Sweet spot?

[Mickwreay]

Can anyone let me know if there are general sweet spots for the following lenses?

Canon 70-300 IS USM F4-5.6
Canon 50mm IS F1.4 almost new so not sure if it is a MK# etc.
Canon EFS 17-85 IS USM kit lens.

I get the low F stop etc, but is the a rule of thumb to aim for to get the sharpest results from the above?

Mick

 

[footman]

I can't comment on those individual lenses but I believe generally a sweet spot would be f8-f11.

 

[wazy15]

Generally it is when you tend to stop down by 2 to 3 times. a 50mm 1.4 might be sharp around f4 where as a f3.5 lens might be sharpis around 5.6 - 8. Each lens is different but it depends if you want bokeh or if you are limited to low light, in such cases you will need to default tothe lower f numbers to get the desired effect/light

 

[LikeBreathing]

I've been looking up the 70-300 recently and stumbled across these:

http://www.lenstip.com/8.4-Lens_review-Canon_EF_70-300_mm_f_4-5.6_IS_USM_Image_resolution.html
http://www.photozone.de/canon-eos/566-canon70300f456isapsc?start=1

Although it's worth carrying out your own tests as lenses may vary.

 

[squishy]

Yes, they have a sweet spot.

On a tripod, with a remote release and mirror lock up



But in general, lenses get sharper as you stop down, up till a point where diffraction kicks in and starts softening again.

The sweet spot is generally somewhere in between f/5.6 and f/11.

 

[Mickwreay]

Thanks for all the replies, the links are interesting LB.

I’m slowly starting to analyse my shots before taking now & am much more aware of speed versus focal length, ISO versus noise etc.

I’ve played with micro adjust, set up on tripod with remote release but I think it’s more that I need to step back a bit on the aperture to get the sweet spot of the lens. :shrug:

Mick