One of the biggest challenges with macro photography is working with a limited depth of field or DOF. When I am shooting macro I am always trying to make sure the subject and elements in the frame appear sharp by adjusting the aperture and making sure the important elements in image fall on the plane of focus by adjusting my angle of view. But there is another important element that has a huge effect on DOF that most people don’t even know about, how a different sensor format can and will affect the depth of field in your image. Moving to a smaller sensor format at the same apparent magnification will give you lots more DOF to work with in your macro images.
Right about now most photographers even those that are at an advanced level will get a skeptical look on their faces and then proceed to tell me how wrong I am on this, but its true! Going from a full frame format to a DX format for example will give you 1-2 stops more DOF at a longer working distance.
For macro photography you should only be concerned with filling the frame and not a precise or exact magnification ratio. Instead you all you need to care about is fill the frame with a subject. With this in mind a smaller DX sensor will produce more apparent magnification than a full frame sensor since the object fills more of the frame at less magnification. In other words an object that fills the frame on a full frame sensor body at 1:1 magnification, will have much more working distance and Depth of Field when filling the frame with the same subject on a DX sensor body since you won’t need as much magnification and will be photographing from a farther distance.
Look at the following examples to see for yourself just how much more DOF there is in a smaller sensor format image vs a full frame image.