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fstop on P&S's does not influence depth of field
I was playing around with a point and shoot that had some Aperture control. I thought that it would influence the depth of field but the sales men told me that it only lets more light in....or less light in depending on your setting but unlike a real aperture lens it will not affect the depth of field. I didn't know that till now and I wondered what all the fuss was about point and shoot cameras with manual controls....guess they are not real manual controls after all...

Comments (20)

It certainly does influence depth of field. But because of the small sensor, you are seeing greater depth of field so the differences at focusing distances other than macro may be so minute that you won't see a difference..

Larry Bermanhttp://BermanGraphics.com..

Comment #1

... and perhaps what the salesman said is what someone taught him too. (And yes that's scary but it's also reality in big-box camera seller world).

I've actually seen articles on the web that address depth of field on small sensor cameras. I just can't recall where..

Good luck with your purchase..

'Nice pen, bet you write good stories with it.'..

Comment #2

But also, manual control is just that, manual control. Some users want to be able to have direct control over their exposure. Manual control isn't strictly to obtain a specific DOF...

Comment #3

Larry Berman wrote:.

It certainly does influence depth of field. But because of the smallsensor, you are seeing greater depth of field so the differences atfocusing distances other than macro may be so minute that you won'tsee a difference..

In theory at least, a couple of ND filters (+1 and +2) could substitute for a diaphragm in a compact. They typically have an aperture range of only three stops (e.g. f/2.8 to f/8) so those two filters used together, separately, or neither, could provide the whole range of "apertures". The physical aperture and therefore the depth of field would remain constant..

A fully auto camera with no manual controls wouldn't need that much complexity. It could use a single +3 ND filter and rely on shutter speed and/or ISO speed to achieve the in-between steps. The unsophisticated user would probably never know..

Whether this has actually been implemented in any real-world camera, I have no idea...

Comment #4

All I can say is that using your P&S camera in Aperture priority will in fact have great influence in DOF. Play around with it and you will see. I had a Fuji S3100 and only used in in A mode with Fstop's of 2.1 - 5.4 - and 8. After figuring out how to use it, was always able to control my DOF in every picture (limited of course)..

Hope this helps.

Mars..

Comment #5

Aristoc wrote:.

I was playing around with a point and shoot that had some Aperturecontrol. I thought that it would influence the depth of field but thesales men told me that it only lets more light in....or less light independing on your setting but unlike a real aperture lens it will notaffect the depth of field. I didn't know that till now and I wonderedwhat all the fuss was about point and shoot cameras with manualcontrols....guess they are not real manual controls after all..

That's true of some, but not all P&S. Very few have a fully variable aperture like an SLR lens does. Some have two stops, maybe 2.8 and 5.6. Some use a ND filter for the same purpose. The latter are what the salesman is referring to..

Because of the small sensor and correspondingly small lens, P&S cameras have far more DOF than SLR's. If your purpose is to get everything in focus, that's great. If you intend to create an out-of-focus background, you generally need a larger aperture, like that on DSLR lens..

Some P&S have real manual controls, but can only control what the lens offers, which generally doesn't include a fully variable aperture..

And, I mean larger aperture, not aperture ratio. A 50mm f/2 lens has a 25mm aperture. A 7mm f/2.8 lens has a 2.5mm aperture...

Comment #6

Aristoc wrote:.

I was playing around with a point and shoot that had some Aperturecontrol. I thought that it would influence the depth of field but thesales men told me that it only lets more light in....or less light independing on your setting.

On this, he is absolutely correct. An Aperture is nothing more than the opening within the lens itself. Smaller numbers (F-stop:1.4 - 2.0 -2.8 - 3.1 - 4.0 - 5.6 -etc)being a larger opening, than the larger number..

Its confusing, I know..

What I tell my kids is to think of those numbers as how much of the picture is "in-focus", as mesured in Inches -Feet - Miles.

Now, imagine a long, white picket fence, starting at yoru toes & running on into Inifinity. Way down the line of pickets, sets a beautiful bird. You focus on the bird. If you choose F-stop 1.4,- which is only 1.4 ft, then the bird will be "in-focus" and 7-9 inches on each side of the bird..

Here's why..

With a very large aperture opening within the lens, 1.4, the light from the bird,hits the senor, which is adjusted for the perfect exposure of that focus spot..

The aperture is huge, 1.4, so the light from the pixckets closer to teh camera than the birds picket, had far to much time to hit teh cameras sensor, so they get progessively blurrier, as the stretch away from the birds picket. Remember, teh birds picket is the one for which we set our shutter speed, once we decided on our desired apeerture of 1.4..

What about those pickets that are farther away, than our birds picket?.

Well, since we set our shutter speed to gives us perfect exposure for the bird, those pickets are going to be blurry becuase we do not get enough light form them, to render them accurately...

