Depth of Field check button

[SSonnentag]

I have read and reread the short description in the manual on how the DEPTH OF FIELD CHECK BUTTON works, but I'm still clueless. :) Could someone please explain its function in words an amateur can understand? Thanks.

Shawn

[ncphotoman]

When you depress the depht of field preview button on most cameras is simply closes the aperature of the lens to the f-stop you have selected - be it f5.6 or f16. The tighter the setting the darker the view due to the constriction of light, but the sharper the overall image in the view finder. It is a tool that allows you to see how much of your image will be in focus. After a few thousand rolls of film or a few gigs of data you will more than likely never use this feature again. I use it on rare occasions when it is critical, but experience will over take and this will become second nature to you based on the subject matter you are photographing. Hope this answered your question.

[Tom V]

The depth of field is the area in front of, and behind the plane of focus (usually the subject of your image), that looks sharp. When a lens aperture is open (ƒ1.4, ƒ2, ƒ2.8, etc.) the depth of field is shallow. When a lens aperture is smaller (ƒ8, ƒ16, etc.) the depth of field becomes deeper. For example, with a 50mm lens focused on a subject 7 feet away, and the aperture set to ƒ2.8, everything from 6.5 feet to 7.6 feet may be considered sharp, objects outside of that range can be considered "out of focus" because the image has a "shallow depth of field." Stop the lens down to ƒ22 and everything from 5 feet to 20 feet may look sharp enough to be considered "in focus" because of the "deep depth of field."

Cameras can only focus on one plane, and only things on that plane are truely in focus. With a view camera, the photographer can shift or tilt the plane of focus with the camera controls. There are Nikkor lenses that have tilt and shift features for changing the plane of focus as well. Generally, with ordinary cameras and lenses, the film plane, the lens plane and the focus plane are all parallel.

The reason you would use a Depth of Field button is to check your image's depth of field. When you look thru the viewfinder, the lens is wide open despite what the aperture is set to close down to when you take the picture. The instant you trip the shutter, the lens closes down, the mirror raises, and the shutter opens for the exposure. After the exposure, everything resets, including the aperture. So generally you never see how the depth of field will look while looking through the viewfinder - unless - you are shooting at maximum aperature, or you use the depth of field button.

When you press the depth of field button, the lens aperture closes down to the size that it will be during the exposure. The more it closes, the deeper the depth of field, and the darker the viewfinder image. You can then check your (darkened) image to see what the depth of field will do to your composition.

For example: Shooting a baseball game through a chain link fence. Your telephoto lens is set to ƒ8 and is focused on a player on the field. You look throught the viewfinder and the fence is so out of focus you can hardly see it (the fence) because the lens is currently wide open. You think the out of focus fence is acceptable and maybe even a little artsy. Press the depth of field button and the lens stops down to the shooting aperture (ƒ8), the viewfinder darkens, but you can see that the fence pops into apparent focus. Yuck! You then decide to not shoot, you can move closer to the fence (so it is out of the depth-of-field), or shoot over or around the fence. Lucky for you, you brought your wire cutters and remove the fence.:p

Wide angle lenses have more apparent depth of field than do telephoto lenses. The depth of field also increases the farther away you are focued. With a Macro (Micro) lens, focused 5 inches away, depth of field may only be 1/4 inch wide open, and 3/4 closed down. With a 20mm wide angle lens, focused at 4 feet, at ƒ11, everthing from 2 feet to infinity is in the depth of field and will appear in focus. This is handy if you are shooting a distant mountain and want the foreground flowers in focus too. If you focus on the mountain at ƒ11, everything from 4 foot to way past the mountain will look sharp. Instead of focusing on the mountain, set the focus to 4 feet, and you will get everything from 2 feet fo infinity in focus. You can check this effect with the depth of field (preview) button.

[SSonnentag]

Thanks so much, tom! That actually makes sense and I think I can start to use the button now. :)

Shawn