Do I have a lens problem?
Dec 18, 2014 11:41:19 #
I shot this with my Sigma 150-500mm F/5.0-6.3 I posted another shot of this same deer in the Photo Critique Section. Someone said that I might need to check my lens because one side looked sharp while the other did not. I thought the right eye did not look as sharp because it is in shadow. Can anyone tell for sure what is going on here? Is it me or the lens or the situation?
I cropped this one close so it's easier to see. Here is another shot of the same deer within seconds of this shot that I posted in the Photo Critique Section.
http://www.uglyhedgehog.com/t-269000-1.html
I cropped this one close so it's easier to see. Here is another shot of the same deer within seconds of this shot that I posted in the Photo Critique Section.
http://www.uglyhedgehog.com/t-269000-1.html
Dec 18, 2014 11:55:58 #
donrent
Loc: Punta Gorda , Fl
Looks like a lighting shadow problem to me, not lens... Ck it out by taking a pic of something else , same distance and see..
Dec 18, 2014 11:59:19 #
donrent wrote:
Looks like a lighting shadow problem to me, not lens... Ck it out by taking a pic of something else , same distance and see..
Okay. Is it possible for the lens to have a problem at just certain focal lengths?
Dec 18, 2014 12:04:09 #
It is an optical illusion - the catchlight in the left eye is from a much broader light source (sky) than the sun in the right eye causing it to "look" less sharp .....I will also say that the lens appears to be front focused - for whatever reason .....
Dec 18, 2014 12:07:03 #
Nightski wrote:
Okay. Is it possible for the lens to have a problem at just certain focal lengths?
Very possible. I have just been to six reputable review sites and all report that it is sharp until you reach 400mm from there on it becomes increasingly less sharp.
Dec 18, 2014 12:10:31 #
Nightski wrote:
Okay. Is it possible for the lens to have a problem at just certain focal lengths?
in the critique section your deer's ears, eyes and nose were within the DOF range, some part of the head was in focus. none of the grass was focused.
In this shot none of the head can even pretend to be focused but the grass on this side of the head is starting to look pretty sharp.
Dec 18, 2014 12:10:42 #
Dec 18, 2014 12:32:54 #
Nightski wrote:
I do not know what front focussed is. Is it something that can be fixed?
In my opinion, the only way to be sure is to know what the camera was focused on.
The image may have the actual focus point embedded within it, so the right software would display what the camera was actually focused on.
In Lightroom I use a plugin called "showfocuspoints"
http://www.lightroomfocuspointsplugin.com/
For Canon & Nikon camera's it will show where the actual focus point was that was selected, and is a good tool to hone focusing skills.
It may be that the camera was actually focused on the grass in front of the deer instead of on the deer's eyes., which would make the lens appear front focused (aimed at the deer's head, but actually focuses some distance in front of the target)
If the issue is front or back focus, some cameras have a micro focus adjust that can fine tune the focusing for several lenses.
Dec 18, 2014 12:36:51 #
Dec 18, 2014 12:45:51 #
Nightski wrote:
Thank you, Mr. Gallagher.
we may be flogging a dead horse, at f 7.1 your camera/lens is diiffraction limited. you won't get a really sharp image no matter what you do.
Dec 18, 2014 12:55:18 #
oldtigger wrote:
we may be flogging a dead horse, at f 7.1 your camera/lens is diiffraction limited. you won't get a really sharp image no matter what you do.
You think I should take some test shots at f/8 to f/11?
Dec 18, 2014 12:59:44 #
Nightski wrote:
I do not know what front focussed is. Is it something that can be fixed?
Front focus (and back focus) is when you focus on a point but the focus ends up behind or in front of your focus point. There are simple tests to determine if that is a problem.
You can line up objects, such as camera batteries, at a diagonal, take a photo while focusing on the middle battery, at different focal lengths, and view them on your computer. You will then be able to see if in fact the object you focused on is sharp.
There are other means of doing this, just search on line and you will probably find a focus chart that you can print and use for this experiment too. I have used both batteries and the chart.
I'll add that there are ways of correcting that problem, provided your camera is capable of doing it. There is a setting on my cameras that I can make minor adjustments for each lens.
Dec 18, 2014 13:08:20 #
Wendy2 wrote:
Front focus (and back focus) is when you focus on ... (show quote)
This might sound like a silly question, but does this only happen in auto focus?
Dec 18, 2014 13:10:33 #
Nightski wrote:
You think I should take some test shots at f/8 to f/11?
that would only make it worse, you need to open up to 3 or 4.
You don't need to increase DOF, you need to increase sharpness.
Spend a few hours here and you will have a better understanding of why we all struggle with focus/DOF:
http://www.cambridgeincolour.com/forums/tags/focusing.htm
Dec 18, 2014 13:26:59 #
Nightski wrote:
This might sound like a silly question, but does this only happen in auto focus?
I don't think it is a silly question, but I have no idea. I always shoot in auto focus because I can't trust my eyes to get it right.
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