i second that...

1. A300 and brothers, doesnt has a AF illuminator, they use the pop up as AF assist.
2. attach ur flash, to use the build in AF illuminator. your tamron Will Not Hunt Anymore.

3. F2.8 advantage is not before shutter release, the advantage is During shuttle release. meaning, with 16105, F5.6, shooting the same subject with natural light, gives u 1/5ss, while the F2.8 give u a decent 1/25ss which prompt to less motionblur. F2.8 is like bumping iso to 1600 on F5.6 with less noise.

4. tammy 1750, well, Practically, its for indoor use. not outdoor with wide ground. even i rate 55200 is better then 16-105 for outdoor street shooting. (my opinion, but many prefer 16105)

well if not then go straight for

1680CZ only....i have not really seen how good a CZ is..............time to go test test

i just got my cz1680 and im really please with the result... is so much sharper compare to my previous kit lens and also the minolta 28-85...

the advantage of having a brighter aperture does help before shutter release la..it helps in AF...
f/2.8 focuses faster than f/3.5 ....because it allows more light

if im not mistaken, ur lens will open at its max aperture (brightest, f/2.8 for 1750 and /f/3.5 for 16105) before the shutter...

correct me if im wrong....

This post has been edited by Sp00kY: Nov 3 2009, 10:44 PM

u are kinda wrong and right at the same time, i am assuming as, not everyone is using A700 with F2.8 AF sensor. if u are A700, yes it helps the focusing more accurate, not faster, not improve in hunt*(hunt as it will still miss under low light + AF illuminator OFF) but A700 Have AF illuminator for AF assist, thus, well, A700 is like having the right key for night shooting, AF assist +F2.8 sensor.

well, u try this, take ur 1870 kit lens, wide, set to 3.5 and shuttle release, and pls watch as they turn the apperture down to F3.5 to snap, yes, turn down. meaning at normal, ur apperture is not at 3.5, it wwwiiiiddeerrrrr try it with 50mm F1.4, when wide open, it is not F1.4.... i think it's 1.2 ehem L lens?!?!!?

assuming not everyone owns A700, and use A300 as key model, and shooting in natural light (no flash, no external flash attach.)
like i say, not before shutter release. it does not help at all in AF. what i mean during is that, it is resposible for the shutter speed gain VS F5.6. the one that give the AI decision to release the at what shuttle speed.. shutter speed gain is a major difference.

test 16105, at 50mm F5.6 shoot subject 10 meter away,

Vs

test 1750, at 50mm F2.8 shoot subject 10 meter away...

those who owns tammy would really really know the answer and differences.

and even better is, when, very very very malang, ur flash battery dead. F2.8 iso 800/1600 on A300 still can let u continue ur wedding/event job compare to a F5.6

This post has been edited by ieR: Nov 3 2009, 10:57 PM

read this article.... which pretty explains how Autofocus can benefit from f/2.8 lenses

http://community.the-digital-picture.com/forums/t/2012.aspx

ronnie, does that apply to sony AF sensor?


*edit: if u say, F2.8 and compare to a AF illuminator? i'd say the illuminator helps more.

btw, the A550 has much improved sensor, it can AF better in darker area vs A300 (as both are without AF illuminator)

This post has been edited by ieR: Nov 3 2009, 11:07 PM

i think is some kind of masking technique in the photoshop, nt sure if im correct..=D

the discussion is on Canon... but theory wise it explains the concept of F2.8 AF sensors

yea, but, each sony model has diff set of sensor design. A700 has F2.8+AF illuminator. A300 has so called F5.6 sensor + pop up as AF assist, and when u popup for assist, it will sure fire when u release. and many discussion over and over, A300 doesnt not benefit from F2.8

and summore our sony sensor design, was passing through a mirror (that mirror the image upwards into the OVF) onto another mirror behind the main mirror, mirroring down into the bottom, where the sensor is locates, which is hell of dark area. but first, the amount of light going into the sensor area, is already limited by the tiny hold of the main mirror. me and my bad english... can i write in korean? its easier for me to explain that way...

This post has been edited by ieR: Nov 3 2009, 11:17 PM

From the explanation above, it mention that Special AF system become active when using 2.8 or faster lens but do our a2xx-a3xx have that? I can't see af faster by much from 50 1.8 compare to kit lens.

Anyone here using Phottix BG+battery? How is it? Thinking to get it because it is much cheaper compare to Sony one but I scare to spoil my camera pulak

Which models have F2.8 sensors ?
Which models have F5.6 sensors ?

dear ronnie, only A700, 850 and 900 has the dedicated F2.8 sensor while the others are using common sensor, which wont benefit from F2.8

A700 will focus faster than A200 with the same lens with f/2.8
Is the above true?

TRUE


hehehehe, even 550 doesnt have the F2.8 sensor, but with the new design of AF system, they are on par with A700 at night time, but still wont be as accurate as a dedecate F2.8 sensor

Faster, is lens depending, how long the focus screw, build in SAM or SSM or manual (manual is u never get to focus on ur subject.... )

it's due to F2.8 as we know, the DOF is shallow, thus, accuracy is another issue VS able to hunt or not.

on A200/300, it may able to hunt at F2.8, tit teett... but,... the next question is, is it accurate? those with A200/300 with 1750 F2.8, will sure tell, 50% accurate, 50% not accurate. but try attack ur flash gun F42 and F58, with built in AF illuminator, the accuracy increase slighty, or much better.

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Added on November 3, 2009, 11:48 pm

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Added on November 3, 2009, 11:50 pmand worst part is, the main mirror only allows like 30% of light through only, so imagine u shoot at low light, how suffering is the sensor trying to get a decent focus?

This post has been edited by ieR: Nov 3 2009, 11:50 PM

this is what i understand :
"A faster lens (wider max aperture) allows more light into the camera and gives the AF system more light to work with, so a faster lens will allow better AF performance when light levels get low enough to start effecting the AF speed"
quoted from someone:)

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Added on November 3, 2009, 11:59 pman f2.8 lens allows twice the light as an f4, and an f4 allows twice that of an f5.6

This post has been edited by Sp00kY: Nov 3 2009, 11:59 PM

Yea..by using Flash AF illuminator..u wont have problem focusing.

sp00ky..i believe kysham said tht before.

This post has been edited by AlphaBeta: Nov 4 2009, 12:05 AM

Attachhhhhhhhh LOL hahahaahahahahahaha

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Added on November 4, 2009, 12:07 amalso the reason why we keep insisting anyone who is thinking about getting 3rd party flash, Get F42 or F58, they have better AI, WL flash, AF Illuminator.

This post has been edited by ieR: Nov 4 2009, 12:07 AM

ieR, have ur 1750 ever hunted in lowlight although f58 is attacked?