2/3" vs 1/2" ccd chips

[Tim Allison]

We are about to jump on the XDCAM bandwagon. When we looked at the F350 camera, I was really surprised at how unforgiving the camera was on focus issues. If you are the tiniest bit soft on your focus, the picture clearly showed it.

2/3" cameras are supposed to give greater depth of field than 1/2" cameras. This may be an impossible question to answer, but how much is this going to help when shooting? My assumption is that greater depth of field will give you a little bit more margin for error on your focus.

I don't really understand the physics of why a 2/3" chip gives greater depth of field than a 1/2" chip. Instead of a science lesson, can someone give their practical experience on the difference (if any) on shooting with cameras with the two different pickup chips?

[Nate Weaver]

Actually Tim, it's the other way around. The larger the chips, the shallower the DOF, in turn making acceptable focus more difficult.

In other words, if you have trouble with a 1/2" camera, a 2/3" will be the same problem except slightly worse.

HD is just unforgiving when it comes to focus...it's probably the biggest thing to learn as a shooter new to the format.

[Tom Hardwick]

Nate's right. The 2"/3 16:9 chip has double the surface area of a half inch chip, making it more light sensitive and offering you far more scope for differential focus and pull focus games. Mind you, with a proper viewfinder you'll have no trouble in getting accurate focus, and such big chips are much happier workinng at small apertures than (say) 1"/3 chipped camcorders are.

tom.

[Mike Favazza]

Tim,

A 2/3" CCD gives you the potential to REDUCE depth of field, all else being
equal.

A 1/2" camera lens gives you the ability to INCREASE DEPTH OF FIELD.
(The 1/2" camera gives you GREATER DEPTH OF FIELD, assuming the
word "greater" means "more."

Imagine you've chosen a focal length that gives you the same sized head shot with a 2/3" camera and a 1/2" camera--and you're
using the same f-stop and distance between camera, subject and background.

The head shot needs a LONGER FOCAL LENGTH on the lens of the 2/3" camera to get that same sized head to fill the 2/3" ccd.

Practical example: The 2/3" camera's lens is photographing a close-up of a talking head (with a 5-degree angle of view)

That 2/3" camera close-up requires about a 101mm lens to achieve that certain sized head.

The same sized head shot with a 1/2" chip camera will require approx. a
73mm lens.

All else being equal, the 73mm lens inherently gives you more focus than
the 101mm lens.

So the longer lenses on the bigger-chip cameras will help you REDUCE DEPTH
OF FIELD.

Bigger chips = longer lens to achieve same-sized shot
Longer lens = less depth of field (sharp-focus area reduced)

2/3" = less depth of field
1/2" = more (greater) depth of field

Ther terminology gets confusing.

Good luck

[Alister Chapman]

It's my experience that it in general it is harder to get pin sharp focus on cameras with smaller CCD's during every day shooting. As has been said smaller CCD's mean greater depth of field. Because of this I find that the difference between being spot on in focus and very slightly out of focus is easier to see with a 2/3 inch camera, so as a result I find it easier to get focus spot on with bigger CCD's. The F350 has a good viewfinder with a very wide peaking range. I tend to have the peaking turned up quite high as you can see the pin sharp focus point more easily.

HD is very unforgiving when it comes to focus. With an HD head and shoulders shot you can tell whether a persons ears, eyes or nose is in focus and it's distracting when they are not, with SD you would not have this sharp differentiation between the nose and ears it would just be a face that is either in focus or not.

[Tom Hardwick]

It might also be worth pointing out that lenses designed to cover the 2"/3 chip are a lot bigger, heavier and more expensive than those designed for the smaller 1"/2 chip.

[Greg Boston]

Originally Posted by Tom Hardwick

It might also be worth pointing out that lenses designed to cover the 2"/3 chip are a lot bigger, heavier and more expensive than those designed for the smaller 1"/2 chip.

We also need to point out that in Sony's pre-NAB press release, they revealed something that I didn't know and it explains the exceptional performance of this camera. They are using the entire surface area of the 1/2 chip which in reality, makes it somewhat larger than a true 1/2 camera but still less than a 2/3 camera.

