Specifically for the discussion of the A-mount DSLR range
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Greg, the KM/Tamron and the Sony versions of 28-75 have very different mechanical body design. Hence the weight difference.
And then Sigma and Tamron used to have the same exact lens designs in non-motorized versions for Sony/Pentax; no weight difference from the motor presence was ever reported.
[quote="Greg Beetham"][quote="pakodominguez"]I had the chance to use for a month, side by side, the KM 28-75 f2.8 and the SAM 28-75 f2.8 -optically the very same lens. The SAM focused faster AND more accurate than the KM version -the build quality on this lens is much better than what we can find on the "easy choice" lenses, I don't know if the SAM on it is also "much better" or not.[/quote]
The build quality of the KM28-75 looks to be of a very high standard to me, the fits and tolerances are very neat and smooth, and even if it is plastic as you say one would be hard pressed to realize it. In any case the question was, is a SAM version of a lens bigger and heavier than the screw drive version, and I believe that I've shown that it is, in any case I still say we didn't need SAM lenses in the first place, SSM yes SAM no.
Greg[/quote]
It seams that you have not had the Sony 28-75 f2.8 in your hands. It is built like the Zeiss lenses, while the KM ain't bad, but it doesn't feel as "professional" grade lens. That (and not the SAM that you dislike) is what make the Sony a 800$ lens.
I do respect the fact that you don't want Video DSRLs and the fact that you find SAM useless -but the example you are providing is not accurate. Nor what someone else said about SAM lenses been noissier than screw drive lenses: I did try side by side the Zeiss 85 f1.4 against the SAM 85 f2.8 and the Zeiss doesn't AF faster and sound like a tractor.
I think we are in the middle of a roundabout where Sony is still deciding about DSRL and SLT -every one somehow related with Sony I spoke with in the last 6 months is not sure of what the next 7 series camera will be SLT only or a DSRL sister will hit the shelves at the same time.
In any case, I don't think we will see any other pure DSRL-non-video camera. From any maker.
OneGuyKs wrote:
Because their PDAF AF system is not compatible with EVF? Didn't I say that before?
Boy ah say boy, (somthings got me by the leg) d-o-g spells chicken...I don't think any of those pros are concerned that their PDAF is not compatible with an EVF they don't have.
Greg
OneGuyKs wrote:
Because their PDAF AF system is not compatible with EVF? Didn't I say that before?
Boy ah say boy, (somthings got me by the leg) d-o-g spells chicken...I don't think any of those pros are concerned that their PDAF is not compatible with an EVF they don't have.
Greg
You are again "speaking" for all the pros. You asked why 1D and 3D use OVF finder, and I answered you. The OVF is a BYPRODUCT of pdaf AF system. They NEED (they are forced to) have OVF with PDAF since the mirror is required to split the light towards AF sensor.
Olympics that you are watching on TV are shot with camcorders with ZERO OVF because these camcorders don't have similar limitation that REQUIRES them to have OVF.
OneGuyKs wrote:
You are again "speaking" for all the pros. You asked why 1D and 3D use OVF finder, and I answered you. The OVF is a BYPRODUCT of pdaf AF system. They NEED (they are forced to) have OVF with PDAF since the mirror is required to split the light towards AF sensor.
Olympics that you are watching on TV are shot with camcorders with ZERO OVF because these camcorders don't have similar limitation that REQUIRES them to have OVF.
I didn't ask why the 1D and D3 use OVF's I was telling you that they do, and the OVF isn't a by-product of PDAF, the OVF came first then along came PDAF a long time later.
I don't care that videocams use EVF's they are welcome to them.
Greg
Greg Beetham "You might have actually got one right, but anyway who cares? why bother putting CDAF in the camera at all?"
I got more than just "one" right.
Why CDAF?
CDAF can be 100% accurate with no back/front focus issue and 100% perfect focus. This can be useful on tripod work where speed isn't needed.
In future models someday, CDAF might be used to calibrate lenses that are off and require micro focus adjustments. Sony can add a feature so that the camera can use CDAF to auto calibrate lenses that have front/back focus issues.
OneGuyKs wrote:
I didn't ask why the 1D and D3 use OVF's I was telling you that they do, and the OVF isn't a by-product of PDAF, the OVF came first then along came PDAF a long time later..
Greg
OVF are 100% a byproduct of PDAF system and not the other way around. This is especially true in digital age where all current DSLRs are stuck with OVF because PDAF requires a mirror to split the light.
This is not a "plus". It's a negative (and at best, to be charitable, a byproduct of AF design).
agorabasta, probably when they can make an EVF/OVF that doesn't use any power, has all the plus attributes of the an EVF and the instant transmission of an 100% OVF I'll be happy...maybe, but in the meantime it's fun stirring the pot.
Greg
CDAF can be 100% accurate with no back/front focus issue and 100% perfect focus.
That's simply not true. CDAF looks for a maximum contrast over an area analysed. If two high-contrast objects at slightly different distances fall into that area, the CDAF would focus somewhere in between - that's a serious limitation that can be overcome only with serious computing power.