Nikon 50mm f/1.4 AF-S G review

[David Kilpatrick]

No, the secondary mirror would have to be one inch wide or more and the sensor would need to be larger than the CCD/CMOS- f/2.8 sensors are already BIG items. That's why you can not have 15 f/2.8 sensors and why all the sensors in the Nikon D3 (etc) are only f/5.6 - they could not fit lots of f/2.8 ones.

David

[youpii]

What can they do to improve focus accuracy then ?

[David Kilpatrick]

Improve the spatial frequency detection of the sensors behind the AF prismatic lens system.

David

[youpii]

Improve the spatial frequency detection of the sensors behind the AF prismatic lens system.

I didn't really understand that
I somehow understand how AF works from this page:
http://www.nikon.com/about/technology/c ... /index.htm" onclick="window.open(this.href);return false;
Do you mean giving more space between the two AF images?

Yes, Nikon D3x has
• 51 focus points
• 15 cross-type sensors (F5.6)
Did you notice less AF accuracy when using F1.4 lenses with the D3x?

And Canon EOS-1Ds Mark III has
• 45-point TTL CMOS sensor
• 19 cross-type for F2.8 or faster lens
19 sounds like a lot but the Mark IIIs had a lot of firmware & hardware updates for AF, so I guess it does not work so well.

[David Kilpatrick]

Improve the spatial frequency detection of the sensors behind the AF prismatic lens system.

I didn't really understand that
I somehow understand how AF works from this page:
http://www.nikon.com/about/technology/c ... /index.htm" onclick="window.open(this.href);return false;
Do you mean giving more space between the two AF images?[/quote}

That is what f/2.8 sensors do - I meant, use a higher resolution imager in the sensor.

Yes, Nikon D3x has
• 51 focus points
• 15 cross-type sensors (F5.6)
Did you notice less AF accuracy when using F1.4 lenses with the D3x?

The Nikon focus is poor. It simply can not focus at all on many subjects in low light, and it is very erratic even in good light. Nikon users will deny this till they go blue in the face, and say it must be user error etc etc. Not so. It simply does not focus with the same ease and accuracy on low contrast subjects, or in low light, as current pro Canons or the Sony A700 and A900. Using an f/1.4 lens makes no difference, it's no more accurate than using an f/5.6 lens.

And Canon EOS-1Ds Mark III has
• 45-point TTL CMOS sensor
• 19 cross-type for F2.8 or faster lens
19 sounds like a lot but the Mark IIIs had a lot of firmware & hardware updates for AF, so I guess it does not work so well.

The 45 point is metering not AF. I don't know how Canon fits 19 cross type AF f/2.8 sensors in, but they use more of the full frame area on the 1Ds MkIII than Nikon use on the D3/700 series (or Sony use on the A900 where all of the AF is crammed into the centre). My guess is that the optics are compound, like the Nikon (one big AF lens if effect with a load of sensors behind it), I have never taken one apart or asked.

Just be thankful the A900, in particular, has about the most accurate central focus sensor combo ever designed. I don't care about any of the wide area focus modes or anything except AF-S, lock and hold, centre sensor. I want best possible accuracy with that and the A900 delivers in even the worst imaginable conditions - last week I was shooting by moonlight with an f/5.6 wide angle (12-24mm Sigma) and it could still lock focus accurately by the full moon.

David

[InTheSky]

I can second on that , that the A900 focus system is able to focus at very low light condition.

When I have tried the 500mm f/8.0, it was usual to forget that the best input of light for this lens is F/8.0 with how many time the camera was focusing correctly on almost any subject.