Napioa - Wind Origins

Napioa - Wind Origins
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Why is it that on compact digital cameras the aperture never seems to go any smaller than about F8 ? Even on high-end compacts such as the Canon G10 or Panasonic LX5. Is there some practical or physical limitation due to the size of the camera or the sensor which prevents this from being possible?

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Diffraction is the key issue here. While my Nikon COOLPIX S9900 has full aperture control down to 1/6 of a stop, stopping down past about f/5.6 or so visibly degrades sharpness. The effect is especially noticeable towards the wide end of the lens where faster aperture stops are available (the difference in sharpness between f/5.6 and f/8 is dramatic especially at close focusing distances). Stopping down past f/8 (which the camera doesn't allow, as mentioned by your question) would only make things worse. – bwDraco Jan 3 at 20:44
up vote 25 down vote accepted

Although the relative aperture numbers — the ƒ stops — are the same regardless of format, the actual focal lengths of the lenses on small cameras are quite low: 5mm or 6mm at the wide end. That in turn means that the real aperture is small, which means the diffraction limit kicks in sooner, reducing sharpness as one stops down.

The smaller format also means that depth of field is hugely increased even at the widest-available apertures — even wide open at f/2.8, a camera like the Canon G10 has an infinite depth of field if you're focusing farther away than a few feet. So, there's not much difference in that aspect of changing aperture, so from that point of view there's no point even bothering. And that's presumably why there's usually not many choices besides wide open and one closed-down stop like f/8. (Because everything is small, and competitive price pressure significant, adding the mechanics for more intermediate stops is easily deemed not worth it.)

The other aspect of a smaller aperture is, of course, controlling exposure in bright light, without artificially dropping ISO beyond the sensor base or using very high shutter speeds. Some compact cameras actually use a dark neutral-density filter instead of closing down the aperture, specifically to avoid issues with diffraction.

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Thanks for your very comprehensive answer - I never actually knew about the depth of field effect (or lack of effect above a certain distance) on these cameras. I have often wondered why I didn't seem to get the expected shallow depth of field with my LX5 despite often shooting with the aperture wide-open at F2. – Matthew Dresser Feb 25 '11 at 13:54
    
I had the same doubts about my RX100 with f/1.8 (: – igorsantos07 Jun 2 '13 at 15:53
    
Sorry if I recover this old post: does the aperture with a smaller sensor mean the same in terms of shutter speed (with same ISO)? – clabacchio Jul 11 '13 at 22:14
    
    
Not all compacts lack proper aperture control. My Nikon COOLPIX S9900 has a 6-blade diaphragm with aperture control down to 1/6 of a stop. – bwDraco Jan 3 at 20:23

Yes, it's a physical limitation due to the size of the sensor (and thus the size of the individual photosites) that means that diffraction becomes a limiting factor sooner than it does with DSLRs, hence the aperture doesn't go smaller than f/8.

Older compacts do have a larger range, my old Fuji Finepix s602 went down to f/11

see also:

What is a "diffraction limit"?

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The biggest reason for smaller apertures is to increase the depth of field at a given focal length. Point and shoot cameras, with their small sensors, already have huge depth of field when compared to their larger cousins at any given focal length, so the smallest aperture is going to be selected to maximize depth of field and retain sharpness in the image (too tight an aperture leads to diffraction and loss of sharpness). So, it's a balancing act.

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How does sensor size influence depth of field? Isn't it really that small sensor size ==> small focal length ==> small depth of field? – whuber Feb 25 '11 at 5:42
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@whuber it's small sensor size ==> small focal length [to get normal coverage] ==> large depth of field – gerikson Feb 25 '11 at 6:04
    
@geriksen Sorry, and thank you; I meant to write "large depth of field," but the lure of repeating all the "smalls" (and the late hour) distracted me! – whuber Feb 25 '11 at 6:12

And don't forget that many of those cameras have no adjustable aperture at all. They're always shooting wide open, any adjustment that might happen being done through changing the sensitivity of the sensor, no moving parts required.

These cameras aren't designed for people with an interest in photography, so there's no need for things that can be adjusted by the operator. In fact your average user doesn't want to adjust anything, just point and click, and the cameras are designed with that in mind.

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l can only be brief, this is how I have done it: I took an old 2 megapixel pocket-sized digital camera, carefully stripped the objective lens and just replaced the original aperture which has a 3mm hole with a ultra thin brass shim of 0.05mm thick with a precise hole of 0.33mm at the center.

As we know sensors do permit light fluctuations but will claim more exposure time. I am not an expert in such, but the results are good. All I can say is do not go below a 0.27mm hole because the entry of light will suffer and cause soft blur .

I have also done this with a cellphone camera and it works very well , It offers very good pictures with extraordinary depth of field - very useful for miniature landscape. For example 1 sq foot of miniature landscape will look as big as 1 acre of land .

Unfortunately manufacturers do not want to see it because it dose not suit their plans: they want customers to be always buying new cameras hoping that the new product may have these features .

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So you invented the pinhole camera :) I'm pretty sure it has a good list of funny/not-wanted effects that lenses normally correct. – Olivier Apr 12 at 20:41
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This reads like a followup to your previous answer. Perhaps it would be better to edit your answers together into a single answer and delete one of them. – scottbb Apr 12 at 20:46

It's a business decision, because you can have very small apertures on cameras - yes as small as 0.33 mm or f/80 with absolute sharpness from 12 mm to infinity.

I say so through experience. The only setback is that it needs 4x more exposure during the day time and is very difficult at night without a strong light and a steady hand. The diffraction of light begins at 0,27 mm aperture or f/92. Today technology allows such but manufactures are not interested in any improvements because it clashes with the set protocol which is not to satisfy the customers but their own ambition.

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Your answer lacks very important information to be useful. What are your sources ? What is the sensor you are using as an example ? What is the focal length ? What is your definition of absolute sharpness, how do you compute it ? What are your references of camera/sensor cost ? – Olivier Apr 11 at 17:29

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