Wednesday, 29 October 2014

Electronic shutter readout speed

Many modern system cameras feature the electronic shutter option. This means that you can take pictures silently, without activating a mechanical curtain shutter. Rather, the exposure is started and stopped electronically.

The Nikon 1 series is pretty much built around electronic shutters. The basic J and S series of cameras do not even contain any mechanical shutter at all, you only have the electronic shutter option.

The downside of the electronic shutter is that not all the sensor is read at once. Rather, the sensor photosites exposures are started and stopped row for row, vertically. This process of starting and stopping the exposure, and then collecting the exposure data, can take around 1/10s to 1/100s, depending on the camera model.

The slower, the less useful the electronic shutter is, as you can risk rolling shutter effects, buildings appear to lean if you pan while photographing, for example.

Rolling shutter effects are not exclusive to digital cameras. Rather, they were present also with early film cameras. Here is a famous photo of a racing car taken in 1913 by Jacques Henri Lartigue using a 4x5 Speed Graphic camera:

The curtain shutter moves relatively slowly on this camera 100 years old camera, when compared with modern SLRs, which gives the distortion of the racing car. The distortion is especially visible in the wheels, which appear to be leaning forward. This rolling shutter effect was later copied by cartoonists when they wanted to give the impression of speed.

Saturday, 18 October 2014

High speed video, slow motion

Already from the start, Nikon 1 cameras have been able to record video at a 1200 frames per second rate, which is very fast. A normal video frame rate is 30 FPS, in NTSC countries, so you are able to record videos 40 times as fast.

This can be used to make interesting slow motion videos. In this example, I used a Nikon 1 J1 to record the mechanical shutter of the Lumix GM1 camera.

The newest Nikon 1 V3 camera also has the high speed video feature. It can record 1200 FPS, without audio, and in an unusual 416x144 pixel resolution. When the video recording is started, it lasts only for 3 seconds, so the timing of the start of the video is crucial.

Saturday, 11 October 2014

Comparison of normal lenses, Nikon 18.5mm f/1.8 vs Leica 25mm f/1.4

Some decades ago, when film SLR cameras became popular, the 50mm lens was abundant. Due to the long register distance of SLR cameras, the 50mm lens was the shortest which could be designed cheaply with a large aperture, which is why it became so popular. It became the standard lens people bought with an SLR camera, the normal lens.

Nowadays, the kit zoom lens has become the normal lens, but the field of view corresponding to a traditional 50mm lens is still popular. So most manufacturers release a fast "normal lens" when they invest into a new lens mount. In this article, I will compare two normal lenses for two different systems, the Nikon 18.5mm f/1.8 for Nikon 1, and the Leica 25mm f/1.4 for Micro Four Thirds:

LensNikon 18.5mm f/1.8Leica 25mm f/1.4
AnnouncedSep 13th, 2012Jun 13th, 2011
System crop factor2.72
Equivalent focal length50mm50mm
Maximum aperturef/1.8f/1.4
Equivalent max aperture, in terms of DoFf/4.8f/2.8
Filter thread40.5mm46mm
Minimum focus0.20m0.30m
Lens elements/groups8/69/7
Hood includedNo, HB-N104Yes
Focus ringNoYes

Both correspond to 50mm field of view on a 135 film camera, and both are quite fast, with large maximum apertures: