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DOF Question
I apologise if this is a dumb question - however I will ask anyway - Is the DOF relatively the same on different lenses - if they are set on the same settings?.

For example:.

If my Canon 50mm prime 1.8 lens is set at 5.6 will the DOF be the same as my sigma (70-200mm) set at 50mm 5.6?.

Is there such a thing as a DOF table - where you inter the F stop, distance etc and it shows you the size of the DOF?.

Kind regards,Mil...

Comments (6)

Milbogo wrote:.

I apologise if this is a dumb question - however I will ask anyway -Is the DOF relatively the same on different lenses - if they are seton the same settings?.

No question is dumb, it's just one you don't know the answer to..

DOF is determined by 3 factors; focal length, aperture and distance from the subject..

For example:If my Canon 50mm prime 1.8 lens is set at 5.6 will the DOF be thesame as my sigma (70-200mm) set at 50mm 5.6?.

Yes, assuming what is marked as 50mm is the same actual focal length - any variation will be due to the difficulty in ascertaining exactly where the same focal length occurs, lenses tend to vary a little and focus distance on a zoom will vary focal length in a different manner than a prime at the same focal length..

I don't understand lens geometry well enough to give more details, but in theory, 50mm with the same aperture, subject distance on the same camera should give the same DOF. It's not quite that simple (DOF relies on some subjective judgments as to perceived acceptability of sharpness, which relates to final viewing distance etc.), but for most practical purposes it is..

Is there such a thing as a DOF table - where you inter the F stop,distance etc and it shows you the size of the DOF?.

There is indeed, see: http://www.dofmaster.com/dofjs.html.

I've written a tutorial on DOF, see: http://www.zenadsl5251.zen.co.uk/photos/doftut.html.

So many photos, so little time.http://www.peekaboo.me.uk - general portfolio & tutorialshttp://www.boo-photos.co.uk - live music portfoliohttp://imageevent.com/boophotos/ - most recent images.

Please do not amend and re-post my images unless specifically requested or given permission to do so...

Comment #1

Milbogo wrote:.

Is there such a thing as a DOF table - where you inter the F stop,distance etc and it shows you the size of the DOF?.

I prefer it in this format:.

Http://www.dofmaster.com/doftable.html.

You can print it off for a few focal lengths and keep it with you in your camera bag.

-Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #2

Http://www.expodisc.com/...amp;productname=ExpoAperture2_Depth-of-Field_Guide(some of these converters take into account the size of the sensor as well).

Is there such a thing as a DOF table - where you inter the F stop,distance etc and it shows you the size of the DOF?..

Comment #3

Boo wrote:.

DOF is determined by 3 factors; focal length, aperture and distancefrom the subject..

Just to clarify, this is "for a given Circle of Confusion Diameter Limit". The CoCDL varies with different film/sensor sizes, and with personal tolerances for blurriness. For a given person with a given camera, it's usually pretty much constant..

Furthermore, except at close distances (say, within a half meter or couple of feet) the focal length and distance from subject can be combined into one variable: composition. DoF doesn't change significantly if you move in fairly close and use a shorter focal length or back way off and use a longer focal lengthfor a given composition it's pretty much the same..

For a given person with a given camera and a given subject composition, there is only one variable that significantly affects DoF: aperture...

Comment #4

Doug Pardee wrote:.

Just to clarify, this is "for a given Circle of Confusion DiameterLimit". The CoCDL varies with different film/sensor sizes, and withpersonal tolerances for blurriness. For a given person with a givencamera, it's usually pretty much constant..

I did already cover that, bearing in mind this is the 'Beginners Questions' forum and I used the subject caveat "for practical considerations", with:.

.. the same aperture, subject distance on the same camera shouldgive the same DOF. It's not quite that simple (DOF relies on somesubjective judgments as to perceived acceptability of sharpness,which relates to final viewing distance etc.), but for mostpractical purposes it is..

Furthermore, except at close distances (say, within a half meter orcouple of feet) the focal length and distance from subject can becombined into one variable: composition. DoF doesn't changesignificantly if you move in fairly close and use a shorter focallength or back way off and use a longer focal lengthfor a givencomposition it's pretty much the same..

For the same field of view/composition, yes, that's true. A 100mm lens from 20 feet away will give the same DOF as 50mm from 10' away-ish..

For a given person with a given camera and a given subjectcomposition, there is only one variable that significantly affectsDoF: aperture..

Indeed. But if you're struggling with insufficient DOF, changing composition (by decreasing focal length, or moving further back, or a little of both) as well as aperture can increase it. A modest change in each element, can increase DOF significantly without serious impact on the overall composition..

For example (using my 20D 1.6 crop factor DSLR for the numbers - it's the relative difference that's pertinent), if you're at 50mm @ f8 from 5 feet away, you would have around 10" DOF - a single step back to 7 feet away, widen to 40mm and stop down to f9 and you now have about 40" of DOF - so a modest tweak of all the elements together can effect a significant improvement - even remaining at f8, the change in composition alone will add 2' to the DOF. So where light may impact on aperture possibilities, DOF can be increased (or conversely decreased, if that's what's required) by adjusting composition/field of view..

So many photos, so little time.http://www.peekaboo.me.uk - general portfolio & tutorialshttp://www.boo-photos.co.uk - live music portfoliohttp://imageevent.com/boophotos/ - most recent images.

Please do not amend and re-post my images unless specifically requested or given permission to do so...

Comment #5

Milbogo wrote:.

I apologise if this is a dumb question - however I will ask anyway -Is the DOF relatively the same on different lenses - if they are seton the same settings?.

For example:If my Canon 50mm prime 1.8 lens is set at 5.6 will the DOF be thesame as my sigma (70-200mm) set at 50mm 5.6?.

Is there such a thing as a DOF table - where you inter the F stop,distance etc and it shows you the size of the DOF?.

Kind regards,Mil..

Set a 70-200 to 50mm. But any lenses set to the same focal lengths and apertures will have the same depth of field if it's measured by the same standards.Leonard Migliore..

Comment #6

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