Different shades of red
November 28, 2007 § 6 Comments
When filming surgery, some special issues must be considered. One of those are the color red.
Because of the blood running through our body, most of our organs and tissue is some shade of red. To distinguish the different anatomical structures from each other it is crucial that the video system used is able to reproduce the colors accurately.
DV and HDV
DV, and recently also HDV, are very popular formats both in the medical world and in the video production community. Both DV and HDV are heavily compressed formats. They run at approx. 25 Mbit/s. Some of the reduced data rate is obtained by lowering the chroma sample rate. For both DV (PAL) and HDV the sampling format is 4:2:0 (more on chroma subsambling here). The recorded color signal is under a quarter less accurate than the luminance signal. This is simply not enough to reproduce the different shades of red satisfactory.
This is the main reason why I shoot on DVCPro50 when I can. Not only is this format less compressed (50 Mbit/s), it also uses a sampling format of 4:2:2. The recorded chroma signal is 50 % as accurate as the luma signal. This results in little to no visual difference from 4:4:4 sampling, as our eyes are more sensitive to luminance than to color.
Using DVCPro50 largely increases the ability to reproduce the colors of our insides accurately. When shooting minor surgery and biopsies I use the Panasonic AG-HVX200 in DVCPro50 mode with the Firestore FS-100 hard disc recorder and the DVRig Pro camera support.
For shooting major surgery I have just built a custom made camera support. Footage from this system is currently recorded on DV.
More about the handheld rig and my new surgery video system later.
[…] while back I wrote this post about the problems video cameras have with reproducing the insides of our bodies. The blood running […]
Hi Sterile Eye,
Very interested to read your stuff. I’m a Hong Kong based video journalist and producer, and am being called upon more and more to shoot surgical procedures by the medicos at Hong Kong University where I do some part-time lecturing. Interesting to read your comments on the ‘red’ limitations of DV and HDV. (I shoot on a Z1 and A1.) Would be keen to know what kind of support you use for your camera ?
Great that you found something of interest here.
I’ve mostly been using the DV Rig Pro. It’s great for keeping the camera above eye level and out from your body, which is very useful when shooting over the anesthetist screen.
I also use a custom made stand which allows me to place a remote controlled camera straight above the surgical field. I’ll post on that sometime soon.
Impressive CV, by the way!
[…] November 2007: Different shades of red About the problems involved in rendering our inside’s different shades of red on video. Read the post. […]
[…] extreme macro lens. As for surgery, I’m looking forward to see how the camera handles all the different shades of red and the extreme contrasts of the […]
Hi to all.
I use the new canon XF305 with 4:2:2 color sampling at 50 Mbps with almost good results.
A good rig I use is the manfrotto accessory arm 131DDB that will let you offset your camera about 60cm from the center of your tripod, and in so I can shoot from over the anesthetist screen without interfering with his work.
Pics on my website: http://www.live-surgeries.com
About the MarkII … there is no remote control for the zoom or the push AF available, and so, I can’t use it in my work.
Neither an HD SD output, so I can’t use it during a live transmission too!