Just an assumption about dof

[Marksjones]

Sorry for the basic questions but just trying to understand the dof thing a little better

When I set the Nikon 5700 into Aperture priority mode are the following assumptions correct?

1) If I use a larger F stop then my pictures will have more depth of field?

2) Assuming I set the F stop higher and therefore, less light comes into the camera and you have more dof: Will the Nikon be trying to lower the Shutter speed to allow more light in?

3) I get confused with point 2 as the camera seems to lower shutter speed to let more light in wont that affect the dof and the brightness of the pic.

Any comments welcome...

thanks
Mark..

 

[Jose Luis]

Please read this:

http://forums.dpreview.com/forums/read.asp?forum=1007&message=4164282

http://forums.dpreview.com/forums/read.asp?forum=1007&message=4164741

http://forums.dpreview.com/forums/read.asp?forum=1007&message=4165025

--
=======
JL

 

[kecohen]

Sorry for the basic questions but just trying to understand the dof
thing a little better

When I set the Nikon 5700 into Aperture priority mode are the
following assumptions correct?

1) If I use a larger F stop then my pictures will have more depth
of field?

Yes, the larger the number, the smaller the aperture, the greater the dof.

2) Assuming I set the F stop higher and therefore, less light comes
into the camera and you have more dof: Will the Nikon be trying to
lower the Shutter speed to allow more light in?

Yes, it will slow the shutter 1 stop to give you the correct exposure.

3) I get confused with point 2 as the camera seems to lower shutter
speed to let more light in wont that affect the dof and the
brightness of the pic.

Shutter speed has little relevance to dof. It will affect the brightness of the picture, though, yes. But if you are using a flash the camera will increase the shutter speed to accomodate the increased light. Assuming your subject is in flash range, you will get the proper exposure. If the subject is beyond flash range it's possible to get an even worse underexposed frame than if you didn't use the flash at all.

If you're not using a flash, you may compensate in one of two ways, increase your ISO, or use EV+. Although, in general, if the whole photo is underexposed 1 to 2 stops, it may be more advisable to increase ISO as exposure compensation can muddy your colors as well as add noise.

--
Karen

...but if you try sometimes, you just might find, you get what you need.
Minolta 7000i, accessories and lenses, lenses, lenses; CP5700, TC15ED,
Kenko KUT-300 Hi, SB80X Speedlight, Epson Stylus 980N, Epson 7600
(shared), Epson Expression 1680 w/ transparency unit, Tamron Fotovix
60WU....
http://www.e-designarts.com
http://www.pbase.com/kecohen/

 

[Greg Matthews61547]

depth of field is related solely to the focal length of the lens, the subject to lens distance, and the aperature (F-stop). it has nothing to do with the actual amount of light, or the shutter speed.

if you want MORE DOF, move FARTHER AWAY, or use a SMALLER F-Stop (higher number), or a lens setting with a LOWER focal length.

in practice, we have more DOF than we often want with any digital camera, because the lens focal lengths are so small. for instance, the lens on a swivel coolpix is about 6mm to 20 or 24 mm. and yes, those are the same mm you would use if you were thinking about DOF in a 35mm SLR camera. and from that, we know that a 24mm lens has a great DOF. the fact that the digital sensor is tiny, making the "normal" SLR lens of 50mm equate to about a 12mm digicam lens, is something we have to live with. so unless you zoom in all the way, you'll probably find your DOF experiments are frustrating - at least if you are doing portrait work. if you're a landscape photog, you'll love the increased DOF you get.

that's one reason that the fairly small minimum aperature of a digicam isn't an issue that you might think if you're coming from the 35mm world. f11 is plenty small enough for huge DOF with a 12mm lens.

the one place it's still an issue is with macro work. make the camera to subject distance small enough, and you have no DOF. it would be that much worse with a 35mm camera, so in this we're lucky. but you will still have tiny DOF 1" from the lens in a macro shot. but you can still use the formula to make it best you can. smaller lens, so zoom OUT 'till the flower is just ready to not be yellow, use small aperature. that's as much as you can do.

there is a calculator at this link that you can play with to see what DOF is with different combinations of settings.
http://www.shuttercity.com/DOF.cfm
good luck with it.
greg

Sorry for the basic questions but just trying to understand the dof
thing a little better

When I set the Nikon 5700 into Aperture priority mode are the
following assumptions correct?

1) If I use a larger F stop then my pictures will have more depth
of field?

2) Assuming I set the F stop higher and therefore, less light comes
into the camera and you have more dof: Will the Nikon be trying to
lower the Shutter speed to allow more light in?

3) I get confused with point 2 as the camera seems to lower shutter
speed to let more light in wont that affect the dof and the
brightness of the pic.

Any comments welcome...

thanks
Mark..

--
Greg Matthews

 

[Ching-Kuang Shene]

When I set the Nikon 5700 into Aperture priority mode are the
following assumptions correct?

1) If I use a larger F stop then my pictures will have more depth
of field?

2) Assuming I set the F stop higher and therefore, less light comes
into the camera and you have more dof: Will the Nikon be trying to
lower the Shutter speed to allow more light in?

3) I get confused with point 2 as the camera seems to lower shutter
speed to let more light in wont that affect the dof and the
brightness of the pic.

My Depth of Field page provides you with the most basics. Check my 4500 user guide. Don't worry about the camera model because the concept is not camera specific.

CK
http://www.cs.mtu.edu/~shene/DigiCam
950/990/995/2500/4500 user guide

 

[Neo Fight]

Although, in general, if the whole
photo is underexposed 1 to 2 stops, it may be more advisable to
increase ISO as exposure compensation can muddy your colors as well
as add noise.

Hi Karen.

Can you please explain? Thanks.

 

[kecohen]

Although, in general, if the whole
photo is underexposed 1 to 2 stops, it may be more advisable to
increase ISO as exposure compensation can muddy your colors as well
as add noise.

Hi Karen.

Can you please explain? Thanks.

I'll try. When you use exposure compensation, you are trying to correct for a predominance of light or dark that would effect the exposure of the subject. For example, suppose you are photographing a bride--white dress. If you focus on the bride, the camera's meter wants to make that dress 18% (or what we call "middle" gray.) So, to get the dress white, we can tell the camera to compensate up a stop or more. Of course, as far as the camera's concerned, you are overexposing the photo. You will lose the details in any areas that were llighter than the dress. You will also add some noise into the dark areas.

But say you're shooting a moving target indoors in low contrast light and you can't use a flash. You have to have a fast shutter, but you're already at max aperture. You know that your whole photo would be 1 to 2 stops underexposed. By increasing the CCD sensitivity, or film sensitivity, you are increasing the speed at which the image is imprinted, without affecting the exposure value--the camera will adjust to give you a proper exposure--neither over nor underexposed, and at the cost of just a little noise.

On the other hand, a uniformly underexposed image has a lack of contrast to begin with. If you try to EV compensate up, and you are already at or near the limits of what your camera can give you--you still end up with a dark image, lousy contrast & muddy colors. But you'll also get noise in the dark areas.

--
Karen

...but if you try sometimes, you just might find, you get what you need.
Minolta 7000i, accessories and lenses, lenses, lenses; CP5700, TC15ED,
Kenko KUT-300 Hi, SB80X Speedlight, Epson Stylus 980N, Epson 7600
(shared), Epson Expression 1680 w/ transparency unit, Tamron Fotovix
60WU....
http://www.e-designarts.com
http://www.pbase.com/kecohen/