Understanding resolution with my cell phone camera

[wags]

I have a question for the experts out there. If I take a picture with my cell phone camera I get a nice sharp image, say of a flower. My understanding of resolution is that if I decrease the size of the lens aperture I decrease the resolution resulting in a blurry image.

To test this, I take a small piece of paper and place it in front of the camera lens. I then poke a small hole in it (smaller than the lens diameter) and take a picture of the same flower. The flower (or whatever it is) is indeed blurry. I have tried this several times with several objects. In fact, this method can be done by simply sliding a piece of paper in front of the lens until it is almost covered. Same effect.

My question is this: Am I truly seeing a resolution decrease with this method or is the camera electronics causing this blurriness as I decrease the aperture size? (you can try this with your cell phone camera. Does this work for other cameras too?) Thank you for your help on this!!

[Black Pearl]

What you're seeing is the camera with a carefully designed, carefully engineered, carefully built lens trying to take a picture through a scabby bit of paper with a random hole poked through it

[royphot]

The edge of your bit of paper will be within the picture and will no doubt have rough edges and be well out of focus, this will cause blurring and spread light (diffuse) over all of the frame. If you don't believe this, try holding a similar piece of paper in front of the lens of a well focussed projector. Blurry image all over the screen.

[pnodrog]

I think your understanding of optics, resolution and electronics is truly unique....

[TonyW]

Reducing the aperture of the lens would normally be expected to improve the sharpness until diffraction effects become important. That's probably not relevant here.

When you put the paper in front of the lens, the camera will try to focus on the paper, probably unsuccessfully if it is close, and upset the focus on the flower and make it blurry.

It is not clear what the object of your experiment is.

[Dave Humphries]

Hi 'wags',

I have a question for the experts out there. If I take a picture with my cell phone camera I get a nice sharp image, say of a flower. My understanding of resolution is that if I decrease the size of the lens aperture I decrease the resolution resulting in a blurry image.

As a general rule, this is not true.

To test this, I take a small piece of paper and place it in front of the camera lens. I then poke a small hole in it (smaller than the lens diameter) and take a picture of the same flower. The flower (or whatever it is) is indeed blurry. I have tried this several times with several objects. In fact, this method can be done by simply sliding a piece of paper in front of the lens until it is almost covered. Same effect.

This is not a valid technique at all I'm afraid, you're not 'reducing the aperture' (of the lens) by this method.
You're just blocking and diffracting light getting to the lens.

My question is this: Am I truly seeing a resolution decrease with this method or is the camera electronics causing this blurriness as I decrease the aperture size? (you can try this with your cell phone camera. Does this work for other cameras too?) Thank you for your help on this!!

'No' to both, or all three, if you include trying this on other cameras.


Anyway - a warm welcome to the CiC forums from me.

Could you do me a favour please?
Could you click Settings (right at the top),
then Edit Profile (on left)
and put your first name in the Real Name field
and where you are (roughly) in the Location field,
then click the Save Changes button below and to right,
this helps everyone give you more personal and relevant answers - thanks in advance.

If you pop back to read these replies, try reading a few of the Tutorials linked above.
Unfortunately, the one most relevantly titled seems to be down at the moment, or I'd have put a link to it here for you.

Dave

[DanK]

Wags,

this forum, unlike most, has very well written tutorials introducing people to the basic concepts in photography. I suggest you read some of the ones under "concepts and terminology." They will explain, for example, the functions of the camera's aperture. Then post questions about things that are unclear to you, and we will try to answer them. That is both more efficient and more effective than our trying to re-create pieces of those tutorials on the fly.

Dan

[Shadowman]

If I were Wag, the question I'd be asking is "why can't the manufacturers provide its customers with answers about their technology; not just rudimentary specifications and examples of output?"

[xpatUSA]

I have a question for the experts out there. If I take a picture with my cell phone camera I get a nice sharp image, say of a flower. My understanding of resolution is that if I decrease the size of the lens aperture I decrease the resolution resulting in a blurry image.

My question is this: Am I truly seeing a resolution decrease with this method or is the camera electronics causing this blurriness as I decrease the aperture size?

Welcome, @wags,

You are the victim of Standard Photographic Vague (SPV) terminology. Please search the Internet to find the definition of 'resolution' and then send me $1 for every variation found.

'resolution' means all things to all men. It is right and proper here to NEVER put a qualifying descriptor in front of the word. If you do, you are in danger of being told to "get a life" and "go out into the Real World and take pictures", etc.

If resolution is defined as the number of pixels in MP that your camera is set to, then twiddling the aperture does not change the resolution.

If resolution is defined as the pixel pitch of your camera sensor, then ditto.

If resolution is defined as the contrast ratio (MTF) you get at the sensor, then twiddling the aperture does change the resolution.

The camera electronics do not cause this blurriness, it is purely optical in nature. Google <lens aperture diffraction> for more.

Hope this helps rather than confuses and please pardon the cynicism

[IzzieK]

Welcome to CiC, Wags...

[jcuknz]

On reading Wags first comment my thought was "Of course the wonderful camera is trying to focus on the paper and putting the subject out of focus" Cellphones/i-pads whatever are wonderful things but they have their limits in coping with what us humans give them