Canon A80's Aperture

OrdiNance · 20th November 2003

Sorry guys, I'm kinda noob here and this question has probably been asked many times before.

I own a Canon A80 and i'm still not pretty clear on how to use the aperture function. I've heard that increasing the aperture size will result in bokeh. But are there other factors involved? Coz I can't seem to get the right effect.

sabre · 21st November 2003

Erm, I'll try to explain to the best of my ability. If you don't like reading theories, just note the underlined words. Please correct me if I'm wrong.

The Theory
For bokeh effect, you need very shallow Depth Of Field (DOF) such that the front and back of your subject will be out of focus. So the primary issue will be achieve a shallow DOF.

To achieve a Shallow DOF, from my knowledge it is dependent on 4 factors. First is the aperture size of the lens, second is the focal length used, third is the distance from the subject focused and forth is the circle of confusion of the lens.

Of the 4 factors we can normally only control the first 3. By using a large aperture size, meaning a low f-stop number, eg. f2.8 instead of f11 (bcoz f-stops are expressed in reciprocal), we will acheive a smaller DOF. Secondly, be increasing the focal length, eg. zooming to the telephoto end, we will also achieve a smaller DOF. Thirdly, by getting as close as possible to the subject focused, the DOF will be minimised. Lastly, for the circle of confusion, I think it is a property inherent to the lens itself and that is not something we can change unless we can change the camera's lens, so I shall keep this factor out of this discussion.

So in essence, to achieve maximum bokeh effect your lens can do, you put it to maximum zoom, largest aperture size, (eg. maximum telephoto zoom, at f2.8 for a80) and shoot your subject at a distance as close as possible.

One way you can achieve good bokeh with current consumer cameras is to shoot macro shots. This is achieved by using close up filters which makes your camera able to focus on the subject much closer than it original can. This works because our subject distance is very much reduced.

Now, one thing you have to realise that consumer digital cameras cannot achieve the level of bokeh effect that DSLR has. For consumer digital cameras, your Real focal length is very small, i.e. 7.8 (W) – 23.4 (T) mm for A80. Although on specifications, it states that the camera's 35mm film equivalent is 38 (W) – 114 (T) mm. This is not your real focal length. What it is saying is the magnification you achieve that is comparable to a 35mm film equilvalent camera.
I hope I didn't confuse you on this.

Take for example we assume that a good bokeh effect is acheivable at 80mm f2.8 on a SLR/DSLR. You will quickly realise that consumer cameras like a80 does not have a real focal length at 80mm! A80's maximum focal length is only 23.4mm. Therefore, the current consumer digital cameras will never match up to the bokeh ability of DSLRs unless they start making them with larger focal lengths which means requiring a larger CCD which means larger lens which means higher costs. You get the picture.

Conclusion
With all these concepts in mind, you will be able to change the DOF by altering any of the factors be it through your camera's inherent ability or through add-on accessories.

Phew, I think this is my longest post in Clubsnap. Hope that it helps.

OrdiNance · 21st November 2003

wow, thanks alot sabre. I'm grateful you took the time to explain it to me. I put what you've taught into practice. Hopefully one day i'll be able to post good bokeh shots.

I've taught about buying a dslr, the EOS 300D. But I'm still a beginner and i decided to take baby steps first. So I got the A80.

Well, thanks again!

theITguy · 21st November 2003

Thanks, learn something today too

sabre · 21st November 2003

Originally Posted by OrdiNance

wow, thanks alot sabre. I'm grateful you took the time to explain it to me. I put what you've taught into practice. Hopefully one day i'll be able to post good bokeh shots.

I've taught about buying a dslr, the EOS 300D. But I'm still a beginner and i decided to take baby steps first. So I got the A80.

Well, thanks again!

Hey no problem man. I'm glad that I'm of help.

BTW, I'm using s602z, and still got lots and lots to learn.

Probably till I can produce decent shots then I'll upgrade to a DSLR. But who knows when Canon will drop a DSLR onto the market at less than 1k!!!

johnyu · 22nd November 2003

sabre, well done!

20th November 2003	#1
OrdiNance New Member Join Date: Nov 2003 Location: CCK, Singapore Posts: 6	Canon A80's Aperture Sorry guys, I'm kinda noob here and this question has probably been asked many times before. I own a Canon A80 and i'm still not pretty clear on how to use the aperture function. I've heard that increasing the aperture size will result in bokeh. But are there other factors involved? Coz I can't seem to get the right effect.

21st November 2003	#2
sabre Member Join Date: Jun 2002 Location: Serangoon Posts: 97	Erm, I'll try to explain to the best of my ability. If you don't like reading theories, just note the underlined words. Please correct me if I'm wrong. The Theory For bokeh effect, you need very shallow Depth Of Field (DOF) such that the front and back of your subject will be out of focus. So the primary issue will be achieve a shallow DOF. To achieve a Shallow DOF, from my knowledge it is dependent on 4 factors. First is the aperture size of the lens, second is the focal length used, third is the distance from the subject focused and forth is the circle of confusion of the lens. Of the 4 factors we can normally only control the first 3. By using a large aperture size, meaning a low f-stop number, eg. f2.8 instead of f11 (bcoz f-stops are expressed in reciprocal), we will acheive a smaller DOF. Secondly, be increasing the focal length, eg. zooming to the telephoto end, we will also achieve a smaller DOF. Thirdly, by getting as close as possible to the subject focused, the DOF will be minimised. Lastly, for the circle of confusion, I think it is a property inherent to the lens itself and that is not something we can change unless we can change the camera's lens, so I shall keep this factor out of this discussion. So in essence, to achieve maximum bokeh effect your lens can do, you put it to maximum zoom, largest aperture size, (eg. maximum telephoto zoom, at f2.8 for a80) and shoot your subject at a distance as close as possible. One way you can achieve good bokeh with current consumer cameras is to shoot macro shots. This is achieved by using close up filters which makes your camera able to focus on the subject much closer than it original can. This works because our subject distance is very much reduced. Now, one thing you have to realise that consumer digital cameras cannot achieve the level of bokeh effect that DSLR has. For consumer digital cameras, your Real focal length is very small, i.e. 7.8 (W) – 23.4 (T) mm for A80. Although on specifications, it states that the camera's 35mm film equivalent is 38 (W) – 114 (T) mm. This is not your real focal length. What it is saying is the magnification you achieve that is comparable to a 35mm film equilvalent camera. I hope I didn't confuse you on this. Take for example we assume that a good bokeh effect is acheivable at 80mm f2.8 on a SLR/DSLR. You will quickly realise that consumer cameras like a80 does not have a real focal length at 80mm! A80's maximum focal length is only 23.4mm. Therefore, the current consumer digital cameras will never match up to the bokeh ability of DSLRs unless they start making them with larger focal lengths which means requiring a larger CCD which means larger lens which means higher costs. You get the picture. Conclusion With all these concepts in mind, you will be able to change the DOF by altering any of the factors be it through your camera's inherent ability or through add-on accessories. Phew, I think this is my longest post in Clubsnap. Hope that it helps.

21st November 2003	#4
theITguy Senior Member Join Date: Sep 2003 Location: In this small world Posts: 2,042	Thanks, learn something today too

22nd November 2003	#6
johnyu Member Join Date: Nov 2003 Location: Melbourne, Australia Posts: 316	sabre, well done!