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Originally Posted by meansizzler , I thought DSLR' made it easy, thought you twist the lense to change the focus but was then told that this only changes the zoom...  |
You've been misinformed, perhaps unwittingly.
You don't twist the lens though . it is the ring on it as the actual lens casing is rigid although its internal elements move
The lenses have 2 rings; one for zoom the other for focus.
Unless they are prime lenses with dont zoom ( because focal length is fixed,) they only have one ring for focus
All however all have very easy manual focus
As it happens DSLRs and compacts tend to AF differently..more on that below
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Also are the cameras not yet advanced enough to be fitted with lasers that you just point at the object your shooting at it will automatically calculate how far the object is and adjust the settings accordingly?, or is this what they call autofocus?, as I personally find that feature crap, when taking up close shots of PCB's it's no good, have to switch to manual
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The cameras do have accurate and quick auto focus in general employing Passive or active methods , which use slightly different means ( (infrared or reflection on sensor with distance computed by electronics( or both)to adjust the lens. AF does have limitations and poor contrast, reflections, user error make it not 100%, but c**p it is not . when it works ( which is most of the time,) it is fast and accurate
DSLRs employ the passive method as a rule
To shoot PCBs sounds like a Macro subject: that would be better done with Manual focus and a dedicated macro lens which allow you to get "up close and personal"
It is possible.. but not as easy with Non Macro lenses
The sigma 70- 300 does some sort of macro but I wouldn't use it if I had a lot to too
An example
PS: Sorry If Ive repeated you Dave..

Someone else might find it useful though