Depth of Field Preview

canon400d

I have a canon400d. Can someone please tell me in laymans terms what the figures mean when I depress the Depth of Field Preview button. For example 1/13 or 1/15 or whatever. Also what should the reading be on a low aperture for instance. As you can all well guess I am learning slowly but I am determined to get there in the end.
Kind Regards
Bob

evoryware

http://www.kenrockwell.com/tech/dof-button.htm

[FONT=Georgia, Times New Roman, Times, serif]It's exactly what happens when you squint to see something....[/FONT]
You usually have to let your eyes adapt a little to the darkness. Getting dark is a side effect; it's NOT the purpose of this button.

This pretty much explains it. It does work. The way I tested was to focus on a book 6 ft away and have another book 2 feet away. In Av mode At f5.6 i pressed the button and nothing changed but the words on the book at 2 feet were blurry. At f8 it was a slower shutter speed and it was a bit easier to distinguish the words, but still blurry. At F13 once I adjusted to the light, it was sharp enough to read. f16 sharper still. After f22 it was too dark to be of any use.

The numbers are just the shutter speed and aperture the camera plans on using for the exposure.

HTH

canon400d

evoryware wrote:

http://www.kenrockwell.com/tech/dof-button.htm



This pretty much explains it. It does work. The way I tested was to focus on a book 6 ft away and have another book 2 feet away. In Av mode At f5.6 i pressed the button and nothing changed but the words on the book at 2 feet were blurry. At f8 it was a slower shutter speed and it was a bit easier to distinguish the words, but still blurry. At F13 once I adjusted to the light, it was sharp enough to read. f16 sharper still. After f22 it was too dark to be of any use.

The numbers are just the shutter speed and aperture the camera plans on using for the exposure.

HTH

Thanks ever so much for your advice. I will try this with a couple of books.
Bob

windoze

canon400d wrote:

I have a canon400d. Can someone please tell me in laymans terms what the figures mean when I depress the Depth of Field Preview button. For example 1/13 or 1/15 or whatever. Also what should the reading be on a low aperture for instance. As you can all well guess I am learning slowly but I am determined to get there in the end.
Kind Regards
Bob

ooooh oohh (i know this one "I think" ),

no matter what aperture you select, when you look through the viewfinder, you are always looking at your subject wide open, it isnt until you press the shutter release that you force the blades to move into position.
When you use the Depth of Field Preview button you are looking at what the image will look at the "chosen" aperture.... its a very useful button. yea yea yea i know everything goes dark when you look but its purpose is that you can see the range of DOF in your image if you look carefully. Try it at f/4 and then at f/11 and you will see what I mean. Its also very useful when using a GND.

claudermilk

Yep, that is exactly what is going on, windoze. The lens stays wide open until you actually trip the shutter, this to allow the most light into the viewfinder for helping composition & AF--it's a nice secondary benefit of getting really fast glass. DOF preview is just that, it previews what the film/sensor will see when you trip the shutter & is useful at times.

sirsloop

I find that the DOF button is pretty useless on the rebels... simply because the viewfinder is too small and dark to make good use of it. Sure if you sqint and really look you can see, but I find it much easier to take a photo, review on the LCD, and retake if its not what I was looking for. Perfect reason to get a 1D

canon400d

windoze wrote:

ooooh oohh (i know this one "I think" ),

no matter what aperture you select, when you look through the viewfinder, you are always looking at your subject wide open, it isnt until you press the shutter release that you force the blades to move into position.
When you use the Depth of Field Preview button you are looking at what the image will look at the "chosen" aperture.... its a very useful button. yea yea yea i know everything goes dark when you look but its purpose is that you can see the range of DOF in your image if you look carefully. Try it at f/4 and then at f/11 and you will see what I mean. Its also very useful when using a GND.

Thanks I will try that.
Bob

canon400d

sirsloop wrote:

I find that the DOF button is pretty useless on the rebels... simply because the viewfinder is too small and dark to make good use of it. Sure if you sqint and really look you can see, but I find it much easier to take a photo, review on the LCD, and retake if its not what I was looking for. Perfect reason to get a 1D

Mmmmm so you are saying that the view finder on my 400d is on the small size. I wasn't thinking of a 1d. The price etc etc etc... However, I was planning on getting a 40D what is your views on that please.
Bob

canon400d

claudermilk wrote:

Yep, that is exactly what is going on, windoze. The lens stays wide open until you actually trip the shutter, this to allow the most light into the viewfinder for helping composition & AF--it's a nice secondary benefit of getting really fast glass. DOF preview is just that, it previews what the film/sensor will see when you trip the shutter & is useful at times.

Thanks ever so much. That is certainly worth knowing.
Bob

sirsloop

Find a camera store and get your hands on the camera. I havent held a 40D yet so I cannot comment on the viewfinder. The rebels and the 20/30d VF are quite similar in size, brightness, and information The 20d/30D is nothing compared to a !d viewfinder!

canon400d

sirsloop wrote:

Find a camera store and get your hands on the camera. I havent held a 40D yet so I cannot comment on the viewfinder. The rebels and the 20/30d VF are quite similar in size, brightness, and information The 20d/30D is nothing compared to a !d viewfinder!

Thanks I will do as you say.
Bob

Cason

That button had me puzzled for a little bit. I kept hearing something and I did not know where it was coming from.

When you press the DOF button, look in the lens. You can see the blades close in. Play with the different stops and notice how small the hole is at F22.