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Old Dec 9, 2004, 8:30 PM   #1
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G'day! I'm looking for a camera that takes great shallow depth of field shots - portrait, food, product photography. I've currently got a Toshiba 3330 which has a canon lens with a minimum f-stop of F2.9. It takes great shallow depth of field shots, but only when you're quite close and is therefore not very good for blurred background portraits (for example). Should I look for a camera with a 'faster lens' or is there other features, attachments etc that would serve me better?

I'm currently considering the Canon G3 as it has a minimum f-stop of F2.0 and a relatively large pixel size on its CCD (I understand small pixel size is the major drawback between compacts and dSLRs).

I'd appreciate your opinions - cheers!
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Old Dec 11, 2004, 11:16 PM   #2
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It's not just f-stop that determines DOF, it is also the focal length of the lens too. In general, the higher the magnification, the less the DOF at any given f-stop. The wider the lens, the greater the DOF at any given f-stop. To give you an example, the older 35mm guys know that when using a lens such as a 24mm (a wide-angle lens), one can set the aperture at a point where focusing is not needed at all, because the dof is so wide.

As for pixel size being a drawback - it can be if the sensor size is too small, but this isn't always the case. I think that the major drawback between compacts and dslr's is more sensor size, rather than pixel size.

PhilR.


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Old Dec 12, 2004, 12:16 AM   #3
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Your actual G3 focal length is 7.2–28.8. That gives 35-140mm in 35mm equivalence. The reason is that the sensor is so much smaller than a 35mm negative. Since focal length is one of the determining factors in DOF you can see that you get a lot of DOF with prosumer digital cameras.

You will do better blurring the background with a f2.0 lens, but nowhere near what you can do with 35mm.

If you can get some increase in blur with distance you can enhance that in your image editor.

Generally the higher the pixel density the higher the noise. Some sensors are better than others and some cameras have more noise filtering than others. The G3 has a lower pixel density than the G5 & G6, so you should get less noise.


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Old Dec 12, 2004, 5:37 PM   #4
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slipe wrote:
Quote:
If you can get some increase in blur with distance you can enhance that in your image editor.
Thanks for the info guys.

Question the first:
When you say 'increase in blur with distance' does that mean the 'blurred background' effect is enhanced at the camera's full zoom range, ie I should try and get in a position where the subject is further away rather than closer? On my toshiba the manual focus jumps from 5m to 2m with nothing in between, which makes focusing kinda difficult and doesn't seem to do what I want anyway.

Question the second:
Given what you've said about focal length, is that more important in achieving the 'blurred background' effect than the minimum f-stop value? In terms of a compact digital, what combination of specs will give me the best opportunity for shallow DOF shots? If the answer is that even dSLR's struggle to get close to 35mm capability, should I maybe look for a dSLR instead? I'd appreciate your recommendations.

Question the third:
Are there any lens attachments from Tiffen etc which would enhance this effect?

Again, I appreciate your input.

Best regards

John G :-)
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Old Dec 12, 2004, 6:31 PM   #5
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As Slipe mentioned, the problem with a non-DSLR model is that the actual focal length of the lens is very short for any35mm equivalent focal length.

So, you'll have dramatically more depth of field for any given aperture, focus distance and 35mm equivalent focal length (since depth of field is based on the actual focal length).

See thispost for someone with a similar problem (you'll also see a link to a Depth of Field calculator):

http://www.stevesforums.com/forums/v...mp;forum_id=15


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Old Dec 12, 2004, 8:01 PM   #6
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OK. So I just discovered how much more dSLRs cost than compacts...:?

Given what we've discussed, which of these focal length and aperture combinations would be BEST to achieve the blurred background effect?

Canon pro1: 7.2-50.8, f2.4-3.5
Canon G3: 7.2-28.8, f2.0-3.0
Konica Z2: 6.3-63, f2.8-f3.7
Konica A2: 7.2-50.8, f2.8-3.5

Of these compacts, the Z2 has the highest AND lowest focal length value, but the G3 has the lowest f-stop value. What will make more difference, or does it depend on the sensor size? I've heard the 'mega zoom' models have very small sensors.

My current Toshiba has a focal length of 7.25-20.3 and f2.9-4.8.

Thanks again
jbng :-)
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Old Dec 12, 2004, 8:17 PM   #7
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I don't think you'll find any of the non-DSLR models to be acceptable for helping a larger subject stand out from backgrounds by blurring them (their depth of field is too great for blurring backgrounds significantly with larger subjects). You'd need to have too much space between your subject and the background for it to be practical in many conditions.

From a quick look at a DOF calculator, the Canon G Seriesat f/2.0 would have the shallowest depth of field (but, you'd also have some perspective distortion and barrel distortion at it's widest lens setting where f/2.0 is available).

Optical zoom won't really help you either (because you'd need to shoot from further away for your subject to occupy the same percentage of the frame, cancelling out anybenefit fromusing a longer focal length).

If you're on a budget, consider a model like the Canon Digital Rebel, and buy a 50mm f/1.8 lens to go with it (in addition to the kit lens).

Otherwise, I'd plan on using software to simulate a shallow depth of field for larger subjects like portraits with a non-DSLR model (unless you can put a lot of space between the subject and the background).

That's why I referred you to this thread:

http://www.stevesforums.com/forums/v...mp;forum_id=15



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Old Dec 13, 2004, 12:34 AM   #8
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Thanks guys, guess I'll continue deep etching whilst saving for a dSLR...

Appreciate your assistance.
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