CCD Sizes

[megascriler]

I'm a little bit confused. What is the size of a 1/2.5" image sensor? Do I take 1 divide by 2.5 to find the size in square inches?

And cameras such as the Panasonic FZ series have apertures of f2.8 throughout the zoom range, but why is it that the camera is still able to take landscape or pictures requiring large DOF yet still clear with just f2.8?

 

[user111]

read dpreview.com they explain it there

 

[reno77]

Here you go, your answer is Q.10.
http://www.clubsnap.org/display.php?file=articles/photography101/photography101.html

10. Why is my digicam having deeper DOF at the same focal length and f-stop when compare to an SLR?

Anybody like to answer this? Since the sensor size digicam is much smaller then the standard 35mm size on the SLR, its lens has a shorter “equivalent focal length” then the SLR’s. Remember from above, the aperture size is (focal length)/(f-stop value)? Now at f/8, the actual aperture size on the digicam is much smaller then that on the SLR, resulting a deeper DOF.

 

[Drudkh]

http://www.dpreview.com/learn/?/Glossary/Camera_System/Sensor_Sizes_01.htm

 

[AncientMariner]

I'm a little bit confused. What is the size of a 1/2.5" image sensor? Do I take 1 divide by 2.5 to find the size in square inches?

And cameras such as the Panasonic FZ series have apertures of f2.8 throughout the zoom range, but why is it that the camera is still able to take landscape or pictures requiring large DOF yet still clear with just f2.8?

1st Qn: Don't know how to calculate the size. However, I have a FZ with a 1/2.5 sensor. It's size is said to be 7.176 x 5.319 mm.

2nd Qn: "Hyperfocal focusing" can be used to get max DOF. See:
http://www.synvis.com/hyperfoc.htm

 

[megascriler]

Can someone kindly please simplify the hyperfocal article? And it mentions f22, I'm referring to f2.8 still getting sharp results. Please help.

 

[Splutter]

The article isn't really as applicable to point and shoot cameras with much smaller sensors. DOF is dependent on many factors.
- Sensor size
- Focal length
- Aperture
- Distance of subject to sensor

The bigger the sensor, the shallower the DOF (all else remaining constant).

For the landscape shots you refer to, as the subject is far away (infinity), most things around that distance will be focused no matter you use f2.8 or f22 (pics are usually sharper though at bigger aperture numbers though). However, if you try doing landscape shots with an object in the foreground, etc 10cm away, there will be a compromise. I don't think its possible to have the subject and a mountain 10km away focused at the same time if you use f2.8.

 

[megascriler]

Haha yes. Thank you for your answer.

 

[pai]

I'm a little bit confused. What is the size of a 1/2.5" image sensor? Do I take 1 divide by 2.5 to find the size in square inches?

And cameras such as the Panasonic FZ series have apertures of f2.8 throughout the zoom range, but why is it that the camera is still able to take landscape or pictures requiring large DOF yet still clear with just f2.8?

1) i think 1/2.5" refers to the diagonal. so a 1/2.5 (= 0.4) inch sensor measures 0.4 inches from top left to bottom right corner. or top right to bottom left.

2) i agree with the explanation reno77 found.

the f-stops and focal lengths on compact cameras with smaller than full-frame sensors are actually only *relative* figures - ie a lens with the same focal length and aperture ratings on an FZ will be much much smaller than a lens with the same ratings on a full-frame slr.

so when a lens on a small camera is set at f2.8 (remember, the bigger the number, the smaller the aperture), the actual aperture size is still much smaller than an slr set at f8 or even higher. so the depth of field of a small camera at f2.8 would be like the dof of a large camera stopped down to high f numbers like f16