Our aperture opening is very large, 1.4, so the light is not compressed any..

Compressed light?.

Hmm.

Think of a funnel. Any funnel will do..

Now, if we make our aperture opening very small, just like the end of a funnel, yet the opening iof the funnel s very large (say the entire wolrd) what happens?.

We compress the light , from the closest subject, with that of the farthest subject matter, so that light, form both objects near AND far, hit the cameras sensor at about the same time. Whcih makes the all appear to be in perfect focus..

SO, thinking of aperture numbers as inches-feet-miles, I want to get a Scenic of the Grand Canyon. I select aperture F-22. A ver very tuiny opening. Which acts a sfunnel, forces all the light from outside my camera to hit hte sensor, at the exact same time..

Now, this is greaty simplied but in essence thats how aperture controls the amount of light allowed in..

But unlike a real aperture lens it will not.

Affect the depth of field. I didn't know that till now and I wonderedwhat all the fuss was about point and shoot cameras with manualcontrols....guess they are not real manual controls after all..

Here, he is drastically wrong.Aperture affects DOF. Periood..

However, there are also other things that detemine Depth of Field, One being sensor size. P&S have a very small sensor. they also have very small lenses..

Seriously, think of how wide that lens is, one that little camera. Now think of one of those huge white professional lenses..

Remember, the larger number, allows more light, gives us shallower DOF?.

Well, when the difference from your cameras largest opening, to it's smallest opening, is not measureable, then you are not goign to really notice a difference in yoru image..

Simple as that..

How much differene do you think is there, between max-min on the little P&S lens, versus a huge white one?.

Thats why P&S appear to not have any DOF..

Dave PattersonMidwestshutterbug.com'When the light and composition are strong, nobodynotices things like resolution or pincushion distortion'Gary Friedman..

Comment #7

Hopefully the sales man was right but I just misinterpreted what he was trying to say...

Comment #8

Steve Balcombe wrote:.

A fully auto camera with no manual controls wouldn't need that muchcomplexity. It could use a single +3 ND filter and rely on shutterspeed and/or ISO speed to achieve the in-between steps. Theunsophisticated user would probably never know..

Whether this has actually been implemented in any real-world camera,I have no idea..

Yes indeed it has. Right now I'm sorry to say that I can't quote which ones. But I've seen an instruction manual for at least one camera where it is explicitly stated that the camera has an ND filter for exposure purposes rather than a variable aperture. There is some logic to this approach, as the effects of diffraction can be avoided.Regards,Peter..

Comment #9

Most P&S cameras have an aperture and it's effect on both DOF and diffraction can be observed. The difference is in degrees between a small sensor camera and a large sensor camera but it is testable and observable none the less..

There also have been P&S cameras that have used an ND filter, usually just one but they were typically had full auto exposure with no manual controls...

Comment #10

Your sales guy should learn something about photography as he's very wrong about this basic truth..

P&S cameras usually have much deeper DOF both because of slower lenses and smaller sensors so you may not notice the effect of aperture changes have on DOF but there is only one DOF formula and all optics follow the same rules..

RegardsJim.

Http://www.flickr.com/photos/jimboutilier/..

Comment #11

This isn't true at all AFAIK... I've played around a lot on my Canon S45 in the years before I finally got a DSLR, and adjusting the aperture most certainly DID make a difference to the depth of field..

Perhaps to the untrained salesman it SEEMED as though it didn't make a difference since compact cameras typically have a far larger depth of field to begin with...

Comment #12

And we control it by changing the camera's aperture. But only if the aperture is really big in some overall sense, not as a ratio, say to the focal length of the lens? Perhaps the white color of the really big lenses has something to do with it as well..

Really, I found your post to be baffling...

Comment #13

I'm afraid I must agree... I have no idea what Midwest is talking about.....

Comment #14

Thanks... after decideing to live a life of the meger... and going Pro about 9 years ago... I got WAY to tech... This was a WELCOME relief and a fresh look for me... understading something with out being able to explain it to someone else is a tough thing to live with...



Judson CrosslandMember NPSACL Photohttp://www.aclphoto.com.

Don't Fear the space between your reality and your dreams... if you can dream it... you can live it!.

Midwest Shutterbug wrote:.

Aristoc wrote:.

I was playing around with a point and shoot that had some Aperturecontrol. I thought that it would influence the depth of field but thesales men told me that it only lets more light in....or less light independing on your setting.

On this, he is absolutely correct. An Aperture is nothing more thanthe opening within the lens itself. Smaller numbers (F-stop:1.4 - 2.0-2.8 - 3.1 - 4.0 - 5.6 -etc)being a larger opening, than the larger number..

Its confusing, I know..

What I tell my kids is to think of those numbers as how much of thepicture is "in-focus", as mesured in Inches -Feet - Miles.

