UPDATE: At the end of July 2008 Canon released firmware update (version 188.8.131.52), which resolves the problem described below. The update is available at http://web.canon.jp/imaging/dcp/firm-e/hv30/.
HV30 is Canon’s latest consumer-grade HDV camera, praised for it’s remarkable HD quality in it’s class. But when it comes to Standard Definition (SD), things are different. There’s a serious flaw which appears in SD mode and makes shooting SD footage with HV30 questionable.
The flaw only appears when shooting in SD mode (both wide and standard) and having shutter speed less than 1/25 of a second. If these conditions are met the video quality worsens dramatically. Everything is fine with shutter speeds greater than or equal to 1/25 and no other setting but shutter speed seem to reveal this problem.
See the images below. These are unaltered frame crops from two separate video clips made with the same camera on tripod with same settings. Only the shutter speed differs.
On the left is a crop from frame (SD wide format) shot with shutter speed of 1/25 and on the right is the same scene shot with shutter speed of 1/50. You can click on the images to see full-sized frames.
As you can see on the right image (Figure 2), the vertical resolution drops dramatically with shutter speed of 1/50. You can notice it as stair stepping. Horizontal resolution does not seem to be affected.
To be precise, with shutter speeds less than 1/25 the vertical resolution is only half of what it should be! Here’s a frame crop to demonstrate it. The first video clip shot with 1/25 (Figure 1) was opened in VirtualDub (using MPEG2 input plugin) and “Duplicate field 1″ deinterlacing filter was applied to it. You can see the result on the right. This filter removes every even line from video frame and replaces them with duplicated odd lines, thus reducing the actual resolution by half. If you compare VirtualDub’s output on the right to Figure 2, you don’t notice much difference. You can see that camera acts the same way as filter does – it discards half of the vertical information. But it should not.
When you look at the specification section in HV30 instruction manual, you can see: “Television System: SD – CCIR standard (625 lines, 50 fields) PAL color signal”.
Well, it is only partly true. With shutter speeds < 1/25 the vertical resolution does not comply to CCIR 601 (ITU-R BT.601) standard (and Canon’s specification).
So far there are no known resolutions to this problem. Theoretically It should be fixable by firmware update, but there’s no firmware updates available for HV30 at the current time.
Camera used for this test was an European (PAL) version of HV30 with firmware 184.108.40.206.
There are similar reports from other HV30 PAL users. NTSC version doesn’t seem to have this problem.