What is the problem with this picture ?

[stevestuff]

I am new to the world of Macro photography.

I have taken a about one hundred shots with this lens setup all

Canon lenses (Macro 180 mm f/3.5 and 1.4 II magnifier and a 25mm II

extender tube). I had the extender tube mounted on the camera body,

then the 1.4 magnifier, then the 180mm lens. Please look at this

picture of simple table salt placed on a piece of pastel paper.

http://www.photo.net/photo/2881669

Many of my shots like this one seem to have a small window (line) of

cleanness around the center of the shot, but if has a DOF on the top

and bottom of the shot (see the picture here). Can anyone please

explain to me why this might be occurring.

 

Thank in advance,

 

Steve<div></div>

[beauh44]

Hi Steve, I'm afraid I don't know what's wrong - it would be helpful to post a much smaller example though and more people will see it. It took a while to download it with a broadband connection. Anyhoo, just a thought, but since you're using three separate optics (lens, magnifier and extension tube) perhaps process of elimination might help. For example, is everything OK with just the Macro lens? Can you then add either the extender or magnifier without trouble? It *is* very strange - I can tell it will be an interesting shot once the problem's solved. Good luck!

[paul -]

<i> "have a small window (line) of cleanness around the center of the shot, but if has a DOF on the top and bottom of the shot"</i><p>That "small window (line) of cleanness around the center" <i>is</i> the DOF (Depth Of Field is what's <i>in </i>focus). The plane of focus is going to be only millimeters thick. Everything in front of, and in back of, this area is going to be out of focus.<p>Or isn't that what you are asking about?<p>Anywho, standard advice is to pick up a copy of John Shaw's <i>Close-Ups In Nature</i>. It's an excellent reference for macro photography.

[rich815]

With a macro lens, magnifier AND extention tube it looks like you have a very very very narrow DOF. And your image is what you get.

[paul -]

You shot that wide open at f/4 (it's in your photo's metadata). In macro, you need to close the aperture way down for more DOF.<p>The attached sample wasn't taken with the Canon lenses and tube you used (this is Vivitar 100mm macro on a Canon 10D), but shows the kind of difference stopping down can make.<div></div>

[joshua daniels]

As some of the other posters have suggested, you're operating with very shallow depth of field - an inherent challenge with macro photography. If you shoot with flash or can live with a long exposure, you can stop down considerably and get much better DOF. Another route is adding a tilt lens (Canon makes several, but the 90 with extension tubes would probably be the most appropriate) or something like the Combo or Zork Multi Focus System (see www.zoerk.com).

 

Joshua

[panos_voudouris]

Use http://members.rogers.com/jul.loke/jlcalc.html to calculate the DOF. You will see that focusing (say) at 0.5m at f/4 the DOF for your setup is <1mm. For f/22 it will be something like 5mm. If you move the focusing ring slowly you will be able to see the "window" moving across the scene. To get more DOF you will have to fully stop down and start using lower magnification ratios, i.e. remove the 1.4x or the 25mm tube and move further away from the scene.

[alan_olander1664878205]

You weren't focused on any of the salt grains in the photo you posted. Your focus point was just in front of the one grain of salt, and like others have said, your DOF is very narrow.

[mattb1]

The other thing that is going on with the photo has to do with the plane of focus. The plane of focus is parallel to your film/sensor at the distance you are focusing at. Every thing in that plane will be in focus. Only a shift lens or a view camera can alter that. What I do, is to try and imagine the plane of focus in relation to the subject as much as possible. In your shot, which looks to be from the side, the plane of focus is intersecting your subject in a line. Remember geometry, when two planes intersect the intersection forms a line. And the DOF will be in front and behind that line. If you were to take a photo of the same subject from overhead, the plane of focus would be much closer to more of your subject. And the DOF would include more of the image. However, that is not always possible, but is a good rule of thumb to consider it in your composition. It can give you more of the subject in the range of the DOF, or less of it if you want. Its not always wrong, it depends on the image...