What focal length macro lens?

Question

I'd like to try some macro photography with a DSLR that has an APS-C size sensor (such as a Pentax K100D). If I were to buy a prime macro lens, how do I decide between a 50mm and a 100mm macro? Or maybe a 70mm macro? I understand the basics of focal lengths, but how does the focal length affect macro photography? The lenses all seem to do 1:1 magnification, and the minimum focus distances are not too different.

Answer 1

You're right. The lenses will all do the job for macro photography. The first consideration is that the longer lens will require or allow - depending on your priorities - a greater working distance. If you are going to be shooting bugs or other living things like that, more working distance will allow you to be less intrusive. You won't scare the bugs or critters away. If you are shooting people parts, like eyes or teeth, some people might prefer to have you a bit farther away, so 100 mm helps. If you are outdoors, your own shadow will be less of a problem with the longer lens. You will have a shorter range of focus with the longer lens. This can be an asset or a problem, depending on what you are shooting.

One advantage to the shorter lens is that it costs less money. In the case of Pentax, I see it makes about $100 difference in the price from the 50 mm to the 100 mm. I also see a Sigma 70 mm that falls right in between the two Pentax lenses in price, but I don't see that it offers any advantage, especially considering that the minimum aperture on the Sigma is f/22 and both Pentaxes go to f/32. When you get down to 1:1 reproduction, you might just want that f/32 capability for increased depth of field.

Personally, I bought a Nikon 60 mm f/2.8 lens and I admit that it was partly because of the 60 mm cost $400 and the 105 mm cost about $600. Also, the 60 mm lens translates to an effective 90 mm focal length and this is "classic" for portraiture. I don't find the non-VR 105 lens, but I see the 105 mm VR macro lens costs $800. Man, I think I would have been tempted by that VR, but I doubt it. See, you're lucky. You have "shake reduction" built into your camera and us Nikon guys have to buy it in the lens...

Anyhow, you asked which lens to buy. I'd skip the 70 mm because it offers no price advantage and does not stop down as much as the Pentax lenses. After that, I'd say it is easier to hold the 60 mm still if you are not using a tripod, but your experience with shake reduction might tell you to go ahead and buy the 100 mm anyway.

Don't forget that you can use either lens for normal photography also, so decide if you'd rather have a 60 mm (equiv to 90 mm) or 100 mm (equiv to 150 mm) prime lens and buy that lens. 90 mm is in the "classic" portrait range for its working distance and perspective if that matters to you.

I see there is a manufacturer's rebate that runs until March 27. You get back a dollar per millimeter - $50 on the 50 mm lens and $100 on the 100 mm lens. Be sure your retailer offers this rebate.

Answer 2

I'm always impressed by Alan M's answers and he covers everything regarding focal length quite well.

I can only add that I have the Pentax 100mm Macro on and *ist DS (the predecessor to the 100D) and can't tell you how impressed I am with the build quality and the crispness of this lens.

I enjoy the 100mm focal length precisely because it allows me some distance between subjects, and again Alan makes a great point in shadow reduction (which I never thought of when I bought it but now that I use it makes perfect sense) since you're not standing on top of the subject.

The Pentax lenses perform flawlessly and the only downside is the weight/heft of the 100mm vs. the 50. This is a minor quibble really and I think you'd be happy with either.

Watch for rebates from Pentax as they generally will net you between $75-150 depending on the lens.

I've never used the Sigma 70mm first hand, but have had a couple of their lenses and used them with mixed success. I hate to "paint in broad strokes" in trying to compare disimilar lenses from the same manufacturer but I will say that the overall build quality, focusing and aperture movement of the Pentax lenses were better in my opinion.

If you were to allow me to spend your money I would buy the 100MM first, 50MM second, and the Sigma third.

Good luck!

Answer 3

The 50 mm will probably have more light, but it may have more perspective (making the front larger and back smaller) distorition. Probably the 70mm is a happy medium. IT' has a very flat field and a big aperature.

Answer 4

go to adorama.com
they have many choices in lenses
they will explain what each will do