which lens to buy?

[David Kilpatrick]

Just to emphasise the point about the extremely inconsistent focus and sharpness of the 16-80mm as used by me last week in what should have been perfect conditions (clear sunshine in Tenerife), this is a 100% clip of a shot taken using the Sigma 8-16mm at 8mm, set to f/6.3 - an aperture which also produced much sharper images than f/8 or f/11 on the A77 with the 16-80mm.

f6p3-8mm-100pc.jpg (47.32 KiB) Viewed 4775 times

The A77 is capable of amazingly fine detailed resolution. I suspect my 16-80mm is tending to focusing too close at longer focal lengths on distant subjects, but plenty of shots show that it is focusing perfectly at 16mm wide open so programming in a correction becomes a difficult decision. What focal length, what aperture, what focus distance for the one-setting correction?

David

[stevecim]

This has been posted at Dyxum... would be interesting if , A. it's true, B. helps with the 16-80CZ
----------------------------------------------
Just in from my supplier:

A77 1.04 firmware up date will be available from the Sony Asia website on Tuesday see info below.

1. Target date of posting the download on Sony Asia website is 14:00 SG Time (GMT + 8hrs) on Tuesday, 29 Nov 2011.
SLT-A77V Firmware Upgrade

Ver.1.04 (Microsoft Windows)
http://www.sony-asia.com/support/download/478891

2. Additional Features / Improvements
• Lens compensation function is extended to the following lenses
 SAL1680Z
 SAL16105
• Functional improvement
 Improvement of responses
 Improvement of picture quality
 Improvement of usability

[agorabasta]

Which it can't do, and the lens is perfectly accurate on other cameras, so I don't think that hypothesis works.

Actually, it's still possible if the aperture somehow overshoots, which is possible if it's driven too fast due to the design of mechanical aperture control in the a-mount. The camera simply pushes the aperture lever and doesn't pull it back; if the push is too fast, the inertia may carry the system farther than intended and the spring in the lens has not enough time to pull that overshoot back.

So Greg's hypothesis may have place in reality, too...

[agorabasta]

The official 1.04 posted today is the same bit-exact file as the earlier leaked 1.04 from the Chinese link.

Means you may forget any real "Improvement of picture quality".

[Dr. Harout]

I guess it should be a firmware with a change in the second or first digit to see any real improvement (as I have read). This is just a bug fix, they say.
Don't ask me, I have no ideas on such matters.
BTW, thanks for the update link. I just did it.

[Greg Beetham]

David I’m just saying we don’t know what these guys have been able to accomplish internally, the camera processes happen at close to the speed of light. If one stops and thinks about it, a shutter time of 1/60sec is a fast motion on our human terms but a whole epoch in camera time scales, time enough for millions of operations. They might be doing exposure adjusting ‘on the fly,’ sensor flash gain during the exposure, or dark frame mixing to fix overexposure, all sorts of stuff.
I remember telling you about the time I was playing around with my two Metz 45’s (a Metz 45 is a much more powerful flash than an F56 or an F58, it has a GN of 45 @ 21 degrees coverage, an F56 @ 21 degrees is probably only about GN30 if it’s lucky) with the A700; I still swear that the A700 in A-mode was internally adjusting exposure ‘on the fly’ DURING the exposure despite having no direct control over the output of the flashes that I set at different ISO’s and f-stops across a big range and left the camera with it’s original ISO and f-stop. The camera appeared to be able too accommodate over exposure to at least two stops and make the results look the same, or very similar, it was still doing some compensating at 5 stops but it was loosing the battle there. So I remain suspicious of just what might be going on now inside a camera like the A77.
Thanks agorabasta, I just have my suspicions about the death of the on lens f-stop settings, with those they were set in stone (outside of a sticky diaphragm), if you set an aperture on the lens that’s what you got due to the sector tab on the back of the lens, no possibility of over travel. But now with f-stops set on and controlled by the camera the camera has to know where to set the camera quadrant for f11 for every lens and that position is not in the same position for every lens and it gets very complex for variable aperture zooms, in effect the camera has to have the T-scale for every lens that is going to be put on it. That’s why I suspect that digital cameras do compensation ‘on the fly’ because the absolute mechanics are no longer there between the actual lens diaphragm and the camera.
Greg

[stevecim]

Picked up the Sigma 18-250mm OS HSM today, not bad, ordered it late friday and they tried to deliver it Monday afternoon but no one way home at the time ( from Hong kong to Oz over the weekend)

was dark by the time I got home, so here are some samples shots, taken in the study.
first shot 250mm f6.3 (flash) + 100% crop





next shot 180mm f6.3 (flash) + 100% crop





very happy with the sharpness and colours so far and sharpness should get better stopped down a little more

[Greg Beetham]

Looks very good stevecim. Maybe a teensy bit overexposing (on my screen) but very sharp, good lens by the looks.
Greg
btw what caused all those scratches on the poor old Toledo?

[agorabasta]

In my not so humble opinion, that Sigma supezoom is the second best ever created. The very best is the SEL 18-200, but that can't fit

[stevecim]

Lots of use since 1984

[agorabasta]

Lots of use since 1984

Using E-mount since 1984?

Those metal rulers get a lot of tiny scratches almost immediately, they really show at close look.

[Greg Beetham]

I think those Toledo's are very fine instruments, I have the full set and keep em in the original plastic sleeves when not in use, I'll have to check now agorabasta to see if I have any scratches, I'll be mortified if there are.
Greg

[agorabasta]

Greg, and exactly those plastic sleeves are one the main sources of scratches, as they rub accumulated hard dust particles into the metal
But they look good with those scars - means they serve the purpose.

[David Kilpatrick]

Which it can't do, and the lens is perfectly accurate on other cameras, so I don't think that hypothesis works.

Actually, it's still possible if the aperture somehow overshoots, which is possible if it's driven too fast due to the design of mechanical aperture control in the a-mount. The camera simply pushes the aperture lever and doesn't pull it back; if the push is too fast, the inertia may carry the system farther than intended and the spring in the lens has not enough time to pull that overshoot back.

So Greg's hypothesis may have place in reality, too...

The aperture might do that but the camera can not post-correct for an over or underexposed image, which is what Greg suggests. We all know that lens apertures can vary and indeed do vary from shot to shot, even with the most precise FAD mechanisms. You may remember the XD-7, which introduced real-time monitoring of the TTL exposure as the aperture closed, and was able to correct for complete aperture failure - it would produce a correct exposure even if the aperture jammed open or shut down to its minimum. That function continued with the XD models but not with the XG, and was lost in the X-700/500, and never reintroduced for Alpha - possibly because they reckoned they had a better iris mechanism.

Sony has never claimed such a function for the Alpha 77/65, and indeed if it existed, it would remove your ability to lock exposure with first pressure on the shutter button. The exposure is set before the aperture closes, and frozen. There's no self-correcting process. It is easy enough to confirm this.

David

[Greg Beetham]

Well ok, reluctantly the post adjusting is out until proven otherwise, but what about exposure compensating DURING the exposure, by boosting the gain a tad or something like that.
Btw I still have my X-700 handbook (in pristine condition) and I’m fairly sure that camera can adjust the exposure during the exposure as long as the MD lock button is engaged (MD lens needed)….I’ll have to dig it out and check sometime.
Greg