Go to a  "printer friendly" view of this message which allow an easy print Printer-friendly copy Go to the page which allows you to send this topic link and a message to a friend Email this topic to a friend
Forums Lobby GET TO KNOW YOUR CAMERA & MASTER IT Nikon D5300/D5200/D5100/D5000/D3300/D3200/D3100/D3000 (Public) topic #6560
View in linear mode

Subject: "RE: Where is the focus?" Previous topic | Next topic
Skyco Silver Member Nikonian since 12th Mar 2012Sat 25-Aug-12 11:51 PM
121 posts Share on Facebook Share on Twitter Share on Linkedin    Click to send email to this author Click to send private message to this authorClick to view this author's profile
#11. "RE: Where is the focus?"
In response to In response to 10


Roanoke Island, US
          

>But why? As I understand it, the light comes in the lens and
>most of it is reflected up to the eyepiece. The rest of it,
>since the mirror lets some of the light through, goes to
>anoter mirror behind the main mirro and at a 90 degree angle
>and is reflected down to the focusing sensor on the floor of
>the camera. When the picture if focused, the sensor tells the
>lens to stop focusing. If the distance the light travels
>between the back of the lens and the focusing sensor is not
>exactly the same as the distance it travels between the back
>of the lense and the imaging sensor, the focus will be wrong.
>If there is something wrong, how is changing the lens going to
>affect this. If the focus is right, how is a different lens
>going to mess it up? What does the lens have to do with any
>difference between these two distances?

I think that we are talking about two different things, image quality of the lens and Auto Focus.

IMAGE QUALITY: I think its the quality of the lens glass - placement of the lens elements I don't know - Like you said it sucks. We would expect more from an $800 lens. It doesn't affect the focus of the camera, its just that at some (maybe many) focal lengths and distances the 18-200 lens is not very sharp (your question "Where is the focus"). There are quite a few photos that I took with that lens which I have been very disappointed with and kept thinking it was me or the camera.

AUTO FOCUS and what may have pulled your camera's auto focus: Items of high contrast near your intended subject of focus can influence your camera's auto focus. In your first photo of the flower from your earlier post, I think what happened there was that the brighter light and difference in contrast pulled the focus to the flower pedals behind the part of the flower you intended to focus on.

Sometimes manual focus works better when there are items near your intended target that have greater contrast, or moving to get a darker background. Earlier this summer I was photographing day lilies and to get the front for most stamen and the others behind in focus, I had to use manual focus because the camera kept shifting focus to the stamens that were closer into the flower (more contrast) and I wanted to keep a wider aperture to keep the background out of focus.

Looking at that flower and the petals "in focus" in your earlier photo the 18-200 still did not produce a crisp fine image of the detail on those pedals. I am amazed at the detail that the 18-55 and 55-200 "kit lenses" show, and bummed that I spent $800 on a lens that I have been more often than not disappointed in.

Well Wishes,

Ken

Visit my Nikonians gallery.



http://www.flickr.com/photos/skyco_g/

"Humans don't rise to the occasion. Instead, we fall to our level of training and experience". Archilochus, a Greek soldier and poet.
The best photo advice I ever received was at a John Shaw workshop. "... Practice your craft... ... Pixels are free...Practice... experiment with your camera".

  

Alert Printer-friendly copy | Reply | Reply with quote

A general, generic topicWhere is the focus? [View all] , grnzbra Silver Member, Tue 21-Aug-12 12:22 PM
 
Subject Author Message Date ID
Reply message RE: Where is the focus?
JosephK Silver Member
21st Aug 2012
1
Reply message RE: Where is the focus?
gkaiseril Gold Member
21st Aug 2012
2
Reply message RE: Where is the focus?
grnzbra Silver Member
23rd Aug 2012
3
     Reply message RE: Where is the focus?
gkaiseril Gold Member
23rd Aug 2012
4
     Reply message RE: Where is the focus?
grnzbra Silver Member
23rd Aug 2012
5
          Reply message RE: Where is the focus?
Skyco Silver Member
24th Aug 2012
6
          Reply message RE: Where is the focus?
grnzbra Silver Member
25th Aug 2012
10
               Reply message RE: Where is the focus?
Skyco Silver Member
25th Aug 2012
11
          Reply message RE: Where is the focus?
pjonesCET Gold Member
24th Aug 2012
8
          Reply message RE: Where is the focus?
gkaiseril Gold Member
24th Aug 2012
9
     Reply message RE: Where is the focus?
pjonesCET Gold Member
24th Aug 2012
7
          Reply message RE: Where is the focus?
Stonecherub Silver Member
26th Aug 2012
12
               Reply message RE: Where is the focus?
gkaiseril Gold Member
26th Aug 2012
13
                    Reply message RE: Where is the focus?
grnzbra Silver Member
26th Aug 2012
14

Forums Lobby GET TO KNOW YOUR CAMERA & MASTER IT Nikon D5300/D5200/D5100/D5000/D3300/D3200/D3100/D3000 (Public) topic #6560 Previous topic | Next topic


Take the Nikonians Tour and learn more about being a Nikonian Wiki /FAQ /Help Listen to our MP3 photography radio channels Find anything on Nikon and imaging technology - fast!

Copyright © Nikonians 2000, 2014
All Rights Reserved

Nikonians®, NikoScope® and NikoniansAcademy™ are trademarks owned by Nikonians.org.
Nikon®, Nikonos® and Nikkor® are registered trademarks of Nikon Corporation.