Achieving Depth of Field with the Canon XH A1
This past year as seen the phenomenal growth of the Digital SLR (DSLR) market for cameras that now also shoot HD video – either 1280 x 720 or 1920 x 1080, depending on the camera. This market is about to take a huge leap forward over the next few months as all the camera makers introduce new products that begin to support video needs much better than their first or second generation cameras.
DSLRs are becoming popular for video photography because:
- Many still photographers have quite a collection of lenses that are a much larger investment than the camera body! Now they can put those to use for video too.
- Having the combined function of both high quality still and video in one camera is very convenient. In a national park in Canada recently, I was carrying a non-video DSLR, an extra lens, extra battery, a Canon HV30 video camera, a wide angle lens, extra tapes and extra batteries – plus a video tripod – on an 8.5 mile challenging hike. That hike convinced me that next year, I’d like to have a video capable DSLR! Less stuff to carry!
- DSLRs are capable of narrow depth of field in a way that most video cameras cannot do – except for extremely expensive professional cameras.
- DSLRs can use special effect lenses to create unusual optical effects, such as making the real world look like miniature models! (My wife thinks that is funny since so many in the movie making world work very hard to make their models look like the real world – now we try to make the real look like a model!) For example, see this.
- DSLRs can be used less obtrusively to shoot video than using larger cameras like the XH A1 or Sony EX-3.
To video photographers, DSLRs have their drawbacks – so far. Typically their audio feature set is limited. They display video only on exterior LCD panels, which may not be tiltable (this is changing for the new models) and which is hard to see in daylight. They limit maximum clip length to 12 minutes or similar. They often do not auto focus in video mode and there is no such thing as a motor driven slow zoom – they are all manually operated.
But the one feature that stands out in videos shot on DSLRs is their depth of field capabilities. They can achieve narrow depth of field because their image sensors are much larger than typical video cameras. The larger the sensor size relative to the lens, the easier it is to have that narrow focus range.
The good news is that you can kinda sorta achieve some DoF capabilities with the XH A1. At the wide angle setting the lens opens up to f1.8. It stops down a bit on telephoto. If you manually control the aperture (set to the Av setting) you can achieve some nice DoF effects. Its not the same as a DSLR, but there are some decent views that you can obtain this way. I’ve done some experiments to get some effects I wanted – and its okay.
A possible problem is when you open up to f1.8 in bright sunlight, the shutter speed may drop to 1/600 or worse. For moving subjects or pans, this may create too much of a strobe effect at 24f or 30f frames per second.
An alternative is to use neutral density filters. I have not yet tried this – but with external ND filters (in addition to those built in to the camera) it should be possible to shoot at wide apertures with a lower shutter speed like 1/30th to 1/100th of a second.
Anyone try this yet?