DOF tutorial for 35mm adapter users (20 min)

snodart

snodart

Veteran
I made this for a DVD that never happened. Should be helpful for those using or planning to use a 35mm adapter.

It is a bit slow paced, but the info is all there. If the subject is new to you, you might have to watch it a few times for it to "click".

Feedback always welcome :)

Depth-of-Field Tutorial


EDIT (5/15/2007):

The DVD mentioned above was for the Snod35 DIY DVD/kit. Currently, I am no longer planning on making the DVD/kits (you can read why at the link below). However, I have posted a write-up (with pictures) on my website as to how I built the original Snod35:

Snod35 write-up

*Please post any comments and questions about the Snod35 to the thread at the link below*

Snod35 info thread

EDIT (10/14/2007):

You can also view a streaming version (flash) of the tutorial at FreshDV:

http://www.freshdv.com/2007/10/video-tutorial-understanding-depth-of-field.html

or at Letusdirect.com

http://www.letusdirect.com/depth-of-field-tutorial-videos.html

EDIT (01/11/2008):

This is from an older post, but I though it might be helpful to add it here:

Below is from http://www.dvxuser.com/V6/showthread.php?t=71373

 The reason that 1/3” CCD cameras are limited to a long DOF:

 The target size is the size of the physical element that is capturing and recording the image in a given camera. In a motion-picture film camera, it relates to the size of the film. With a DV camera, the target size is the size of the CCD(s) that are recording the image and converting that information into a digital signal. In the case of most miniDV cameras, including the Panasonic dvx-100, the CCD is 1/3". 1/3” does not reflect the actual physical size of the sensor however. The actual width of a 1/3” CCD is somewhere around 5mm wide. Likewise, most 35mm film does not actually have a frame size of 35mm since some of the space is taken up by the perforations in the film and by soundtrack information. The actual frame width of 35mm is often closer to 22mm. So from this, we see that the target size of the 1/3” CCD camera is about 4 ½ times smaller than the actual frame size of 35mm film. What does this mean exactly? Let’s say we are using a lens with a focal length of 50mm for a 35mm film camera and for a 1/3” CCD camera; both of which are at the same distance from the subject.. The images below show how much of the subject each would see.

ccd1.gif



So, in order for the 1/3" CCD to achieve the same subject size in relation to the frame, we would need to do one of two things… either move the camera way back until the subject size is the same in relation to the frame (as compared to the 35mm frame), or use a lens with a shorter focal length. Always shooting from a great distance is not a very practical solution (and technically it lengthens the DOF anyway), so the better option is to use a shorter focal length lens. This would increase our field of view and allow us to obtain the same subject size within the frame... from the same distance as the 35mm camera (or a comparable distance anyway)..

ccd2.gif


This is why prosumer DV cameras have considerably short focal lengths. The Panasonic DVX100B for example has a zoom lens that ranges in focal length from 4.5mm to 45mm. Having a shorter focal length essentially compensates for the very small target size. Since a short focal length inherently creates a long DOF, 1/3” DV cams are limited to a long DOF. You can always back the camera up and zoom all the way in so that the focal length of the DVX is at 45mm. Though technically the DOF would be the same, visually it appears to be much shorter. The reason for this is an whole other can of worms...
 :)

END
 
Last edited:
rock! thanks for sharing man. i know there have to be hundreds of hours of work in that information. much appreciated.
 
I like the way you're presentiing this. It does not, however, let me download it to my computer.
Jgastelb
 
Thanks jgastelb. To download, you need to save the file. For example, if you are using IE and windows: right click and "Save Target As".

[SIZE=+0]Thanks for taking a look. [/SIZE]
 
I don't have a 35mm adapter (yet) but still found it very informative. In fact I was just referencing the video yesterday at a shoot when I was filming from behind the stage, figuring out how to keep the artist in focus while blurring out the audience. It worked perfectly.

Great video!
 
Very well made tutorial, very clear. I don't yet have a 35mm attachment on my DVX but I relish the chance to learn the theory behind it. It's also very kind of you to let us have this video when it clearly must have taken a lot of time and effort to produce.
Thank you,
Philip
 
Snodart probably the best DOF tutorial put together, especially relating to the adapters and equipment we use and I am 100% sure people will use this as a valuable resource. This must have taken a lot of time and I seriously think that your effort to help others understand this is very genorous to say the least.

Then, my biggest issue. Whilst a "in your terms" a short DOF gives a filmic look, many people misuse its purpose. I also think iits very important that people realise the subjective use of say a 35 mm lense and 80mm lense and why one may choose to use both lenses (keeping the subjects at relative size) when shooting the same scene from different angles.

For example a two person shot, I might use a 35mm lense for one angle to one subject and then an 80mm to the subject on the reverse angle (both subjects would be the same size in the frame), the why of that is a very important decision to make when shooting.
 
Thanks for the feedback guys.

ncje said:
Then, my biggest issue. Whilst a "in your terms" a short DOF gives a filmic look, many people misuse its purpose. I also think iits very important that people realise the subjective use of say a 35 mm lense and 80mm lense and why one may choose to use both lenses (keeping the subjects at relative size) when shooting the same scene from different angles.

For example a two person shot, I might use a 35mm lense for one angle to one subject and then an 80mm to the subject on the reverse angle (both subjects would be the same size in the frame), the why of that is a very important decision to make when shooting.
Click to expand...

ncje, I agree for sure. Some tend to think that 35mm adapters are used only to obtain a shallow DOF or a "film look". The fact is though that 35mm adapters allow filmmakers using prosumer DV cameras some of the same artistic options that a filmmaker shooting 35mm film has. In my mind it isn't so much about trying to get DV footage to look like film, but more about taking advantage of the ability to alter the DOF and FOV by using various lenses and settings. With the stock DVX I am limited to 4.5 to 45mm; with an adapter, I can use just about any lens I want. That is an advantage that makes me willing to put up with the various issues associated with using an adapter (light loss, inverted image, dust specs, grain, etc).

The fact that 35mm adapter footage resembles 35mm film more so than straight DV is nothing more than a side effect in my mind. 35mm film has a specific look compared to DV because of its versatility in terms of frame rate, DOF, FOV, etc. Gaining some of that versatility is the true purpose behind 35mm adapters.

Thanks again for the comments all.
 
Haven't seen it yet, on a Mac (osx) it doesn't give you the option of "download file" when your right click. (or control click)
I tried it both on Firefox and Safari. If you let it load all the way, and have Quicktime Pro, then you can "save as quicktime movie" or "save as source".
 
RE1000 said:
Haven't seen it yet, on a Mac (osx) it doesn't give you the option of "download file" when your right click. (or control click)
I tried it both on Firefox and Safari. If you let it load all the way, and have Quicktime Pro, then you can "save as quicktime movie" or "save as source".
Click to expand...

Thanks for pointing this out RE1000. I just fixed the link... you should be able to save the full version now. :thumbup:
 
snodart said:
I made this for a DVD that never happened....
Click to expand...
What do you mean? I've been waiting for this thing since you first started talking about it.

I watched the clip...man that was great. I finally understand all the different components and how they interact with each other to create an image. There have been a lot of great explanations around this board, and I mostly understood it...but seeing the diagrams/images really seals the deal.

Thanks...and I hope you resurrect the DVD project someday ... it was going to show how to build your Snod35, wasn't it?
 
You must log in or register to reply here.
Back
Top