as i understand it, the shorter the focal length of your macro lens, the closer you must be to your target:
What the Focal Length is Going On Here?
So, why invest in a 180/3.5 lens if it will only achieve the same level of magnification at closest focus as a 60/2.8? The simple answer is distance from the subject. When shooting a diamond ring, for example, it is far easier to do creative lighting when you are two feet from the subject (as you would be with a 180/3.5) versus the nine inches you would have with a 60/2.8 at the same 1:1 magnification. -
Which Focal Length Macro Lens Is Best For You? | Expert photography blogs, tip, techniques, camera reviews - Adorama Learning Center
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For many situations, you will probably want a comfortable working distance, nothing too close or too far from your subject. This explains why the short telephoto macro lenses are among the most popular. The 90-105mm range is filled with options and provides a great balance of distance and performance without making the lens itself unwieldy or intimidating. In some instances, such as when shooting easily startled insects or when distance is desired, there are even longer options available. Going up to the 180mm and 200mm range, you will find some serviceable telephotos to get you close without requiring you to be right on top of your subject. Additionally, with these lenses you will have space to use larger lighting equipment without getting in the way of the light. -
How to Pick a Focal Length for Macro Photography | B&H Explora
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Minimum focus and working distance
The “minimum focusing distance” lens specification can be confusing. Minimum focusing distance is measured from the subject to the rear focal point of the lens, which is at the image sensor plane in the camera body. The term “working distance” is used to describe the distance between the subject and the front element of the lens.
If a lens is specified as having a 0.2 m (20 cm) minimum focusing distance, for example, depending on the thickness of the camera body and the length of the lens, you might only have a few centimeters of working distance when focused at the minimum focusing distance in order to take a 1:1 macro shot. Being that close to your subject can make lighting difficult (special macro flashes and ring lights are available to overcome this type of lighting problem), focusing can be difficult if the subject or camera moves even slightly, and you’re likely to scare away living subjects at such close distances. If any of those problems occur, you need to choose a macro lens that has a longer focal length for more working distance. -
What is Macro Photography | What is a Macro Lens | Sony US
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so a 35mm macro has a shorter working distance than a 50mm macro which has a shorter working distance than a 100mm macro but all might be capable of 1:1 magnification
if you are photographing an object that doesn't move, that is one thing, one that moves and could be spooked by how close your are - well that is another