Question about DSLRs and focusing...

Sithxace

Sithxace

Well-known member
I have a Canon XHA1 for my company and I am choosing between buying a better camcorder or to go DSLR. What we shoot, we are moving around a lot so my concern is keeping the object in focus and i move closer and further away.

My question is, if I get a Canon 60d, close the aperture as much as possible like 7.1 and up with a slower shutter speed, will the object still be in focus if I move a few steps closer or further away?
 
It depends. A super wide lens will allow you to get a much greater depth of field.

For example:

Canon 60D
Iris= 7.1
Distance = 10 feet

if lens = 16mm ==> DoF = infinity
if lens = 24mm ==> DoF = 28 feet
 
Depth of field works the same on every camera. It's a function of the lens in relation to the sensor size. If you buy a better camera you'll probably be getting a larger sensor area, meaning the focusing would be about the same. The only difference is that the lenses you can use aren't optimized for video type focus throws. A good follow focus on a rig takes care of that. If that's your main concern it really shouldn't be. This isn't a huge sensor like the 5d, and if you have any experience with DSLR photography you know what to expect. If you don't have any experience with that then I would recommend borrowing a camera.

Your main concern should be ergonomics and how the camera's features fit in with your needs and workflow.
 
Cassius said:
Depth of field works the same on every camera. It's a function of the lens in relation to the sensor size.
Click to expand...

Both statements are incorrect.

To save a lengthy explanation right here, please either Google for a detailed explanation or refer to Wikipedia.

Here, I just would like to point out that

ASSUMING EVERYTHING ELSE (frame/composition, lens, aperture, distance, etc) BE THE SAME, merely enlarging a DSLR camera's sensor will actually tend to INCREASE the DOF. This is completely opposite to the commonly held belief (misconception) that as compared to a camera like 60D, 5D yields a more shadow DOF due to its larger sensor size (as if increasing the sensor size would reduce DOF).
 
You can't retain frame, lens, aperture, AND distance while switching the sensor size. That's the point. Switch the sensor and retain the distance, you change the frame. Switch the sensor and retain the frame, you switch the distance.
 
The nature of what im shooting, i will shoot low angles so I was gonna buy a rig for it to allow me to do so. I wont be able to keep something in focus at this angle so thats why I wanna see if its practical to close the Iris as much as possible that itll allow me to rock back and forth a few feet but keeping the the subject in focus.
 
If you have enough light, definitely. But you'll need to stop down to F8 at the widest to be totally reliable. The actual number depends on your distance from the subject.
 
henryqiu said:
Both statements are incorrect.

To save a lengthy explanation right here, please either Google for a detailed explanation or refer to Wikipedia.

Here, I just would like to point out that

ASSUMING EVERYTHING ELSE (frame/composition, lens, aperture, distance, etc) BE THE SAME, merely enlarging a DSLR camera's sensor will actually tend to INCREASE the DOF. This is completely opposite to the commonly held belief (misconception) that as compared to a camera like 60D, 5D yields a more shadow DOF due to its larger sensor size (as if increasing the sensor size would reduce DOF).
Click to expand...


Thats not true at all.

If you keep the focal length, aperture and distance from the subject the same and change from an APS-C to a full frame the depth of field will stay exactly the same and the field of view will be wider.

If you keep the focal length, aperture and field of view/framing the same and change from an APS-C sensor to a full frame the depth of field will become shallower.

A simple way to think of it is by imagining the crop tool in photoshop. Take an image from a full frame sensor. Now to relate that to an APS-C for example, you merely need to crop the full frame image by 1.6x and there you have it.

This isn't my image but it explains it very well..

fullframeversusapsc2.jpg
 
You must log in or register to reply here.
Back
Top