Hi,
I currently own a Canon 15-85 f/3.5-5.6 lens. I'm very pleased with the IQ in a good lighting/outdoors,
but i find it a little slow indoors or on a very cloudy day.
I wonder if the Sigma 17-50 f/2.8 will bring much difference to my shots.
Can anyone post some examples of shutter speed differences between the F numbers?
I suppose there won't be much difference between 2.8 and 3.5, but what about others?
Thanks
Going from f/5.6 to f/2.8 will allow you to use 4x shorter exposures. But you must remember the depth of field will also change too. If that isn't too important, then also consider a prime instead. For example, a 50mm f/1.4 at f/1.4 would need 16x less exposure time than f/5.6.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
[quote name='popo' timestamp='1332601641' post='16992']
Going from f/5.6 to f/2.8 will allow you to use 4x shorter exposures. But you must remember the depth of field will also change too. If that isn't too important, then also consider a prime instead. For example, a 50mm f/1.4 at f/1.4 would need 16x less exposure time than f/5.6.
[/quote]
Sure prime lens will perform best, but i'm shooting indoors mostly on family occasions, so using a prime while kids are running around won't be convenient. Therefore i'm looking for a zoom lens, just not sure if a f2.8 lens
will perform speedwise any noticeably better than my 3.5-5.6 lens and will reduce the number of blurred images.
For kids shooting you need something about 1/125 - 1/250 shutter speed (or even more sometimes). Put on your lens, set at f4.0 (for example), set highest usable ISO on you camera, and calculate, will f2.8 be enough. External flash could be an alternative.
A.
How do i calculate this? I am new to dslr photography...
If, for example, f4.0 shutter speed is 1/30, f2.8 will be 1/60 (in that particular environment). You can read about exposure on this site at "Technique" section, [url="http://www.cambridgeincolour.com/tutorials/camera-exposure.htm"]here[/url]or [url="http://www.dpreview.com/learn/?/Glossary/Exposure/Exposure_01.htm"]here.[/url]
A.
thanks for the info.
Would you say that 28mm f1.8 prime on my 600d could be the lens i need?
My intention is to shoot indoors and sometimes in dimmed light.
Trying to avoid using flash.
[quote name='iggykh' timestamp='1332825345' post='17084']
thanks for the info.
Would you say that 28mm f1.8 prime on my 600d could be the lens i need?
My intention is to shoot indoors and sometimes in dimmed light.
Trying to avoid using flash.
[/quote]
The 28mm f1.8 needs to be stopped down a bit to get good results, so it only gains you one stop at most. If 28mm is a focal length that suits your usage, it can be an option.
Of course, the Sigma 17-50mm f2.8 will already do a much better job than the 15-85mm. It will be 1 stop to 2 stops faster over the focal ramge they both cover, which means twice to 4 times as fast an exposure time.
How fast an exposure time you need depends on the shot. People talking, being together, eating, you can shoot with lower speeds than the mentioned 125th sec. It all depends on the movement of the people. And totally freezing all movement is not always wanted, as it makes images static.
So, it depends on the ISO setting m(and your 600D does very well with higher ISO settings, so ISO 800 or 1600 should be no problem), the situation, the effect you are after and a lot on your experience.
Just about any lens will be better though... an f2.8 zoom, a faster prime. The Sigma 30mm f1.4 HSM could be an alternative to the 28mm f1.8 you mentioned.
