06-02-10 – Macro Bugs

I have a really cheap macro for my Olympus Four Thirds. It can do 1:1, but you have to get really close to do this. However, because of the size of the sensor, 1:1 actually becomes 1:2 (so I read). Does this mean that I cannot take “true macros”, only “half-sized”?

No, whatever you read was wrong.

Magnification, in photographic terms, is purely an artifact of the lens, not the camera body. At 1:1 magnification, the image projected at the focal planes on each side of the lens is the same size.

So on a full frame camera at 1:1 you can capture 36x24mm, and for 4/3 its 17x13mm, but the magnification in both cases is the same.

I see. So my macro, at full 1:1 extension, is a proper macro? That’s actually very nice to know.
If I stick an extension tube on, I get even more macro power?
Hmmm, maybe it’s time for a new toy.

I’m going to be sleeping with a can of Raid for weeks now.

Oh is that what that was?

No I think he was just happy to see you.

People confuse those two all the time. Or similar-sized cans like pringles or krylon.

There is a gold paint huffer joke in there somewhere.

Just call me Tribett….

this set shows my bellows and focusing rail in action on my Minolta XD-11. the bellows won’t fit my knoica/minolta maxxum 7D and i haven’t tried the focusing rail. the problem with using the focusing rail at mid travel on the bellows is that the rail itself will sometimes hit the subject. this may also occur with the smaller extension tubes. we shall see later today.

If I could just make one sleepy comment.

It is rarely appropriate to use auto-focus in macro photography. It is slow, uses up battery, and worst of all, as has already been mentioned, tends to focus on something other than what you wanted it to. I pretty much only use it if my subject fills up my frame fairly completely and isn’t moving. 😉 Other than that, it’s manual focus all the way. Tremendously less frustrating. I’ve found the easiest way to shoot moving targets or targets at the closest range the equipment is built for is to focus it as close as possible and then move me. I’ve found this this technique is great for plants moving in the breeze (although in that case I wait for the breeze to blow the plant into focus rather than moving myself) and that sort of thing.

Really, autofocus+macro=years off your life. 😉

If I could just make one sleepy comment.

It is rarely appropriate to use auto-focus in macro photography. (snip)

Really, autofocus+macro=years off your life. 😉

I have no choice. I dropped my macro lens and now the switch for auto/manual focus is broken. Woe is me.

I tried using the ‘macro’ lens that came with my camera taped up to a reversed ‘telescope’ lens of the same; I got much closer (up to 6 inched from 16″ with just the ‘macro’), but could not focus on my subjects easily; got focused around them, but in 80 or so pictures, never on them.

This is the kind of case where a “macro rail,” or “focus rack,” like this one comes in very handy.

I don’t have one. I’m planning on getting one.

Holy crap, batman!! If I had that to spend, I’d have a decent macro lens!! In truth, I’m more interested in fine-focusing afar than up close. But good to know they make such a product.

Well hm..on further reading of that lens review, it mentions the effective apperture is quite a bit smaller than stated aperture. I’m not sure how that works, or how that works without introducing a boatload of diffraction softening by f/5.6 or f/8. Damn all this math…

Yeah, the thing is that people talk about changes to “effective aperture” when talking about macro lenses, but that can actually be quite misleading. When you focus closer by moving the lens further away from the camera, you lose light due to extension (the lens is projecting a bigger image circle, so there’s more light getting lost inside the lens, and less light falling on the sensor/film). People tend to call this a change in the aperture because they’re used to dealing with exposure in terms of three variables and it clearly doesn’t fit into shutter speed or ISO, but it’s not actually affecting your DOF or diffraction the way an actual change of aperture would, it’s really just light loss due to extension (it’s called “bellows factor” in large format shooting: www-unix.oit.umass.edu/~rbhome/bellows15.pdf).

This doesn’t necessarily apply to internal focusing lenses though. They’re focusing by changing the optical formula of the lens which can alter the effective aperture (as well as shortening the effective focal length in many cases).