can you please tell me which magification on lens is best for macro 0.2 or 0.24
Many times we wish to make close-up pictures of objects. Think about imaging coins or stamps or insects, or other objects that relate size-wise. You might find this task difficult unless your camera sanctions close focusing (many do not).
Macro lens to the rescue: A macro lens is optimized to make close-up pictures. Most will allow you to make a life-size image of objects. What do we mean by life-size? Say postage stamp measures ½ inch square (12mm by 12mm). If we were to image this stamp at life size, the stamp’s image, as projected on by the lens onto the surface of the imaging sensor (or film) would measure the same size as the object being photographed. In the jargon of photography, we say the image size equals “unity” or “actual size” or “life size” or “magnification 1”. Sometimes we write this fact as a ratio “1:1”, meaning the image of the object is reproduced the same size.
So what if we image a postage stamp with a lens set to deliver magnification 0.2, what does this mean? Say the stamp measures 12mm square. If we image at 0.2 magnifications the image of the stamp will measure 12 X 0.2 = 2.4mm height and 2.4mm length. If on the other hand we changed the lens setting to deliver 0.24 magnifications, then the image size that results will be a square 12mm X 0.24 = 2.88mm in size.
So what is the difference? 0.2 magnification images this stamp 2.4mm square. 0.24 magnification images this stamp 2.88mm square. The difference is an image size variance of under ½ mm. I think you will agree not much difference. Additionally, I will bet, no one can detect any significant quality difference between these two settings.
While it depends on what you're trying to fit into the frame, usually the bigger the maximimum available magnification the better - if you want less magnification, you can always take the picture from a longer distance.
Dedicated macro lenses (aka "Micro" lenses in Nikon terminology) usually allow you to go up to 1x, giving you a lifesize image on the sensor. I believe canon do a lens that can go up to 5x or so.
It sounds as though you're talking about normal lenses that have a good close focus ability - these are often marketed as "macro" models even though they don't allow a 1x magnification.
It all depends on what sort of things you want to photograph. If you want to take pictures of very small things, then you may want one of the dedicated macro lenses. If you want to take pictures of mid sized things like larger flowers and butterflies then your 0.2x or 0.24x lenses may do what you need (Though you might find you want more magnification).
One thing to bear in mind is the "working distance" - the distance from the front of the lens to the subject. Dedicated macro lenses are often available in around 50-60mm, 100mm, and 200mm focal length. At maximum magnication, a 50mm macro will be very close to the subject, a 100mm will be fairly close, and a 200mm will be further away. This doesn't matter too much for inanimate objects, but can be important if you're trying not to frighten an insect away. It may also cause shading problems if the camera blocks your lighting.
At lower magnifications, you can be further away. I've found my Nikon 80-400VR lens makes a fairly good butterfly lens - at 400mm, it allows you to shoot from a decent distance, though a bit more magnification would sometimes be useful. 500mm mirror lenses with a close focus also do well (the later Nikon 500f8 mirror lens, or the Tamron 500f8 adaptall mirror lens), though MF makes it somewhat more challenging.
If looking at a dedicated macro lens, I'd suggest going for 100mm or longer if your budget allows unless you're only shooting static subjects.