Hyperfocal for zoom calc for DoF challenge

Canon EF-S 18-55mm f/3.5-5.6 IS

06/04/2004 10:09:39 AM · #2

The calculator you have will work fine. If you'll have your Palm with you, just put in what you think the actual focal length of your zoom length currently is (using the scale on the lens).

Message edited by author 2004-06-04 10:10:02.

Konador

Canon EOS-500D Rebel T1i

06/04/2004 10:14:40 AM · #3

Do you have to take into account the 1.6 crop factor when putting in the zoom length, or is this irrelivent?

EddyG

Canon EF 28-135mm F/3.5-5.6 IS USM

06/04/2004 10:20:24 AM · #4

When using something like this online calculator (and presumably the Palm software by the same guy), you enter the actual focal length of the lens, not the "35mm equivalent".

BikeRacer

Canon EOS-300D Rebel

06/04/2004 10:23:00 AM · #5

EddyG - Thanks!

Konador - I think the calc takes that into account by using a different estimate for the circle of confusion for the sensor. Or, I could be totally wrong... :^)

dacrazyrn

Nikon D300

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

06/04/2004 06:11:30 PM · #6

did you download one called pCam? That one lets you set up your lenses and the f factor , circle of confusion and everything.

BikeRacer

Canon EOS-300D Rebel

Canon EF 28-135mm F/3.5-5.6 IS USM

06/04/2004 06:34:30 PM · #7

Originally posted by dacrazyrn:

did you download one called pCam? That one lets you set up your lenses and the f factor , circle of confusion and everything.

I think what I d/l was called DOFMaster. Will look out for pCam though.

06/04/2004 09:36:33 PM · #8

Originally posted by BikeRacer:

I took some landscape photos yesterday using 28-135mm and 18-55mm both at the widest end on A-Dep mode. Each time I pressed the shutter button halfway, the fstop and shutter speed changed and I picked the one with the biggest fstop number in this case 3.5 (for both lenses). The shutter speed will then change to some higher number like 300 or higher and that seems to get deep dof.

I also tested the dof preview on the side of the camera. I was told that when looking thru the viewfinder and this button is pressed, the scene will darken when the dof is shallow. The level of darkness will depend on how shallow the dof is. If there's no change at all, then you've achieved a deep dof.

Anyone care to correct me or have the same experience?

wewillexplore

Canon EF 24-105mm f/4.0L IS

06/04/2004 09:38:13 PM · #9

Now, I could be wrong (again) but isn't 3.5 a fairly NARROW dof not a large DoF?

Or am I wrong again?

scalvert

Canon EOS-5D Mark III

06/04/2004 09:47:20 PM · #10

Originally posted by bruchen:

I also tested the dof preview on the side of the camera. I was told that when looking thru the viewfinder and this button is pressed, the scene will darken when the dof is shallow. The level of darkness will depend on how shallow the dof is. If there's no change at all, then you've achieved a deep dof.

Actually, the reverse is true. The Rebel's viewfinder is always open to the largest aperture to allow as much light in as possible for composing your shot. Pressing the DOF Preview button will quickly stop down the aperture so you can see the true depth. As Mavrik suggested, deep DOF is achieved with small apertures... f/11 to f/22 and beyond. Since the aperture (opening) is small, less light is allowed in and the scene will appear MUCH darker when previewed. If there's no change at all, then you're still at the largest aperture and you'll get a shallow DOF.

06/04/2004 09:49:15 PM · #11

Originally posted by mavrik:

Now, I could be wrong (again) but isn't 3.5 a fairly NARROW dof not a large DoF?

Or am I wrong again?

3.5 is the largest fstop number on the two lenses i referred to.

large fstop number = narrow dof = more blur :)

wewillexplore

06/04/2004 10:00:37 PM · #12

Ok, but in the challenge, we are going for NO blur, right?

Message edited by author 2004-06-04 22:01:13.

06/04/2004 10:07:56 PM · #13

Originally posted by scalvert:

Originally posted by bruchen:
I also tested the dof preview on the side of the camera. I was told that when looking thru the viewfinder and this button is pressed, the scene will darken when the dof is shallow. The level of darkness will depend on how shallow the dof is. If there's no change at all, then you've achieved a deep dof.

Actually, the reverse is true. The Rebel's viewfinder is always open to the largest aperture to allow as much light in as possible for composing your shot. Pressing the DOF Preview button will quickly stop down the aperture so you can see the true depth. As Mavrik suggested, deep DOF is achieved with small apertures... f/11 to f/22 and beyond. Since the aperture (opening) is small, less light is allowed in and the scene will appear MUCH darker when previewed. If there's no change at all, then you're still at the largest aperture and you'll get a shallow DOF.

Before this challenge, I've never used the A-dep mode on the Rebel and whenever I wanted a deep dof, i just used a f11 or higher, even f36 depending on the lens.

I have an image at 1/500 f3.5 and everything is in focus, foreground and background elements. Couldn't post it cuz i might submit it for the challenge.

This is probably explained by hyperfocal distance (which I know nothing about) but I will quote John Setzler from his exposure tutorial on page 19.

Taking advantage of the hyperfocal distance can help you out in several ways. When photographing wide-angle scenes where your objective is to have everything in sharp focus, you would normally use the smallest aperture possible for the photograph. The small aperture gives you the greatest depth of field. However, you may still have objects in your image that are out of focus or soft because they are close to the camera. The reason for this is that your point of focus is far away. When your focus is way out in the distance somewhere, your near focus distance is farther away as well, so closer objects in your scene may appear soft or out of focus.

Another advantage of using the hyperfocal distance is that you may be able to work with a larger aperture and faster shutter speed while keeping everything in your image in focus. In the above calculation using 28mm and an aperture of F16, let's assume that our shutter speed for proper exposure is 1/60. If you are shooting a landscape where there is a bit of a breeze, you could possible get some motion blur on the tree leaves or in the grass at that shutter speed. If you could shoot the same scene at F8 and a shutter speed of 1/250, you will greatly reduce the chances of blur in your image. Using the above calculation, our hyperfocal distance for 28mm at F8 would be 16.1 feet. This means that if we focus on something 16 feet out, we will have sharp focus from 8 feet to infinity. If there is nothing within our composition inside of 8 feet, we could change apertures, get a faster shutter speed, and still keep everything in focus.

Edit: typo error corrected, bad typist.

Message edited by author 2004-06-04 22:11:28.