Comments made by Cisco - Page 6

Topics Created Topics Contributed Forum Comments Photo Comments

All Forum Comments

as the man says : keep the big one ! you may need it later

step-up rings +1 ^^

Comment by Cisco posted on Swap: CPL filter, 67mm for 62mm at 16/04/2011 - 16:16

pentaxian450 wrote:

Cisco wrote:
It can therefore instruct the lens to move directly to the correct position, without taking a second measurement or "hunting" around.

It doesn't exactly works like that. Since some lens have a longer focus throw than others, and since some lens screwdrive don't all use the same "drive ratio", the AF takes an "educated guess" to send the lens close to where the focus point should be for the AVERAGE lens, then it refines the focus in smaller steps.

That I wouldn't disagree with

The question is : does it check it's in focus at the completion of the final move ? or does it just assume it's in the right place ?? having calculated where it should be.

This is the bit I'm having trouble researching

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 16/04/2011 - 11:20

[quote:3496ace15f="Smeggypants"
Do you actually have a camera?[/quote]Several more than You ! I even make a living from it

I just like to know how they ACTUALLY work, NOT how someone THINKS they work !

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 16/04/2011 - 11:14

I simply wanted something Objective, rather than your Subjective findings

From your link :

It can therefore instruct the lens to move directly to the correct position, without taking a second measurement or "hunting" around.

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 20:42

Then why do we have a FF/BF problem ?? if it thinks it HAS achieved it ?

You still haven't explained how the system works, or provided links to justify your rash statements !?

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 18:35

So-called experts on the web !

Several times from different people !?

Explanation ?? or links ??

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 17:42

Just found this, I think it answers the question

AF cameras don't "keep adjusting" - they take one measurement of how far apart the images on the line sensors are, calculate how far the lens needs to shift, then shift that far. They don't then check to see if the image is in focus.

That makes it quite clear and explains why we need to adjust focus on a per lens basis

Tks for help !

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 17:07

But ALL those components are in the Camera body !! So how can the lens make any difference ?? It will be the same error for ALL lenses ?? No ?

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 15:46

but if it's out of focus at the Main sensor, then the info at the Focus sensor should also be out and an adjustment made !? as both light sources come through the same lens ?? is this not so ? I'm confused with this too !

links to more info required please

Comment by Cisco posted on Why do some lenses have front/back focus issues? at 15/04/2011 - 11:24

Arrived safely, tks Archie

Comment by Cisco posted on Four way Macro Rail Focusing Slider at 15/04/2011 - 11:17

Proudly supporting Pentax User

Cisco

All Forum Comments

All Forum Comments

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

Proudly supporting Pentax User