What is your standard prime?

Started 7 months ago | Discussions thread
Martin_99 Senior Member • Posts: 3,226
Re: What is your standard prime?

DutchMM wrote:

You ask why FF lenses could have faster AF than crop lenses. First of all, I don't know whether this is true. Thus far, all my e-mount lenses are crop.

It depends on each lens design and used AF motor. No relation on lens format.

In general FF lenses have advantage of higher price point, so better AF motor is easier to implemented from economic point of view, but on the other side FF lenses have heavier glass which is harder to move quickly...

That said, I have a theory that the faster the lens, the faster the AF. Because the AF systems in (at least) Sony bodies perform the AF with the aperture wide open.

Are you sure?

So faster lens = more light = faster focus.

I think that this is only part of the truth. When camera have more light it maybe process the focus faster, but AF motor have to do the hard work. So if lens AF motor is slow, no amount of light will help.

Although both FF and crop lenses project the same image on a crop sensor, the FF lenses have to let in enough light to avoid severe vignetting in the corners of an FF sensor. Hence most of the FF lens makers are hard chargers for fast lenses. I except Sigma from this remark, since there is a triad of F1.4 lenses for crop sensors. But has anyone ever offered you a crop lens with a max aperture of 1.2, leave alone 0.95?

Not understand this part of post. Nevertheless Fuji have 56f1.2 and 50f1 lenses. Because they are apsc specialist and care about this format. Sony's main format is FF.

 Martin_99's gear list:Martin_99's gear list
Sony a6400 Sony Carl Zeiss Sonnar T* E 24mm F1.8 ZA Sony E 18-135mm F3.5-5.6 OSS Sigma 56mm F1.4 DC DN | C (X-mount) Sony E 70-350mm F4.5-6.3 G OSS +2 more
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