F2.8 = shallow DOF and its a wide angle lens??


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richliow

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Jul 9, 2005
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Hi Folks,

Beening reading up a lot on photography lately.
Read that the bigger the aperture number, the smaller the DOF.
Which means more blurring in the foreground and background.

And I read that wide angle lens are used for taking buildings...

Then I saw this Wide Angle Lens with F/2.8
Nikon AF 14mm f/2.8D ED

My confusion here.... if its WIde Angle lens, it should be able to take
pictures very vividly ie... foreground as well as background in sharp focus...
but hey, this is F/2.8 so wouldnt there be a contradiction....?

I know i probably am missing some point in the above....
so i am seeking help from gurus here to help me nail my confusion...

cheers
 

Jan 23, 2005
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#3
richliow said:
Read that the bigger the aperture number, the smaller the DOF.
...
My confusion here.... if its WIde Angle lens, it should be able to take
pictures very vividly ie... foreground as well as background in sharp focus...
but hey, this is F/2.8 so wouldnt there be a contradiction....?
A larger aperture will result in less depth of field (IF you compare similar focal lengths). A shorter focal length will result in more depth of field (IF you compare similar apertures).

If you compare different focal lengths and different apertures at the same time, you may end up with to two trends that either reinforce or attenuate each other. So there is no contradiction.
 

catchlights

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#4
richliow said:
Hi Folks,

Beening reading up a lot on photography lately.
Read that the bigger the aperture number, the smaller the DOF.
Which means more blurring in the foreground and background.

And I read that wide angle lens are used for taking buildings...

Then I saw this Wide Angle Lens with F/2.8
Nikon AF 14mm f/2.8D ED

...................................

cheers
Bigger the aperture number, smaller the "hole", grater the depth of field.

Nikon AF 14mm f/2.8D ED, means the maximum aperture (the hole) for this lens is f2.8, not asking you to shoot at f2.8.
 

richliow

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#5
catchlights said:
Bigger the aperture number, smaller the "hole", grater the depth of field.

Nikon AF 14mm f/2.8D ED, means the maximum aperture (the hole) for this lens is f2.8, not asking you to shoot at f2.8.

I know where i am confused now....
from what you have said, the maximum aperture of this lens is f2.8.....
so that meaning,
i can decrease the aperture.....and get a wide angle picture with ermmm lets say sharp focus at the back and foregrounds right?
:)
 

richliow

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Jul 9, 2005
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#6
oh one more thing...
14 mm .....does this mean that I cant zoom the lens?
 

catchlights

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#7
richliow said:
oh one more thing...
14 mm .....does this mean that I cant zoom the lens?
Right, you can’t zoom this lens as this is a fixed focal length (14mm) lens.

richliow said:
I know where i am confused now....
from what you have said, the maximum aperture of this lens is f2.8.....
so that meaning,
i can decrease the aperture.....and get a wide angle picture with ermmm lets say sharp focus at the back and foregrounds right?
:)
Yes, you can use from f2.8 till f22, please read from the web regarding the relationship between depth of field and aperture, I’m not good in technical writing to explain in details.
 

tmh

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Oct 8, 2005
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Depth of Field (DOF) depends on a few factors such as aperture size, focal length, subject distance, sensor (medium) size etc. In practice, a wide angle lens such as 14mm (used at F2.8 for example) would have a greater DOF compared to a telephoto lens such as 200mm (used at F2.8), if the other factors are same.
 

Andy Ho

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#11
In case you don't know...

In actual fact if you are shooting with a tripod using the 14mm lens you don't really need to be shooting at f/2.8 as you can close down your aperture for maximum depth of field.

The fact that there is an f/2.8 aperture on the lens was intended for people who need to shoot in low light and does not have a tripod handy. The bigger aperture at f/2.8 allows a photographer to handhold his camera and shoot at a higher shutter speed.

Remember that shutter speed and aperture works in a reciprocal relationship.
 

surfer18

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#13
Andy Ho said:
In case you don't know...

