Andmmy wrote:.

Is there a difference between the DOF of f2.8 from a DSLR vs f2.8from a compact camera such as a Canon A710 that has aperture control?.

Yes, a huge difference..

Will I still get the nice shallow DOF with a compact or does the lensfrom a DSLR really make a difference?.

No, you won't be able to get shallow depth of field with a compact. It's not the lens, it's the tiny sensor. The bigger the sensor (or film), the more shallow the depth of field at a given aperture and composition...

The shorter the real focal length (that means ignore the figures for "35 mm film equivalent" and use the real ones) the less DoF you have. So smaller compacts have smaller focal lengths etc etc..

Regards, David..

Sorry I was thinking one thing and typing another. Short focal lengths mean lots of DoF..

I'll go an lie down quietly and take a tablet. .

Regards, David..

The equation for depth of field is:.

DOF=2(circle_of_confusion)(f-stop)(subject_size)^2/(sensor_size)^2.

Circle_of_confusion is pretty much constant so the DOF for a particular subject filling the sensor field, a flower for example, increases strongly as the sensor size decreases...

Andmmy wrote:.

Is there a difference between the DOF of f2.8 from a DSLR vs f2.8from a compact camera such as a Canon A710 that has aperture control?.

For a given angle of view, the f/2.8 lens on a DSLR will give less depth of field simply because to provide that angle of view the DSLR lens need be longer. To achieve roughly the same wide angle of view as the A710's lens in it's widest position (5.8mm focal length), an Olympus DSLR must have a 17.5mm lens mounted on it, which is more than 3 times longer. On a Sigma DSLR, you would need a ~20-21mm lens. On a Nikon, Pentax or Sony DSLR you would need a ~23-24mm one. On a full-frame body, you would have to mount a 35mm lens. Assuming all lenses are set to f/2.8 and the camera-to-subject distance is constant, the 35mm lens will provide the least depth of field, as it's focal length is more than 6 times greater than that of the A710's at it's widest position. (Depth of field decreases with focal length assuming the aperture and camera-to-subject distance stays the same.)..

RE>Will I still get the nice shallow DOF with a compact <.

Those of us who like sharp pictures think the smaller sensor with greater depth of field is a benefit, not a negative..

Especially valuable for closeups where D-SLR depth of field is terrible..

BAK..

BAK wrote:.

Those of us who like sharp pictures think the smaller sensor withgreater depth of field is a benefit, not a negative..

Especially valuable for closeups where D-SLR depth of field is terrible..

BAK.

You easily obtain greater DOF with a DSLR in a closeup by stopping down your aperture...

Andmmy wrote:.

Is there a difference between the DOF of f2.8 from a DSLR vs f2.8from a compact camera such as a Canon A710 that has aperture control?.

Yes..

The A710's 1/2.5" sensor will work against you along with the maximum aperture of 4.8 at the tele end..

Below are some sample shots taken with my Pano FZ20 which has the same size sensor, but which has a constant 2.8 aperture throughout the zoom range..

Background fairly far beyond subject so helps with blurf2.8 @ 63mm (35mm equiv. = 378mm).

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Camera-to-subject distance fairly short which can helpf3.7 @ 72mm (35mm equiv. = 432mm).

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Why I took this at f5.6 is beyond me - wasn't thinking.

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Crop from same image.

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Macro Mode (or could simply be a close-up shot taken in one of the other modes - don't remember) - intentionally trying to get the dof as shallow as possiblef2.8 @ 7mm (35mm equiv. = 42mm).

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F2.8 @ 12mm (35mm equiv. = 72mm).

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Transformer a good 30-40 ft away if memory servesf8 @ 72mm (35mm equiv. = 432mm).

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F8 @ 72mm (35mm equiv. = 432mm).

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F8 @ 49mm (35mm equiv. = 294mm).

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Good Day,Roonal.

'Money doesn't buy happiness, but it makes for an extravagant depression' by golf tournament sportscaster..

The circle of confusion is proportional to sensor size so small sensors have significantly smaller CoCs compared to DLSR sensors..

Dave Martin wrote:.

The equation for depth of field is:.

