50i or 60i Interlace Slomo compared to 720 60p

Varicam Numbers to Tape DVCPROHD records 960 x 720 luminance pixels other DVCPRO codecs record 1280 x 720 but not Varicam, don't get confused by this

HDCAM numbers to Tape 1440x1080 luminance pixels.

Varicam Processing has 10 bit AD camera head capable of capturing 1056 tonal steps The AD converts analogue signal from ccd to digital

f900 Processing has 12 bit AD capable of 4096 steps. (HDW750 has 10 bit)

The Look Varicam were first to introduce very effective in camera gamma curves. Sony introduced them in the f900 in 2003. There are many more cinegamma curves available now for the f900 than Varicam

Varicam has three 1 million pixel ccds

f900 and 750 have three 2.1 million pixel ccds

Deinterlace This process takes the two fields that make up an interlace frame and retags them as frames. So 60i becomes 60p. Since one field is made up of odd numbered lines and the other field comprises the even number of lines from the ccd when they are viewed separately they have missing lines. There are many software techniques that create the missing information. The cost varies but is the kind of thing that can now be done on FCP. Care must be given to the post workflow, some favor deinterlacing SD downconverts doing the offline then only converting what is needed once the offline is signed off. Proper interpolation is best rather than line doubling. Mileage varies.

Varicam frame rate Varicam always records at 60fps. So when shooting 25 or 30p it duplicates frames to make up the 60 frames needed by the recorder. It needs a post process to extract speed ramps. Speed ramps must be done on separate tape.

HDCAM Frame rate. HDCAM recorder can run at varying frame rates, from 23.98 p to 60i. Speed ramps and slo mo is also achieved in post. However low frame rates on Varicam can be shot at slow shutter speeds, creating a blurred look of moving subjects. HDCAM slowest shutter speed is 1/24th second.

Motion Portrayal Difference? Once 60i is deinterlaced to form 60p the motion portrayal is exactly the same with both cameras, ie both capture 60 different pictures a second.

Luminance Pixels HDCAM at records 1,555,200 luminance pixels per frame. Varicam at all frame rates records 691,200 luminance pixels per frame. Even when deinterlace HDCAM we still use 777,000 original pixels per frame. 10% more than the Varicam. We interpolate in post to fill in the missing lines.

Both systems need up converting to 1080i. With deinterlaced HDCAM the horizontal res is already at 1080i standard of 1920 pixels but the vertical number of lines has to be doubled in post. To move Varicam to 1080i both horizontal and vertical needs to be upconverted, not only for slomo but for every frame you shoot.

Frame Size In progressive mode each frame from f900 is 5.9 mb in size In Varicam each frame is 1mb.

Native Edit? Native editing (ie maintaining original quality by using firewire) only works if you do not grade or do a mix, otherwise the data is uncompressed altered and recompressed. When edited natively both formats are unreliable and buggy.

On Location A quick slomo shot involves changing tape then changing tapes back and resetting timecode on both Varicam and HDCAM.

Other costs Cost of getting camera, renting decent HD lens tripod and a 1920x1080i online are the same regardless of camera format if you are using a fully fledged post house. DVCPROHD offers savings if you edit natively yourself. If you are shooting a lot of slomo consider having a f900 and a varicam on set.

Still don't understand deinterlace? We shoot 59.97i (interlace) This is 30 frames per second each frame made up of two separate scans of the ccd taken one after the other, first oddlines are scanned then even lines. At no time is there a full scan of the ccd in one pass. Each of these scans is called a field. A TV displays the two fields quickly so you don't notice that the subject has moved slightly between fields nor do you notice that you are only looking at half the lines. A computer can split each frame into its two separate fields so you have 60 separate pictures, each picture missing alternate lines. The computer then fills in the missing lines with an intelligent guess of what it thinks should be there and bingo you have 60 full frames. But the process is time consuming. If you are going to do hours of slo mo its best to do a rough cut or shoot the slomo elements on Varicam or by using the Viper or Sony HDC1500 cameras into SRW1 recorder.

Watch DP Ian Ellis's showreel of 60i deinterlace

Recent quotes from my last three jobs using the SR format

Philips Viper 4:4:4 "the pictures look amazing"

Sony Playstation Aerial 4:2:2 "pictures look superb".

Getty Images Aerial 4:2:2 "simply brilliant"

Note that the Stwo hard drive is capable of 720p recording on location.