Lens Sweet Spot and Censor Size

[AlfyB]

I was reading an article today talking about lenses having an aperture/sharpness relationship with sharpness often being maximised around f8-11.

That's fine but it then went on to say that people using crop sensor cameras might want to stick with f16 when maximising DOF to keep images sharp but on FF sensors f22 us more likely to be ok.

Have I misunderstood? If not, why would sensor size would make a difference to the sharpness?

 

[skiwhiz]

will be interested to see what people have to say, have been playing with a new lens to try and find the sweet spot but have not managed yet.

 

[jpw]

I was reading an article today talking about lenses having an aperture/sharpness relationship with sharpness often being maximised around f8-11.

That's fine but it then went on to say that people using crop sensor cameras might want to stick with f16 when maximising DOF to keep images sharp but on FF sensors f22 us more likely to be ok.

Have I misunderstood? If not, why would sensor size would make a difference to the sharpness?

Pixels are usually bigger on FF sensors.

 

[Tricky01]

The point is explained (along with the other major differences) here

You do really need to understand all the differences as quite a few overlap. Essentially the larger the sensor, the greater the angle between the lens and the sensor. This results in an effectively shorter depth of focus.

Taken from the link:

...if one wanted to reproduce the same perspective and depth of field on a full frame sensor as that attained using a 10 mm lens at f/11 on a camera with a 1.6X crop factor, one would need to use a 16 mm lens and an aperture of roughly f/18. Alternatively, if one used a 50 mm f/1.4 lens on a full frame sensor, this would produce a depth of field so shallow it would require an aperture of 0.9 on a camera with a 1.6X crop factor — not possible with consumer lenses!

It's all very interesting, and actually very well explained by john Greengo in his training sessions on CreativeLive.com. I know I bang on about these a lot but I am only an advocate because it was such a good series - I'm not getting paid in cash or other to plug it!

 

[nano]

The might also be talking about diffraction where the effects are lessened on a larger sensor. Hence why f64 is fine on large format gear.

 

[HoppyUK]

The might also be talking about diffraction where the effects are lessened on a larger sensor. Hence why f64 is fine on large format gear.

Yes, it's simply a diffraction effect which I think the OP is referring to. All things being equal, with the same lens on FF and crop format, diffraction will kick in at about one stop higher on full frame, due to the lesser degree of magnification required from the larger sensor to achieve the same size output. The calculation is f/number x crop factor.

There is a recent thread on it, started by EdBray.

 

[AlfyB]

The point is explained (along with the other major differences) here

Thanks for the link I just had a read through and it has a lot of useful info. Think it's going to need to be read a few times before I start to properly understand though

Thanks for the comments everyone. Time to start understanding what diffraction is all about.