Lens/Aperture question

[Bolton]

I have a question about light and aperture with different speed lens'. Does a 2.8 lens let in more light at say F5.6 than a F4 lens at the same F5.6 setting?? Or is the light entry the same at 5.6 on both lens' no matter how wide the lens can get? Thx

 

[strebble]

same same.... as long as the lens is calibrated the same

 

[Steve]

Yup, F/5.6 is F/5.6. Same light regardless (technically there can be very slight variances, but it's essentially the same).

 

[Bolton]

Thank you!!

 

[Pistnbroke]

The lens will focus at the max aperture so the f2.8 lens will find it easier to focus in low light than an F4. only stops down to F8 to take the picture

 

[Bolton]

The lens will focus at the max aperture so the f2.8 lens will find it easier to focus in low light than an F4. only stops down to F8 to take the picture

Something else I didn't know...thank you!!!

 

[Yezdi]

f5.6 is f5.6 on both lenses.

 

[DRwyoming]

Something else I didn't know...thank you!!!

Yeah, @Pistnbroke 's point is worth remembering as it means a few things:

- The faster glass gives you brighter viewfinder images even when both lenses are stopped down
- The faster glass helps your AF system regardless of current aperture selection
- Since the image you see through a DSLR's viewfinder is the wide open aperture, you're not really seeing the Depth Of Field of the final image unless you're shooting at the wide open aperture. So when shooting with a DSLR and wanting more DOF for something like a group shot or a scenic you can: just stop down a bit and hope, check a DOF calculator for static shots, use Live View which shows the stopped down DOF or use DOF Preview available on many modern cameras to see the stopped down image through the optical viewfinder.