maximising depth of field? limit of dslrs for video
 

so id really like to replace my last tape based video camera for weddings with another gh2, problem is this camera is used as like a long far away static shot at weddings and having everything in nice focus the entire range of the shot is important. Problem is, inside churches im wide open at like 1.4, so depth of field is super narrow. What i dont get is how my canon xl h1a can be wide open at 1.6 and still have everything in focus"!

Re: maximising depth of field? limit of dslrs for video
 

f-stop is only one thing that affects depth of field. The sensor size and focal length is also a factor. In this case the small 1/3" chips of the A1 is what's giving you lots of depth of field... the wider the shot, the more depth. Do some searching on "hyperfocal distance"

Re: maximising depth of field? limit of dslrs for video
 

To sum up:

Shallow depth of field means less in focus.

All others being equal:
Large aperture (low F number) equals shallow depth of field.
Large focal length (or more zoomed in) equals shallow DOF.
Larger sensor equals shallower DOF.

So to get the greatest DOF (most in focus), use a small aperture (high F number, which menas more light), a wide lens, and a small sensor.

Re: maximising depth of field? limit of dslrs for video
 

ah well i was aware of all of those but how the sensor size effected it! so it would seem this is not an issue i can simply work around with my gh2, thats rather unfortunate. hm well looks like I may be sticking to my tape based camera a bit longer!

Re: maximising depth of field? limit of dslrs for video
 

This is not true. Calculate your lens and camera's hyperfocal length and everything will be in focus from that point to infinity. There's app for it even. Google it.

Re: maximising depth of field? limit of dslrs for video
 

A far away static on a wide angle is going to create very few, if any, DOF problems. I'm sure you could shoot slower than F1.4, by throwing in a light for a bit more exposure just to be sure.
Anywhere up to about a 14mm should be fine.

Re: maximising depth of field? limit of dslrs for video
 

Well I found some calculators, that is pretty helpful. I just didn't think so much about infinity side of focus, as the calculators want to give that specific 2-3 feet range that will be in focus.

Re: maximising depth of field? limit of dslrs for video
 

Stopping down and/or using the hyperfocal distance is your best bet. Maybe you might want to look at the GH3 or 5D Mark III, which will give you that extra ISO push for more DOF.

Here's a great resource on understanding DOF: DOF and DOF2

Re: maximising depth of field? limit of dslrs for video
 

Here's another idea, you can use the EX TELE mode (ETC) in combination with a wider lens. (This mode uses the center 1920x1080 pixels of the sensor) I believe the crop factor is 2.6x for 1080 mode.(3.1x for 720p) So you could take a situation where you would normally use a 35mm lens, put on a 14mm lens, and enable ETC mode. This should give you about the same field of view as the 35mm, but with the depth of field of the 14mm. Of course you can only go as wide as available lenses in the required max aperture allow. If you need F2 or faster about 12mm (31mm ETC equiv) is the widest lens I know of. Or if F4 is fast enough the 7-14mm lens (18-36mm ETC equiv) would be a good option. Just throwing some theories/ideas out there, hope this helps!

Re: maximising depth of field? limit of dslrs for video
 

According to this tutorial, sensor size does NOT affect DOF.

Re: maximising depth of field? limit of dslrs for video
 

Wow once again a ton of helpful information. Thank you both :)

Re: maximising depth of field? limit of dslrs for video
 

Sure about that? A 5DII can provide a shallower dof with the same lens compared to a t2I and there is a reason why you can't achieve the same shallow dof on small sensor camera's. I"d say that sensor size definitely has an impact on the dof.

Re: maximising depth of field? limit of dslrs for video
 

I didn't watch the tute but if that's what it says then it's not accurate.

Sensor size most definitely impacts DOF.
While you can certainly get shallow DOF with a small sensor camera using long lenses, large apertures and proximity, A BMC with will never remotely get the kind of shallow DOF that a full sensor 5D will get with the same lens.

I'm actually amazed that someone would make a tutorial with that. Why does he think that traditional 1/3" sensor video cameras needed spinning glass adapters to achieve shallow DOF?
It's because they have small sensors.

Re: maximising depth of field? limit of dslrs for video
 

With everything else staying the same, just changing the size of the sensor, or the area of the sensor used, will have no effect on the depth of field. The light that falls on the physical plane of the sensor is exactly the same, just a different crop of the same image. However, to fill the frame/sensor area with the same angle of view, you either need to adjust the distance to the subject, or the optical formula of the lens (use wider lens etc.). Either of these adjustments will change the DOF.

Re: maximising depth of field? limit of dslrs for video
 

Because we have "everybody and his brother" making "tutorials" whether or not they have the knowledge/experience to draw from.

Re: maximising depth of field? limit of dslrs for video
 

The guy has plenty of knowledge and experience to draw from. Check out his website and watch his vids. This isn't some knucklehead with a Sony Handycam spouting off.

Re: maximising depth of field? limit of dslrs for video
 

You may want to watch it before discrediting the information that you think may be in it from second hand hearsay. The information in the video is accurate. The statement "Sensor size does not change the DOF" is also accurate.
If you watch the video he explains as I have that all else staying the same, it only changes the FRAMING(or Crop). You are correct though that to achieve the same DOF with the same FRAMING would be more of a challenge with a smaller sensor due to the changes needed in lens focal length/aperture. Changing the distance can also compensate, but then you are changing the perspective, which would not reproduce an identical image.

What would be the solution to all this? An converter/adapter that fits between the lens and the body (similar to the teleconverters that are available) that optically compensates for the crop size of the sensor, adjusting the image circle of the lens to fall on the sensor in the same proportions as the original comparative example. This would also have the positive effect of an increase in light density equal to the factor of the converter.
Example, GH2 with 50mm FD mount lens and M4/3 adapter, 2x crop sensor. Create a micro 4/3 adapter with optics inside that would make it a .5x converter, Now you have the same framing as a full frame sensor because you are using the full image circle of the lens instead of only the center half, and you have also gained a stop of light (2x factor increase in light).
From what I remember reading, this is very possible, but was patented by a company (Kodak I believe) and therefore Panasonic/Olympus or third party manufacturers are blocked from producing it.

Re: maximising depth of field? limit of dslrs for video
 

I would never call him names. I just said that claiming that sensor size doesn't impact DOF is inaccurate, and stated why in my experience. Lot's of things, foreground background proximity, iris, focal length and yes sensor size all directly impact DOF.

It's just physics, not a debate. Like I said, I didn't have time to watch the tute but here's the simple point. In order to get anything close to shallow DOF on say an "old school" DV camera like the XL1 or XL2 you would need to shoot very long - 300, 400mm or more, and have your foreground and background very separated.

Even then, in all but the largest interiors it just won't work practically. In other words, in the only sense that matters - practical production, the smaller the sensor, as we shoot them, the more difficult it is to get shallow DOF with a common lens in a common setup.

So while theoretically he may make sense, practically, if there were no difference, there never would have been Letus and P&S Mini 35s, and the 5D revolution wouldn't have meant what it did.

That's my opinion with no ill will toward the OP or person who made the tute.

Re: maximising depth of field? limit of dslrs for video
 

All I can do to add to this interesting discussion is that on the GH3 (and probably on the GH2), there is no functional difference in DOF between shooting HD, shooting EX. Tele or shooting a full frame still with the same lens.