DOF on "Super-Zooms"

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windwalkerone

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The one problem I have with the “Ultra-Zoom” cameras is their DOF. I have a Sony A300 DSLR with a Tamron 18-200mm lens on it. Last week I playing around with a Canon SX10 is. I was quite impressed with the Canon until I tried the macro on some flowers. I have a patch of Daisies that I used for both cameras. The Sony with the 18-200 Shot at 200mm, f3.5 1/250 gave me nice close-up of the Daisy and a nice blurry background. The same shot with the Canon SX10 and the zoom lens at 200mm, f3.5 1/250 gave me a greater DOF, meaning I got a good close-up of Daisy, but the background looked as if was just out of focus. I couldn’t get rid of any background. When I work with macro shooting, most of the time I like to isolate the subject. Are all “Super-Zooms” like that with their Macro? It's too bad if thats the case, because that Canon Powershot SX10 IS was a great camera for back-packing
 
heidfirst said:
http://photo.net/learn/optics/dofdigital/
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The link refers to crop format DSLRs compared to full frame, whereas the OP is comparing a crop format DSLR with a compact.

The effect is the same, but much more pronounced with the compact. Basically, the tiny sensor size of compact cameras (including bridge/hybrid and SLR-lookalikes) endows them with vast depth of field. You almost don't need to focus them. This makes life easier for sharp snaps, but robs creative users of a primary photographic technique.

Relative to full frame digital, crop format DSLRs have a crop factor of around 1.5x. By the same measure, compacts have a crop factor of about 5x or 6x.

Actual DoF calculations are here www.dofmaster.com
 
HoppyUK said:
The link refers to crop format DSLRs compared to full frame, whereas the OP is comparing a crop format DSLR with a compact.

The effect is the same, but much more pronounced with the compact. Basically, the tiny sensor size of compact cameras (including bridge/hybrid and SLR-lookalikes) endows them with vast depth of field. You almost don't need to focus them. This makes life easier for sharp snaps, but robs creative users of a primary photographic technique.

Relative to full frame digital, crop format DSLRs have a crop factor of around 1.5x. By the same measure, compacts have a crop factor of about 5x or 6x.

Actual DoF calculations are here www.dofmaster.com
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If I have told you once, I have told you a thousand times the huge DOF comes from the tiny FL of the lens. All these calculations originate from the hyperfocal distance. ( FL^2/(aperture * C of C)/1000. Note the FL in the calculation. No mention of the sensor.
 
classcams said:
If I have told you once, I have told you a thousand times the huge DOF comes from the tiny FL of the lens. All these calculations originate from the hyperfocal distance. ( FL^2/(aperture * C of C)/1000. Note the FL in the calculation. No mention of the sensor.
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Though it does mention 'C of C' ;)
 
classcams said:
If I have told you once, I have told you a thousand times the huge DOF comes from the tiny FL of the lens. All these calculations originate from the hyperfocal distance. ( FL^2/(aperture * C of C)/1000. Note the FL in the calculation. No mention of the sensor.
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I don't think you've managed a 1000 times with 178 posts so far? - or have I missed something :)

C or C is affected by sensor size, so thats where the sensor comes into it - eg a D300 (cropped) has a C of C of .020 whereas a D700(full frame) has a C of C of 0.030. The OP states thats the focal length of both shots in the original was 200mm so not sure how thats tiny. Just for information mot compacts have a C of C of around 0.005 so thats where the increased DoF comes from then

Hugh
 
Excuse my ignorance, but what is C of C? :thinking:
 
Thanks all. I'm humbled by my ignorance.
 
Just looked at the link kindly supplied to explain. I have a headache, and will try again later!
 
boyfalldown said:
C or C is affected by sensor size, so thats where the sensor comes into it - eg a D300 (cropped) has a C of C of .020 whereas a D700(full frame) has a C of C of 0.030. ... Just for information mot compacts have a C of C of around 0.005 so thats where the increased DoF comes from then
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Yes, but ...

