Macro photography

Started Apr 19, 2012 | Discussions thread
photonius
Veteran MemberPosts: 6,109
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Re: Wrong again....
In reply to filmluvr, Apr 24, 2012

filmluvr wrote:

photonius wrote:

The focal length of a lens does NOT make a difference, both 60mm and 100mm go to 1:1. So, yes, you are right, an object on the crop will cover more of the frame 1.6x than on the ff. That's why you get more apparent magnification with the 60mm on crop, the smaller sensor.

I understand the concept of apparent magnification, but when I first purchased the 60mm, I measured it with the 40D by shooting a machinest rule at minimum focus distance. I distinctly remember not seeing a 1.6 multiplier in the result, so I concluded that Canon's specification for magnification included an adjustment to produce the same image size as a percentage of the cropped frame. Unfortunately, I no longer have those images, nor the body or lens.

Well, I did measure a ruler once with the 60mm macro on a crop body, see
http://photonius.wikispaces.com/Close-up+%26+Macro
in particular:

The image I got was about 22mm in size horizontally. You can see the millimeter scale at the bottom on the left side (the right side is a 100% crop, not relevant here)

If I put a 100mm macro on this crop body, I would also get 22mm (both lenses go to 1:1). I do have an old FD 100mm macro from the film days that does this (with a glassless FD to EOS adapter).

If you put the 100mm macro on a FF body, the image you can capture horizontally is about 36mm (of the ruler) (just looking through the viewfinder of the film camera - I have no FF dSLR.

I'm not unwilling to admit mistakes though, and the answer to this is important for some of the work I do. So, as a result of your and brightcolours's last posts, I researched further online. Among other things, I found an image of a common item that had been shot with the 60mm at full magnification. I reviewed the same item on full frame at full magnification with my 100mm a few minutes ago, but even with a 25mm extension (should give me about x1.4), I can't quite equal the image size relative to the frame. So, with no other evidence at the moment to support my claim regarding frame size, I'll have to agree with you on these points: The X1 magnification quoted by Canon does indeed represent the object size VS size of the image projected onto the sensor, and it will be that size and ratio regardless of the format. Also, as you stated initially, this is the magnification of the lens proper, not the system as a whole. I'm kicking myself for not keeping the old test images, but that's life. Perhaps I did something wrong, perhaps not. I've been shooting quite a few years, and this wasn't the first time I've made measurements of this sort. Thanks for insisting you were right and for keeping it civil. Be warned though, if I find evidence to the contrary, I'll be back.

I don't know where your measurements did go wrong, but I'm sure you won't find evidence to the contrary

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