Ecriminal wrote:.
I'm planning to buy a Digital Camera, I'm a beginner but I know thebasics (Aperture, Focal length, ISOs, shutter speeds, DOF .. etc)..
I'm taking into consideration a Point and Shot Cam because my budgetis around $300 which won't allow me to put my hand onto a DSLR. So Ichoosed the Canon A640, It's good, It's easy and It's highlyrecommended by the dpreview..
My question is, I check it's features and found that the aperture isonly F2.8-F4.1!! Can I go behind this? I mean if I need to shot inF11 or F8 for example, could I do so? in any circumstances?.
I checked in the Canon G7 that it's lens is F2.8 - F4.8 but when itcomes to aperture I found it F2.8 - 8 (Wide) F4.8 - 8 (Tele)!!.
Confusing enough, eh?.
Yeah the convention is to include the F2.8-F4.8 in the lens name, and include the range F2.8 - 8 (Wide) F4.8 - 8 (Tele) in the specifications of the lens. (I am using the examplel of the G7 lens in both cases). So the F2.8 to F4.8 is the range of biggest aperture going from wide angle to full telephoto of the lens. F2.8 to F8 is the range of apertures you can chose (or the camera choses) at specific focal lenghts (eg wide, which for this camera starts somewhere in the 30s mm)..
It can certainly be confusing for those who are not familiar with the convention and history of this. There are some variations on how this is done which may help confuse things even more..
What may make be contributing to the confusion is that the F-numbers are fractions, eg F/2.8, F/4, so basically the smaller the number, the bigger the opening. So a smaller number indicates a bigger lens opening, which may seem counter-intuitive at first. For easier typing a lot of people write just F2.8 instead of F/2.8.
Comprehensive 2007 speculation and predictions: http://1001noisycameras.blogspot.com..
Ecriminal wrote:.
I'm planning to buy a Digital Camera, I'm a beginner but I know thebasics (Aperture, Focal length, ISOs, shutter speeds, DOF .. etc)..
I'm taking into consideration a Point and Shot Cam because my budgetis around $300 which won't allow me to put my hand onto a DSLR. So Ichoosed the Canon A640, It's good, It's easy and It's highlyrecommended by the dpreview..
My question is, I check it's features and found that the aperture isonly F2.8-F4.1!! Can I go behind this? I mean if I need to shot inF11 or F8 for example, could I do so? in any circumstances?.
Don't worry about it. The higher values (around f/8, say) are ALSO available on the lens. You can use them in good bright light, when you want greater DoF..
The aperture value quoted is just the maximum ... the one that lets in most light when the light is dim. This is the aperture value that is most useful to know..
I checked in the Canon G7 that it's lens is F2.8 - F4.8 but when itcomes to aperture I found it F2.8 - 8 (Wide) F4.8 - 8 (Tele)!!.
Confusing enough, eh?.
Again, don't worry about it. It is not confusing, really..
All you must do is remember that the higher numbers mean smaller holes where apertures are concerned..
Why are there two numbers? Well......
There are two different aperture values for the different focal lengths because the aperture size is expressed *relative* to the f-length.... whatever that is..
The relationship is.... f/number..
This is why old time photographers write apertures with the forward slash... /[ f/5.6 ] ... to show that it is a division sum !! .
Therefore, as the f-length gets greater towards long end of the zoom range, the size of the aperture reduces proportionally, meaning it lets in somewhat less light to the sensor... (see above)..
Does this also mean that tele shot are easier taken in bright light?.
Yes, it does! Regards,Baz..
You won't get f/11 or more with that camera. At f/8, the aperture is already a tiny pinhole, any more and you get diffraction. I don't know of any digicam that can stop down past f/8, for the same reason..
It won't be an issue, at f/5.6 you have pretty much everything in front of the camera in focus already... (G).
Crime Scene PhotographyA small gallery of personal work: http://picasaweb.google.com/PID885..
But I mean I could choose for example an F/8, I know it will make diffraction, but am I allowed to do so? or will it screw up and spit the sensor out at my face ?..
Ecriminal wrote:.
But I mean I could choose for example an F/8, I know it will makediffraction, but am I allowed to do so? or will it screw up and spitthe sensor out at my face ?.
I wondered if those explanations would reduce your confusion...or just make it worse. Let me try....
There ARE zoom lenses that have a constant maximum aperture (minimum f/number). For those lenses, the convention is to state the FL range and give the single max aperture (for example, 2mm-40mm f/2.8). These lenses are not common for still cameras...very common for movie and video cameras where it's not tolerable to have the exposure change as the lens is zoomed..
Most still camera zoom lenses have a variable maximum aperture, thus when specifying the lens, the max aperture at both FL extremes are quoted (for example, 18mm-130mm f/2.8-4.8). Normally, the minimum apertures are not quoted, as they are assumed to be as small as is feasible (considering diffraction). For short FL lenses, as used on small-sensor cameras, the min aperture is often as low as f/5.6. For big-sensor cameras it often extends to f/32..
When reading specs, a good, more expensive lens typically has:.
1. A larger aperture (smaller f/number).2. A larger zoom range.3. Better IQ (but this is difficult to quantify in specs).4. A faster focus motor.5. Vibration reduction (or whatever the mfg.
Is made of metal, instead of plastic..
The other specs don't cost much to make (ie, a white lens has the same mfg. cost as a black lens), therefore, you should sorta ignore them..
In your specific case, the lens is NOT limited to the max openings stated. It will be able to be stopped down w/o damage to you or the camera..
Be aware that the highest IQ is typically achieved at some aperture near the middle of the range. For example, a lens that can be adjusted from f/2.8 to f/8.0 will probably have the highest resolution and minimum aberations at approx. f/4.0 or f/5.6. There are sites that test SLR lenses and you can use them to assess the IQ of a prospective lens before you purchase it..
Charlie DavisNikon 5700 & Sony R1HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..
Ecriminal wrote:.
But I mean I could choose for example an F/8, I know it will makediffraction, but am I allowed to do so? or will it screw up and spitthe sensor out at my face ?.
The smallest aperture you can select yourself on the A640 is F8, but according to the manual, in auto mode only, F11 or F16 may be selected under certain circumstances, unfortunately for some reason not possible manually though...