Thursday, April 29, 2010

Behaviors of SLR Lenses on Canon APS-C

Field of View
Comparison of the field of view you get at various focal lengths and lenses. It's easier to visualize with pictures. The camera is a Canon Rebel T2i (aka 550D) which has an APS-C sensor (1.6 crop factor). Camera is tripod mounted while lenses are changed. Sorry, I forgot to take "normal" range photos with the zoom. I'll do a second set of tests for that. These still images are at 4:3 Aspect Ratio. Video mode will crop the top and bottom to form a 16:9 image.

11mm (17.6mm effective)
Tokina 11-16 AT-X Pro 2.8 (Zoom)
16mm (25.6mm effective)
Tokina 11-16 AT-X Pro 2.8 (Zoom)
18mm (28.8mm effective)
Sigma 18-50 EX DC Macro 2.8 (Zoom)
50mm (80mm effective)
Sigma 18-50 EX DC Macro 2.8 (Zoom) 
50mm (80mm effective)
Nikkor SC 50mm 1.4 (Prime), adapted from F-mount to EF
Note how the view is narrower than the Sigma above.  Infinity focus is slightly before the infinity marker on the lens.
70mm (112mm effective)
Canon EF 70-200 F2.8/L IS (Zoom)
85mm (136mm effective)
Canon EF 85mm 1.8 (Prime)
200mm (320mm effective)
Canon EF 70-200 F2.8/L IS (Zoom)








Focus Breathing
A slight change of FOV may be observed when changing focus.  All the SLR lenses from the previous test exhibit this to some degree.

Focused to Foreground
Note the trees on either side of the picture.  Focus to foreground which is about 9 feet away shows less of trees on either side.  Lens is a Canon EF 70-200 F2.8/L IS at 70mm.

Focused to Background
Focus to background shows more of the trees on either side.  Lens is a Canon EF 70-200 F2.8/L IS at 70mm.







Lenses Tested
Tokina 11-16MM F/2.8 ATX 116 Lens for Canon EOS AF Digital - Tokina ATX116PRODXC
Sigma 18-50mm f/2.8 EX DC SLD ELD Aspherical Macro Lens for Canon Digital SLR Cameras 
Canon EF 85mm f/1.8 USM Medium Telephoto Lens for Canon SLR Cameras 
Canon EF 70-200mm f/2.8L IS USM Telephoto Zoom Lens for Canon SLR Cameras 


Canon 7D vs T2i Video Mode Controls

The controls behave differently between stills and video mode. This is for video mode.

Switch to Video Mode
T2i
Turn mode dial to movie icon. Message appears if adapted lens is attached. Mirror locks up, LCD or external monitor turns on. Push Live View button on camera's back to record. Red circle appears in upper right when recording.

7D
Push throw switch left to movie icon on camera's back. Message appears if adapted lens is attached. Mirror locks up, LCD or external monitor turns on. Press Start/Stop button to record. Red circle appears in upper right when recording.


Changing Video Shutter Speed
T2i
Turn wheel near shutter button right to increase shutter speed. Recommended shutter speed is 50 (1/50) for 24fps, 60 (1/60) for 30fps, and 120 (1/120) for 60fps. This is to conform to 180-degree shutter rule.

7D
Turn wheel near shutter button right to increase shutter speed. Recommended shutter speed is 50 (1/50) for 24fps, 60 (1/60) for 30fps, and 120 (1/120) for 60fps. This is to conform to 180-degree shutter rule.

Changing Aperture of EF Lenses
T2i
Hold down AV button near LCD. Turn wheel near shutter button right to increase F-stop (darker). Turn left to decrease F-stop (brighter).

7D
Turn body dial right to increase F-stop. Turn body dial clockwise to increase F-stop (darker). Turn counter-clockwise to decrease F-stop (brighter)

Changing ISO (boost brightness)
T2i
Press ISO button once near shutter button. Turn wheel near shutter right to move from Auto ISO, 100, 200 ... 6400 (default, extended ISO turned off). LCD displays ISO value in lower right corner. Selection wraps around.

100-400 ISO typical for daylight. 1600 indoors starts to show image noise. Default Max setting is 3200 for Auto ISO.

7D
Press ISO button once near shutter button. M-Fn wheel near shutter right to move from Auto ISO, 100, 125, 160, 200, 250 ... 6400 (default, extended ISO turned off). LCD displays ISO values. Selection wraps around.

100-400 ISO typical for daylight. 1600 indoors starts to show image noise. Max gain in Auto ISO feature is not available on 7D. Maximum Auto ISO is 6400 when high mode is not enabled.

Saturday, April 10, 2010

GoPro HD Hero nuts

The HD Helmet Hero doesn't have a nut to go with every mount. My Google searches misled me at first. 10-32 is NOT the correct size. It's Metric 5mm. At Home Depot you can find it in the red trays marked Hex Nut 4-12mm size. You want the one marked HEX NUT 5mm-8 which contains 2 pieces. It was $0.41 + tax at the time of this post.