From the Wikipedia article we've all referenced:
In photography, the circle of confusion diameter limit (“CoC”) is sometimes defined as the largest blur circle that will still be perceived by the human eye as a point when viewed at a distance of 25 cm (and variations thereon).
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Let's see if we can follow that through. Suppose your lens focuses a cone of light into a disc which is 0.01mm across. On a DSLR that's smaller than the CoC limit so it will show as a point on the print, whereas with a compact camera it's larger than the CoC limit so will be seen as an out-of-focus disc. (Another way of looking at it is that, other things being equal, the greater magnification required from the small sensor on a compact camera means that in-focus points are magnified to out-of-focus discs.

But wait! Surely that's saying that compact cameras produce less Depth Of Field?

The issue is with those weasel words "other things being equal". They aren't. A compact camera uses a much smaller focal length than a DSLR to compose the same shot, and as we all know (don't we?), other things being equal, a smaller focal length gives you greater DOF.

It is possible to combine the CoC and the focal length in one formula - see the Wikipedia article on DOF. If you can get your head round the maths, it indicates that the focal length effect usually dominates the CoC effect. Which is why compact cameras give you greater DOF.

So I think what I'm saying is that classcams is basically right.
 
now my head hurts :)

I see what you mean, and although I think you're pretty much right having worked through a couple of examples I think the statement 'No mention of the sensor' is wrong. If you look at the differences between Full Frame and Crop Sensors, where the DoF is often mentioned, then that clearly shows the sensor size does have a noticeable impact

Hugh
 
:D

Getting back to the question...

Looking at the specs of the Powershot SX10 IS, it seems that the actual focal length range is 5-100mm giving an effective range of 28-560mm on a sensor 6.16 x 4.62 mm or 0.28 cm². That would suggest when set to 200mm the real focal length is actually just 36mm.
 
^^exactly that^^

At the end of the day, the actual mechanics of it dont really matter. You cant get great DoF on a compact. You can however, take it backpacking and still get some amazing photos. You just have to shoot within the limitations of the equipment, same a you do with any camera.
 
Gandhi said:
^^exactly that^^

At the end of the day, the actual mechanics of it dont really matter. You cant get great DoF on a compact. You can however, take it backpacking and still get some amazing photos. You just have to shoot within the limitations of the equipment, same a you do with any camera.
Click to expand...

What's a single letter between friends - apart from reversing the whole meaning :shrug:
 
classcams said:
If I have told you once, I have told you a thousand times the huge DOF comes from the tiny FL of the lens. All these calculations originate from the hyperfocal distance. ( FL^2/(aperture * C of C)/1000. Note the FL in the calculation. No mention of the sensor.
Click to expand...

LOL, I don't quite remember a thousand times, but your repeated reference to the lens alone in these matters is only an effect, not the primary cause.

The sensor size is fundamental in a camera. Everything hinges around it. The only reason you have very short focal lengths on compacts is because of the small format.

The sensor size is referenced in your formula by the CoC.

Edit: which basically means, you agree with me. Or if you prefer, I agree with you :)
 
The more I read this thread, the bigger my CoC gets :shrug::lol::lol::lol:
 
HoppyUK said:
LOL, I don't quite remember a thousand times, but your repeated reference to the lens alone in these matters is only an effect, not the primary cause.

The sensor size is fundamental in a camera. Everything hinges around it. The only reason you have very short focal lengths on compacts is because of the small format.

The sensor size is referenced in your formula by the CoC.

Edit: which basically means, you agree with me. Or if you prefer, I agree with you :)
Click to expand...
It is the old chicken and egg situation. focal length, angle of view, size of sensor
 
classcams said:
It is the old chicken and egg situation. focal length, angle of view, size of sensor
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Can we call this one an honourable draw?

You're right when you say that it's the smaller focal lengths, rather than the sensor size per se, which have the biggest effect on DOF.

But HoppyUK is right when he says that the sensor size is the fundamental variable and that everything follows from that.
 
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