/region/dartmoor/hook-lake/
Neil from the Chelmsford Carriage Company can not help himself and adds a little weight to one of the tyre quality demos.
Ladies Motoring Evening with Annette Carey of The White Room, Chelmsford Carriage Company, and Drinks of France.
Pair of stones forming part of the stone alignment (Scale 1m).
stonerows.wordpress.com/gazetteer/region/dartmoor/butterb...