Couple of lens questions

[Mister_Pister]

Not owning an SLR yet I dont profess to have a huge deal of knowledge about lenses. I see people saying they have like a sigma 40-100 f5.6 or something. Is 5.6 the only apeture it can do? Or just like its optimum one?

Also me no comprende focal lengths at a guess im asuming the shorter the length e.g 20mm gives you a wider view then something at say 300mm?

 

[olv]

The aperture stated is the maximum aperture at the minimum focal length.

and yes, a small focal length means a wider angle of view.

 

[Joe T]

http://www.usa.canon.com/html/eflenses/lens101/focallength/

Useful for focal length comparison.

Once you get your head round that, someone will confuse you with all the talk of DSLR 'crop factor'!

The aperture stated is the widest (ie most amount of light) it can let in. The lower the figure, the bigger the aperture. Wide aperture lenses are bigger, heaveri and cost more (in general).

 

[Mister_Pister]

useful link thanks I do understand aperture already luckily was just wondering what it meant when stated on lenses

 

[aztechnology]

Usually a zoom lens will quote a range of maximum apertures.

eg a 24-85 F/3.5-4.6

means that the maximum aperture at 24 is F/3.5
maximum aperture at 85 is F/4.6

as you zoom throughout the range from 24-85, the Maximum aperture gradually decreases to f/4.6


if a zoom lens quotes a single number, it usually means that the lens has a fixed maximum aperture.

eg a 70-200 F/4

means that the lens has an Maximum aperture of F4 throughout the zoom range.

Primes just have the one maximum aperture (usually nice and wide) as they don't zoom.

Mirror lenses have a fixed aperture, say F/8. There is no way to control exposure on these lenses other than shutter speed.

 

[Mister_Pister]

but on these lenses can u generally stop down the aperture to about 22 or whatever or is there a maximum value on that too?

 

[xolotl]

but on these lenses can u generally stop down the aperture to about 22 or whatever or is there a maximum value on that too?

There is a maximum you can stop down to, can be up to f/32 but generally you wont want to use these extremely small apertures due to diffraction.

 

[Mister_Pister]

ah ok. I was just thinking for landscapes and so on to preserve more detail and increase DOF

 

[Johnny|lucidcomposure]

ah ok. I was just thinking for landscapes and so on to preserve more detail and increase DOF

Yeah a landscape shot should be shot from F16 - F22. These I suppose are ideal. (unless of course you are looking for something creative using depth of field)

 

[xolotl]

Yeah a landscape shot should be shot from F16 - F22. These I suppose are ideal. (unless of course you are looking for something creative using depth of field)

Not necessarily. Have a look at Hyper focal points and its surprising how low and aperture you can get away with.

http://www.barbeephoto.com/articles/hyperfocal/hyperfocal.htm

 

[Mister_Pister]

well I have been looking for something to push my rubbish F8 on my sony H1 to its maximum ill give that technique a try while im on holiday

 

[Johnny|lucidcomposure]

Not necessarily. Have a look at Hyper focal points and its surprising how low and aperture you can get away with.

http://www.barbeephoto.com/articles/hyperfocal/hyperfocal.htm

Interesting read thank you. I still wouldnt go anything down from F11 though. Personal preference.

 

[aztechnology]

but on these lenses can u generally stop down the aperture to about 22 or whatever or is there a maximum value on that too?

Technically, the low numbers are the maximum. They are quoted as ratios F 1/4 - F 1/32, but the 1/ often gets left off. So the Big numbers are the minumum and the small numbers are the maximum.

Preserving detail in landscapes should be done flexibly, but usually anthing above f8 should keep detail in mid to far distance. Including foreground detail, you will need to step down a bit, but I find I dont often visit f1/32

One ting though, all these number are relevent to 35mm size frames. Your H1 has a 6mm - 72 mm lens, and the minimum aperture size reflects this. You get F2.8-F8, even at relatively wide aperture ratios on this lens, you will get large Depth of Field for the equivelent 35mm focal length.

If you dig around on the net you can find some DoF calculators, for your 1/2.4 sensor.

 

[xolotl]

Once you've finished understanding hyper focal points have a look at this. A reason why small apertures arent always the best.

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm#

 

[Mister_Pister]

blimey so much to pay attention to..