depth of field preview button?

[smittymike19]

what exactly is the DOF preview button supposed to do? when i use the focus button on my rebel, it already shows the dof, why would i need to use the dof preview button. what i see in the lens when it is focused doesnt change when i press the DOF button. ???

[picture-this]

Focus point is not depth of field. You use the depth of field button when you are using any apepture other then wind open to see how much of your shot is in focus. The reason for this is because the lens only stops down to the selected apeture right before taking the picture because wide open flows the most light through the veiwfinder. Stop down to something like f8 and see that alot more of the picture infront of and behind the focus point is sharp and that the viewfinder is way darker sometimes too dark to compose a picture. Sorry I am bad at explaining but figured Id try.

[smittymike19]

ok, i just did it. and i swear i cant tell the difference. maybe i need to do it outside looking at a long landscape shot? i dunno, maybe i need my eyes checked, cause it just gets darker. tahnks for your help though, your explanation makes perfect sense, i just cant see the difference.

[tim]

It gets darker which makes it's effect more difficult to see. It shows what the DOF will be when the lens stops down to take the photo - when you're looking thru the viewfinder it's always at the lenses max aperture.

[Incomplete Pete]

The DOF Preview button is very useful! Especially when doing group photos, you set the aperture then just press the button to make sure all the faces are sharp! It's a subtle but useful tool.

[picture-this]

Ah ok, maybe you don't have a lens with a fast apeture so it's a bit harder to notice, so focus on somethign somewhat close as the closer you focus the shorter yoru depth of field will be and maybe change it to a larger f#. Now that I have explained how it works. I am kinda in the same boat as you as I use the depth of field button and everything looks like the depth of field is just what I want through the viewfinder and then when I check the pics out after it's not what I wanted. I find it really hard relying on the eye, does anyone have any tips? I don't want to carry around a big briefcase of depth of field charts with me...

[csondagar]

I have similar viewing issue as does smittymike19. I cannot see anything different between the results of pressing DOF Preview and half-pressing the shutter release buttons. :confused:

[PhotosGuy]

Try f/22

[Incomplete Pete]

Point the camera up at a light fitting, then, regardless of the darkness, you'll see the joys the DOF button brings!

[2goldens]

At first I didn't see what the DOF did. Now when I take photographs of groups or something I use it most of the time. As you start to discover all the little things that go along with your Digital Rebel you will see that it has all you will need to start shooting some great pictures. As you get more advanced in your photography you may need to get a new camera. That will be down the road. Just keep discovering your camera. You will love it.

Have Fun

Anthony

[jimsolt]

In an SLR camera, the lens is normally wide open for better viewing in the viewfinder. When you push the DOF button, you stop the lens down to the actual aperture you will use when you take the picture.
If the actual lens aperture is close to wide open, you won't see much if any difference with the DOF button. If the lens is stopped way down, you will see the difference including the depth of field. When you see this difference you will also see sometimes that any detail in the viewfinder is difficult to see because you have limited the light coming in. That's why it is normally opened up for focusing, etc.
Jim

[Raj]

In an SLR camera, the lens is normally wide open for better viewing in the viewfinder. When you push the DOF button, you stop the lens down to the actual aperture you will use when you take the picture.
If the actual lens aperture is close to wide open, you won't see much if any difference with the DOF button. If the lens is stopped way down, you will see the difference including the depth of field. When you see this difference you will also see sometimes that any detail in the viewfinder is difficult to see because you have limited the light coming in. That's why it is normally opened up for focusing, etc.
Jim

Very clear explanation Jim.
Thanks

[Jon]

If you want to see the DoF button in action, put the 50 f/1.8 on, and set your aperture to f/22 on a fairly close-in subject with stuff in front and in back of it. Looking at a bookshelf or a fence from about a 45 degree angle would be good. Take a good look (and maybe even a picture) wide open, then repeat at f/22 using the DoF button to stop the lens down. You can also take a picture here (if there's enough light - a slow shutter speed will give you camera shake, confusing the issue).

[smittymike19]

If you want to see the DoF button in action, put the 50 f/1.8 on, and set your aperture to f/22 on a fairly close-in subject with stuff in front and in back of it. Looking at a bookshelf or a fence from about a 45 degree angle would be good. Take a good look (and maybe even a picture) wide open, then repeat at f/22 using the DoF button to stop the lens down. You can also take a picture here (if there's enough light - a slow shutter speed will give you camera shake, confusing the issue).
im gonna mess around with it this weekend when i get soem time. thanks for teh help..ill psot to let you know what i discover :)

[byso]

This was something I also needed to understand.....

Thanks.

[csondagar]

Makes sense to me now, and can actually see the difference. Thanks to all for your great explanations.

[Longwatcher]

Makes sense to me now, and can actually see the difference. Thanks to all for your great explanations.

I cheated when I tried to learn DoF, I downloaded the DoF charts from the Canon Museum pages for the various lenses I have

http://www.canon.com/camera-museum/index.html

http://www.canon.com/camera-museum/camera/lens/f_lens.html
At the bottom of each lens page is the DoF data.

Previously it was just too hard for me to use the DoF preview button. With newer camera it is a bit easier to use, so I use it on occasion when I need to confirm in advance.

[hmhm]

Put your fastest lens on the camera, put the camera in Av mode, hold down the DoF preview button and dial through the apertures. Do this looking through the viewfinder, outdoors on a bright day, with the camera focused on something nearby (i.e. fill the viewfinder with something small).

Also do this with the camera pointed at yourself, while looking into the "business end" of the lens, again dialing through the apertures. You'll notice the lens' diaphragm opening and closing as you dial in different apertures with the DoF preview button held in. Ordinarily, the lens' diaphragm is wide open, it gets shut to the appropriate value for a split second when the exposure is made, then opens back up again. If you hold in the DoF preview button, though, it closes the diaphragm down to whatever aperture you have dialed in and leaves it there (which is sort of the definition of what the DoF preview button does).
-harry

[Cadwell]

I never have much use for DoF preview button, unless of course I am somewhere dark. Then, if you have an external flash on the camera, pressing the DoF preview button makes it strobe at high speed for a few seconds. This can make quite an effective flashlight/torch for finding dropped CF cards etc, and is also quite useful for scaring those around you. :p

[robertwgross]

Don't laugh, Cadwell.

I had to do that one time in a mine tunnel.

---Bob Gross---