woodsmitty Loc: Bruderheim, Alberta Canada

As I understand it f 8 on a 35mm camera or on a crop camera is a hole the same size. F stops are a lens only calculation and do not change as the film/sensor size changes.
If my understanding is correct then why do old film cameras have f stops ranging from f 3.5 to f 22 or f 32 and P&S and bridge cameras have typical ranges like f 2.7 to f8? Why do these digital cameras not have larger ranges of f stops?
All help you can give me to clear up this will be appecated as I searched this site and google and could not find an answer.

Danilo Loc: Las Vegas

Great question! I'll jump in with what may turn out to be only a partial answer.
I'm sure you've noticed that the lenses on P&S and Bridge cameras are physically smaller than DSLR lenses. On a P&S you may have an 8X or 10X zoom on a camera that's smaller in its entirety than even a 3X zoom lens by itself for a DSLR. The diaphragm mechanism that creates your "f-stops" is so tiny that it cannot be as complex as the diaphragm in the larger DSLR lens.
I'm also sure there are cost considerations.
They may figure the average P&S shooter will be covered adequately with this limited range.
Also, very small apertures can bring out undesirable qualities in a less than perfect lens.
I hope I won't be the only responder, as there may be other good points I am missing.

woodsmitty Loc: Bruderheim, Alberta Canada

Thank you. I never considered the physical size limitation regarding the f stop. I still wonder why the SX40 that has a fairly large lens diameter only goes to f8. Does this truly limit DOF on these cameras?
My S700 goes up to f 13.6 why not the SX40?

rebride

Bridge cameras because of small sensor do not need more than f/8 as far as DOF is concerned. Easily = f/22,f/32.
As a sensor gets smaller DOF expands for any given f stop/lens.
Bridge cameras can have large DOF even wide open. Sometimes (often??) a problem when you want a shallow depth of view.

woodsmitty Loc: Bruderheim, Alberta Canada

I did not know that the sensor size affected the DOF in this way. So that would mean that the max opening of f 2.7 would really be more like f 5.6? That explaines a lot that I was wondering about when I viewed my photos. The lack of shallow DOF in my close ups for example.
I wonder if diopter lenses/filters would cure the need for shallow DOF?

steve40 Loc: Asheville/Canton, NC, USA

Most bridge cameras, will suffer some defraction even at F4. So why then worry about F8, much less anything above..

rebride

That would be an interesting discussion, the 'cure'. Just be ready for the BSLrers to bust in.

Check out Steve40's flower shots via his website.

photocat Loc: Atlanta, Ga

DOF is also controled with viewing distance and the focal length of the lens in use.

jim charron Loc: Ontario Canada

On my sony hx9v point and shoot camera,it only has two settings in manual mode ; a light one for dark pictures and a dark higher setting for if the area is too bright.
But, this setting is fake, in that they just provide a mask to
reduce the light, and is not doing anythingwith the lens. Crap, oh well, do with what you have....

Roy Hakala Loc: Red Wing, MN

It is not really the sensor size that increases the depth of field; it is the lens used with the smaller sensor. When you go to a smaller sensor with a given lens, the sensor misses the edges of the projected image. This is what the "crop sensor" discussion is all about. Manufacturers compensate for this by installing lenses with shorter focal lengths. Then the whole picture fits on the sensor. But shorter focal length lenses have more depth of field, just as a 28-mm wide-angle lens on an old film SLR camera had much more depth of field than a 150-mm telephoto. The iPhone 3 had a tiny sensor and its fixed-focus lens produced an incredible depth of field.

Diopter filters only change the focusing range and do not really affect depth of field. Neutral density filters would cut down the available light and force the camera to go to a wider aperture, but depth of field would still be the same at that maximum aperture, with or without the filter. The only add-on that would reduce the depth of field would be a tele-adapter. I use one with my Nikon Coolpix P7000 at times.

My favorite subjects are landscapes, which generally call for more depth of field. I prefer cameras with smaller sensors and their appropriate lenses for that reason.

jenny Loc: in hiding:)

Oh,oh,this reminds me of a question to me recently by someone asking what i thought at first was a strange questiion: "Is there a numeric value to an f-number?" Yes, of course,always! What prompted such a question? If we stood next to each other viewing the same object,you with a full frame DSLR and I with a bridge camera,we would both have the same exposure when shooting with the same f-number,
even though obviously the apertures were not the same size.
Did he really want the answer though? The numerical value of the aperture is determined by dividing the focal length by the diameter of the effective aperture. (That explanation takes some thinking, i thought,and a bit more math than we are used to doing in our heads.) Finally I had to explain it is all about focal length after all....
A lens has to be round, and large enough to cover the whole area of a rectangular film frame or sensor. It turned out the inquiry arose because of looking aat the full frame DSLR and then an iphone with a 2.8 lens. The focal length
on a slender shallow P&S is of course limited by its design.
The focal length is increased by a zoom lens which did not exist in the iphone. The amount of light entering a small
lens can be the same as that entering a larger lens but the actual aperture is smaller on the little camera because of the very short distance from lens to sensor.We just can't have everything can we? Similarly,those who used the larger med. format cameras were getting the same field of view as the users of 35mm cameras when the 35mm camera had a 50mm fl
lens but the larger camera had 80mm lens. I thought i would wind up in knots or turn inside out trying to give a simple explanation to a strange question,and not sure of having done it successfully then or now.

punene

what is a bridge camera ???

photocat Loc: Atlanta, Ga

a camera between a point and shoot and a full DSLR.

Can't change lens.

steve40 Loc: Asheville/Canton, NC, USA

Now don't be pulling his leg, you know its a camera for taking pictures of bridges. :roll:

jim charron Loc: Ontario Canada

Oh that's simple, I got this one boys.....

its a camera with a bridge on it ! :mrgreen:

kidding, its a camera that is in between and small point and shoot and a full DSLR.

So larger than a point and shoot, smaller/lighter than a dslr. its an in betweener.