Depth of Field Question
Feb 24, 2014 09:29:07 #
sirlensalot
Loc: Arizona
[quote=Terra Australis]Actually you are losing sight of the answer. The lens may well be set to f5.6 but once you put the 1.4TC the focal length of the lens increases. So the aperture goes from f5.6 to about f9, regardless of what it says so on the lens.
To argue that a TC does not cut down the amount of light passing through the lens would put you on shaky ground.[/
Will agree with you on this one.
To argue that a TC does not cut down the amount of light passing through the lens would put you on shaky ground.[/
Will agree with you on this one.
Feb 24, 2014 09:37:50 #
Keep in mind a TC magnifies the image thrown by the lens. As such, it does not actually physically change the focal length or size of the aperture but does change the "aparent" focal length by spreading the cone of light and the "aparent" f-stop by reducing the intensity of light at the sensor. The actual DOF remains the same - but also is magnified - so our perception of it makes it appear less ......That's my story and I'm sticking to it !
Feb 24, 2014 09:45:25 #
imagemeister wrote:
Keep in mind a TC magnifies the image thrown by the lens. As such, it does not actually physically change the focal length or size of the aperture but does change the "aparent" focal length by spreading the cone of light and the "aparent" f-stop by reducing the intensity of light at the sensor. The actual DOF remains the same - but also is magnified - so our perception of it makes it appear less ......That's my story and I'm sticking to it !
As has been mentioned, the whole concept of DOF is a very nebulus subject and any attempt to pin numbers on it is difficult at best. - So, do not put much faith in any DOF "calculator" or table - they are just very rough guides ....
Feb 24, 2014 09:57:14 #
Feb 24, 2014 10:40:03 #
Dds82 wrote:
So what is the true accurate answer to that interesting but difficult question? Lol
As Bob Dylan once said "The answer is blowin in the wind " .....
Feb 24, 2014 11:10:08 #
To add a practical application to this discussion. I was trying to get a much larger DOF to a project and am now looking at point and shoot style cameras that come with a smaller sensor to achieve that end.
Feb 24, 2014 11:21:45 #
mcveed wrote:
Here's one for the DOF experts. If I take a picture of a bird 30 feet away with a 300mm lens at f5.6 my Depth of Field will be 12 inches deep. Now, if I put a 1.4 teleconverter on the lens, which makes it effectively a 420mm lens, will my Depth of Field remain 12 inches deep, or will it change?
Of course it changes, just as your aperture changed, your /f5.6 turned into an /f8, as did the focal length.
Feb 24, 2014 11:34:02 #
zerobeat wrote:
To add a practical application to this discussion. I was trying to get a much larger DOF to a project and am now looking at point and shoot style cameras that come with a smaller sensor to achieve that end.
It is not the sensor size directly that causes this phenomenon - it is the smaller relative aperture sizes of the shorter focal length lenses used by the smaller sensor that is the direct cause of this ....
Feb 24, 2014 11:38:01 #
imagemeister wrote:
Keep in mind a TC magnifies the image thrown by the lens. As such, it does not actually physically change the focal length or size of the aperture but does change the "aparent" focal length by spreading the cone of light and the "aparent" f-stop by reducing the intensity of light at the sensor. The actual DOF remains the same - but also is magnified - so our perception of it makes it appear less ......That's my story and I'm sticking to it !
The whole notion of DOF is based on human perceptions - which can vary greatly !
Feb 24, 2014 11:57:59 #
Racmanaz
Loc: Sunny Tucson!
Who cares? just shoot it both ways and see what you like and this will end this endless argument lol ;)
Feb 24, 2014 11:58:46 #
It always amazes me when shooting the moon with 420mm of focal length, that getting the exact focus is such a touchy issue.
One could assume that the distance to the moon is very close to the infinity mark for your long lens, but still it takes a very gentle and steady touch of your hand to manually set a good focus. It's like the DOF is paper thin.
On the other hand, getting a good focus on the moon using low power lens is very easy, ie, large DOF.
One could assume that the distance to the moon is very close to the infinity mark for your long lens, but still it takes a very gentle and steady touch of your hand to manually set a good focus. It's like the DOF is paper thin.
On the other hand, getting a good focus on the moon using low power lens is very easy, ie, large DOF.
Feb 24, 2014 12:23:09 #
Kingmapix wrote:
It always amazes me when shooting the moon with 420mm of focal length, that getting the exact focus is such a touchy issue.
One could assume that the distance to the moon is very close to the infinity mark for your long lens, but still it takes a very gentle and steady touch of your hand to manually set a good focus. It's like the DOF is paper thin.
On the other hand, getting a good focus on the moon using low power lens is very easy, ie, large DOF.
One could assume that the distance to the moon is very close to the infinity mark for your long lens, but still it takes a very gentle and steady touch of your hand to manually set a good focus. It's like the DOF is paper thin.
On the other hand, getting a good focus on the moon using low power lens is very easy, ie, large DOF.
Not really. The moon is about 240000 miles, that is with in the DoF of a 420mm lens & probably a 4200mm lens. You can play around with DoF calculators to check that out. The problem you have is probably because many long lenses will focus past infinity. This may be because it is not possible to set the stop accurately at infinity and temperature changes can change the length of the lens barrel enough to make it impossible to use a factory set infinity mark.
dsturgis
Feb 24, 2014 12:27:03 #
I go with the link to Stack Exchange.
At a given distance from the camera the DoF depends on the Circle of Confusion used to calculate the DoF and the actual lens opening. Focal length and f stop do not enter in except to determine the actual lens opening.
At a given distance from the camera the DoF depends on the Circle of Confusion used to calculate the DoF and the actual lens opening. Focal length and f stop do not enter in except to determine the actual lens opening.
Feb 24, 2014 12:45:07 #
Racmanaz wrote:
Who cares? just shoot it both ways and see what you like and this will end this endless argument lol ;)
I do, for one. Seems like others are also interested. It baffles me why you would make such a comment. If your not interested, move on to another topic that you may have interest to you.
Feb 24, 2014 13:07:47 #
Dean Sturgis wrote:
I go with the link to Stack Exchange.
At a given distance from the camera the DoF depends on the Circle of Confusion used to calculate the DoF and the actual lens opening. Focal length and f stop do not enter in except to determine the actual lens opening.
At a given distance from the camera the DoF depends on the Circle of Confusion used to calculate the DoF and the actual lens opening. Focal length and f stop do not enter in except to determine the actual lens opening.
The size of the circle of confusion is where the controversy of human perception comes in .....
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