Now, imagine a long, white picket fence, starting at yoru toes &running on into Inifinity. Way down the line of pickets, sets abeautiful bird. You focus on the bird. If you choose F-stop 1.4,-which is only 1.4 ft, then the bird will be "in-focus" and 7-9 incheson each side of the bird..

Here's why.With a very large aperture opening within the lens, 1.4, the lightfrom the bird,hits the senor, which is adjusted for the perfectexposure of that focus spot..

The aperture is huge, 1.4, so the light from the pixckets closer toteh camera than the birds picket, had far to much time to hit tehcameras sensor, so they get progessively blurrier, as the stretchaway from the birds picket. Remember, teh birds picket is the one forwhich we set our shutter speed, once we decided on our desiredapeerture of 1.4..

What about those pickets that are farther away, than our birds picket?.

Well, since we set our shutter speed to gives us perfect exposure forthe bird, those pickets are going to be blurry becuase we do not getenough light form them, to render them accurately...

Our aperture opening is very large, 1.4, so the light is notcompressed any..

Compressed light?.

Hmm.

Think of a funnel. Any funnel will do..

Now, if we make our aperture opening very small, just like the endof a funnel, yet the opening iof the funnel s very large (say theentire wolrd) what happens?.

We compress the light , from the closest subject, with that of thefarthest subject matter, so that light, form both objects near ANDfar, hit the cameras sensor at about the same time. Whcih makes theall appear to be in perfect focus..

SO, thinking of aperture numbers as inches-feet-miles, I want to geta Scenic of the Grand Canyon. I select aperture F-22. A ver verytuiny opening. Which acts a sfunnel, forces all the light fromoutside my camera to hit hte sensor, at the exact same time..

Now, this is greaty simplied but in essence thats how aperturecontrols the amount of light allowed in..

But unlike a real aperture lens it will not.

Affect the depth of field. I didn't know that till now and I wonderedwhat all the fuss was about point and shoot cameras with manualcontrols....guess they are not real manual controls after all..

Here, he is drastically wrong.Aperture affects DOF. Periood.However, there are also other things that detemine Depth of Field,One being sensor size. P&S have a very small sensor. they also havevery small lenses..

Seriously, think of how wide that lens is, one that little camera.Now think of one of those huge white professional lenses..

Remember, the larger number, allows more light, gives us shallower DOF?.

Well, when the difference from your cameras largest opening, to itssmallest opening, is not measureable, then you are not goign toreally notice a difference in yoru image..

Simple as that..

How much differene do you think is there, between max-min on thelittle P&S lens, versus a huge white one?.

Thats why P&S appear to not have any DOF..

Dave PattersonMidwestshutterbug.com'When the light and composition are strong, nobodynotices things like resolution or pincushion distortion'Gary Friedman..

Comment #15

Zadam wrote:Perhaps to the untrained salesman.

Two words for you to ponder....

Best Buy....

Judson CrosslandMember NPSACL Photohttp://www.aclphoto.com.

Don't Fear the space between your reality and your dreams... if you can dream it... you can live it!..

Comment #16

Jim Boutilier wrote:[snip].

There is only one DOF formula andall optics follow the same rules..

Really? Only one? Are you sure about that? Before you answer, remember that the CoC is part of the DoF formula...

Comment #17

Dave_s93 wrote:.

Jim Boutilier wrote:[snip].

There is only one DOF formula andall optics follow the same rules..

Really? Only one? Are you sure about that? Before you answer,remember that the CoC is part of the DoF formula..

Yes... in it's full form the DoF calculation takes account of the CoC size and how it is influenced by viewing distance, sensor size and print size etc - see for example.

Http://www.cambridgeincolour.com/tutorials/DOF-calculator.htm..

The simpler 'standard' calculators, like the frequently-quoted one athttp://www.dofmaster.com/dofjs.html.

Just make standard assumptions about the CoC size (a 10 x 8 print viewed from a distance of one foot is a common assumption), but it is the came calculation underneath..

Best wishesMike..

Comment #18

Judson:.

Please understand that Midwest was (we hope anyhow) speaking only metaphorically. The explanations he gives have nothing to do with how light, lenses or sensors actually perform, and are not the reasons that focus varies with subject distance..

Davehttp://www.pbase.com/dsjtecserv..

Comment #19

I should've just posted to a link to this sitehttp://www.largeformatphotography.info/articles/DoFinDepth.pdf.

If a person is smart enough to see the obvious, they are smart enough to know what I was attempting..

I felt it more important to get the OP started on Aperture-DOF relationship, rather than impress & confuse..

My mistake.I thought this was a newbie forum..

Dave PattersonMidwestshutterbug.com'When the light and composition are strong, nobodynotices things like resolution or pincushion distortion'Gary Friedman..

Comment #20

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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