Semit-extreme macro: a birch catkin

[DanK]

There has been some discussion of extreme macro here the last few days. Got me thinking. When I was first learning macro, I tried to move continually closer as I learned more. However, over time, I simply lost track of that and simply chose a distance that gave me the image I wanted. The discussion here got me thinking about closer focusing.

And as chance would have it, I found a river birch catkin on my drive today while I was cleaning up. A catkin is a long, slim cluster of many typically small flowers. So, I took it in, put 76mm of extension tubes on a 100mm macro, moved fairly close to minimum working distance, and took this.

I don't think it's particularly attractive. It's also a fairly quick edit. However, I think it's interesting. The catkin is approximately 7mm wide, and this is cropped only on the long dimension, so that gives an idea of the magnification. I'm only guessing at the anatomy, but I think the flowers are the tiny green structures underneath the red-tinged scales.

This is 35 shots, stacked with Zerene PMax. DMap couldn't handle some of the distances well, and even with touching up, the PMax looked cleaner. Given the limited color, there wasn't any real advantage to the DMap composite anyway.

[billtils]

Dan

Your image made me pause and step back a bit, to explore what can be done with the tube set and my lenses. Here's the first data point: I've no idea what this is. It has sprouted in a pot left over from last year and I found it when tidying up in preparation for some lawn repair work. It is a single shot taken hand held with the 50mm prime with the 36mm extension tube attached.

The floral part is approx 0.8cm wide, the image here is approx 25% of the captured image, and the shooting distance was about 10cm.

[DanK]

Bill,

My understanding is that the standard formulas for magnification don't work at close to minimum focusing distance for macro lenses, and they certainly don't work for reversed lenses. In theory, a given length of extension should matter less, as effective focal length increases, but that hasn't been my experience.

The simplest way to get an estimate is to take a photo of a ruler, since you know the size of your sensor.

In this case, I measured on screen, and the catkin is very roughly 60-65% of the width of the frame, which is 24mm in a FF camera. So doing the arithmetic, it seems that 76 mm of extension on the 100mm lens got me just over 2:1 magnification. I should test this more carefully.

BTW, the way I got 76mm is that I started with a standard Kenko set, which has 36, 20, and 12 mm tubes that can be stacked. After years of use, the 36mm started to fail to make contact, so I bought another set. This gives me on 36 mm and 2 each of 20mm and 12mm.

Dan

[Chataignier]

Interesting - I too had read that extension tubes affect short focal lenses more than long focal lenses so I'd never bothered to buy extension tubes for my 100mm canon macro lens. I think I'll give them a try.
I use the canon lens on a Fuji X-T3 by the way, with a Viltrox adaptor that gives me auto-focus (that I never use) and stabilisation (that I do use).

[DanK]

I've seen several equations for estimating magnification with tubes, and I haven't dug into them to see which is right. However, it's definitely the case that a given length of tubes will provide more magnification with a shorter macro lens, given that most true macro lenses have the same magnification.

I've found that 36mm with the 100mm lens is a good amount of magnification for chasing bugs.