In actual fact if you are shooting with a tripod using the 14mm lens you don't really need to be shooting at f/2.8 as you can close down your aperture for maximum depth of field.

The fact that there is an f/2.8 aperture on the lens was intended for people who need to shoot in low light and does not have a tripod handy. The bigger aperture at f/2.8 allows a photographer to handhold his camera and shoot at a higher shutter speed.

Remember that shutter speed and aperture works in a reciprocal relationship.
Fully agreed with the above. The large Aperature for Wide Angle is for low light conditions or moving things. If for static photography, 99% on tripod & cable release. The F/22 is not usually use. Usually use is wide angle between F/8~F/11.
 

litefoot

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Jan 27, 2005
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#14
tmh said:
Depth of Field (DOF) depends on a few factors such as aperture size, focal length, subject distance, sensor (medium) size etc. In practice, a wide angle lens such as 14mm (used at F2.8 for example) would have a greater DOF compared to a telephoto lens such as 200mm (used at F2.8), if the other factors are same.
Sensor size will not affect DOF.
 

singscott

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#15
litefoot said:
Sensor size will not affect DOF.
I used to say that. But I was wrong, sensor size and film size it does affect DOF. There this thing call COC or circle of confusion. Meaning mainly there different lens designs for different film or sensor formats thus different lens deisign cause the DOF to change. For example a small format 90mm will have more DOF then a large format 90mm althought in large format 90mm is a wide angle and the small 90mm is a tele lens.That because a small format 90mm is design with a small image circle and a large format 90mm it is deisgn with a huge image circle.;)
 

richliow

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Man, what you just type.... created this thing call COC in me....
confused ....liao... =P
 

Andy Ho

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#17
This is extracted from DOF Masters

"Since circles of confusion are formed by light rays passing through the lens tube, the size of a circle of confusion is proportional to the amount of light that can pass through the lens tube. This means smaller (resp., larger) circles of confusion will be formed if less (resp., more) light can pass through. Restricting how much light can pass through the lens is the function of the diaphragm in the lens tube that sets the aperture values. Therefore, a smaller aperture means a smaller diaphragm opening, which, in turn, means allowing less light to strike the film/CCD plane. Thus, we have smaller circles of confusion and, as a result, a sharper image"

In another words, the bigger the aperture the more circle of confusion and thus a lens with a big tube (lens body) also equals more circle of confusion. That said, a medium format lens will produce more blur than a DSLR. A DSLR will produce more blur than a prosumer digital camera.

How much DOF you get also partially has to do with the format of the camera. The bigger the sensor size the lesser DOF you get. A smaller sensor lacks the resolving power of a bigger sensor and thus renders things a little more sharper. Ever consider why it is so difficult getting a blur background on a prosumer digital camera?
 

litefoot

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#18
singscott said:
I used to say that. But I was wrong, sensor size and film size it does affect DOF. There this thing call COC or circle of confusion. Meaning mainly there different lens designs for different film or sensor formats thus different lens deisign cause the DOF to change. For example a small format 90mm will have more DOF then a large format 90mm althought in large format 90mm is a wide angle and the small 90mm is a tele lens.That because a small format 90mm is design with a small image circle and a large format 90mm it is deisgn with a huge image circle.;)
CoLC? That's medium/sensor type, the ability to register smaller CoLC which gives more DOF. If you are speaking of the size of the plane, no.
 

singscott

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#19
litefoot said:
CoLC? That's medium/sensor type, the ability to register smaller CoLC which gives more DOF. If you are speaking of the size of the plane, no.
No. I mean the design of the lens for the different format or size of the digital sensors or films. Basicly image circle. Different sensors or film formats have different image circle from their lens. So you can say size of sensor does count here because of the lens design to go with it. I not really the expect here. But you can get more information if you do a search for "photography DOF COC" you will get tons of information. Here one http://www.wrotniak.net/photo/dof/ ;)
 

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