On paper, there is a difference. In reality, the F330/F350 have been delivering performance that surprises everyone in terms of shallow dof and latitude.

-gb-

[Bob Willis]

Greg,
What exactly does that mean, that they are using the entire surface of the 1/2" chip? Why wouldn't they use the entire surface in the first place.

[Greg Boston]

Originally Posted by Bob Willis

Greg,
What exactly does that mean, that they are using the entire surface of the 1/2" chip? Why wouldn't they use the entire surface in the first place.

On most imagers, there is an area of inactive pixels surrounding the active pixels. A black border if you will. You will often see specs quoting total pixels and active pixels. Sony is saying that they used the entire surface of the 1/2 imager for their active pixels.

This more or less explains how they are maximizing the performance out of a 1/2 camera and the end results seem to prove it.

For the foreseeable future, the cameras will use ½-inch CCDs, but a 2/3-inch XDCAM HD camera is planned for some time in 2008. [Sony said their current ½-inch imagers use the entire surface area, making them comparable in acquisition quality to others’ 2/3-inch CCDs.]

-gb-

[Tim Allison]

I've learned something today. Back when we had our f350 demo for a week, all of of were very surprised at how easy it was to mess up a shot due to "slightly" soft focus. It doesn't help that my nearly 50-year old eyes don't seem to focus as well either. :)

I guess that paying much closer attention to focus is one of the things that I will learn to do.

[Bob Willis]

Originally Posted by Greg Boston

On most imagers, there is an area of inactive pixels surrounding the active pixels. A black border if you will. You will often see specs quoting total pixels and active pixels. Sony is saying that they used the entire surface of the 1/2 imager for their active pixels.

This more or less explains how they are maximizing the performance out of a 1/2 camera and the end results seem to prove it.



-gb-

If you design certain lenses for a 1/2" image area and completely different lenses for a 2/3" image area I don't understand how the image area could be bigger than 1/2". Are they using more active pixels to gather more information from a 1/2" image area? Just curious.

[Louis Mostert]

Originally Posted by Greg Boston

We also need to point out that in Sony's pre-NAB press release, they revealed something that I didn't know and it explains the exceptional performance of this camera. They are using the entire surface area of the 1/2 chip which in reality, makes it somewhat larger than a true 1/2 camera but still less than a 2/3 camera.

I hope this is the case with the new Sony XDCAM EX 1/2" (the small handheld one) that they showed at NAB 2007.

[Greg Boston]

Originally Posted by Bob Willis

If you design certain lenses for a 1/2" image area and completely different lenses for a 2/3" image area I don't understand how the image area could be bigger than 1/2". Are they using more active pixels to gather more information from a 1/2" image area? Just curious.

This may also help to explain a statement made by the tech at my local Fujinon repair facility. He said my 1/2 lens is identical construction to the 2/3 lens from the flange forward.

Keep in mind, the only 1/2 HD cameras I know of at present are the XDCAM HD cameras. Fujinon's website has a separate lens category listing for XDCAM HD. This may be why...because it's not a true 1/2 target.

-gb-

[Thierry Humeau]

Originally Posted by Tom Hardwick

It might also be worth pointing out that lenses designed to cover the 2"/3 chip are a lot bigger, heavier and more expensive than those designed for the smaller 1"/2 chip.

I don't quite agree with this. We have Canon's latest HDGc series for both, 1/2" and 2/3" CCDs and they look and weight exactly the same.

Thierry.

[Thierry Humeau]

Originally Posted by Tim Allison

I've learned something today. Back when we had our f350 demo for a week, all of of were very surprised at how easy it was to mess up a shot due to "slightly" soft focus. It doesn't help that my nearly 50-year old eyes don't seem to focus as well either. :)

I guess that paying much closer attention to focus is one of the things that I will learn to do.

I have been shooting for 20 years, and now doing most of my work in HD. That is indeed the most challenging side of it, sharp focus. It is especially tricky when you like shallow focus and work at or close to full aperture. When shooting a subject tight, just choosing the tip of the nose instead of the eyes as a focus point can yield undesirable results...

Thierry.