DOF=2(circle_of_confusion)(f-stop)(subject_size)^2/(sensor_size)^2.

Circle_of_confusion is pretty much constant so the DOF for aparticular subject filling the sensor field, a flower for example,increases strongly as the sensor size decreases..

Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..

I guess that means if I want to be able to take nice portraits that really isolate the subject and blur the background then a dslr is the way to go. Am I right?.

Andmmy..

Andmmy wrote:.

I guess that means if I want to be able to take nice portraits thatreally isolate the subject and blur the background then a dslr is theway to go. Am I right?.

With a DSLR and a fast (ie. large aperture) lens, blurring the background and/or foreground can be done over a greater variety of camera-to-subject & subject-to-background distances versus with using P&S..

Good Day,Roonal.

'Money doesn't buy happiness, but it makes for an extravagant depression' by golf tournament sportscaster..

Andmmy wrote:.

I guess that means if I want to be able to take nice portraits thatreally isolate the subject and blur the background then a dslr is theway to go. Am I right?.

Either that or do it the way that professional photographers did it for over a century: use a backdrop...

Doug Pardee wrote:.

Andmmy wrote:.

I guess that means if I want to be able to take nice portraits thatreally isolate the subject and blur the background then a dslr is theway to go. Am I right?.

Either that or do it the way that professional photographers did itfor over a century: use a backdrop..

Or if outdoors make sure the background is very far away (hundreds of yards)...

Leon,.

I've not heard of a relationship between sensor size and CoC. I'd appreciate a reference so I can learn about it..

I've argued (and have read) that the lower limit of COC is the diffraction limit or the distance between pixels (whichever is larger), but most cameras & display systems don't reach that level of performance..

Dave..

Andmmy wrote:.

I guess that means if I want to be able to take nice portraits thatreally isolate the subject and blur the background then a dslr is theway to go. Am I right?.

Yes. That's right..

But shallow DoF isn't the ONLY way to do get an isolating background... .

In the portrait studio, seamless paper backgrounds also canvasses with "pre-blurred" effects painted on them can be used with any size of camera....

...and they can be used at ANY convenient aperture not just the wide ones.. Regards,Baz..

Dave Martin wrote:.

Leon,I've not heard of a relationship between sensor size and CoC. I'dappreciate a reference so I can learn about it..

Generally, the CoC relates to the eye's acuity when looking at about an 8x10 print at about a foot. That translates to about about 1/100th of an inch. Demagnify 1/100th of an inch on the 8x10 print to the sensor dimension and you have the CoC. That is approximately how it is figured. Sometimes it is expressed as a fraction of the diagonal..

I've argued (and have read) that the lower limit of COC is thediffraction limit or the distance between pixels (whichever islarger), but most cameras & display systems don't reach that level ofperformance..

Diffraction is another source of blur in an image that trades off against DoF throught the f number. Focus blur at a some distance from the focus point decreases as f number increases but diffraction blur increases. Obviously, the pixel spacing became relevant with the advent of digital sensors. There are some good numbers to know regarding your particular camera. I use a 1.3 crop camera with 8.3 MP and that gives an approximate 8 micron (0.008mm) pixel spacing..

Diffraction in an image with high contrast detail using my normal processing is negligeable at f/11 or small f number. It becomes apparent at f/14 and is typically significant at f/16 and larger f numbers. Obviously, with lesser detail in an image, diffraction is less apparent at any given f number. (Interestingly, my sensor resolves about 56 lp/mm at a MTF of about 0.5. Diffraction at f/14 limits resolution to about the same 56 lp/mm at a MTF of about 0.5 showing consistancy with the above emperical observations of where diffraction blur is apparent.).

Thus for me, DoF is free up to about f/11 to f/14. Above that, diffraction begins to increase as DoF increases. If I look at a fixed DoF, there will be an f number where the total focus plus diffraction blur will be relatively uniform across the DoF. That is the so called "optimim" f number. For my camera the optimum f number is about 4.9 * sqrt (f number) where f number provides the original fixed DoF..

While figuring this all out can take some time and study, it can be worth it depending on what you shoot..

Dave.

Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..