The best camera for macro?

Started Dec 27, 2012 | Discussions thread
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dsjtecserv Veteran Member • Posts: 3,063
Re: APS-C has an advantage

brightcolours wrote:

Here's something to read up on magnification:

"We've seen in the examples above that sensor size can be used to calculate magnification, but the degree of magnification itself depends on focal length and subject distance exclusively (assuming that the lens is not used with any extenders or magnifying filters). Sensor size does not alter magnification. With a fixed focal length and subject distance, an APS-C sensor, for example would just crop the frame compared to a full-frame sensor, not enlarge it. Magnification is a property of the projection, regardless of the size of sensor (or film format) you are using. With a full frame sensor you'd just make calculations using 35mm as the sensor width instead of 22mm, but the subject would then be proportionally larger, cancelling out the sensor size difference." [emphasis added]

You keep thinking the magnification of the lens is the only thing the thing magnification applies to. This is incorrect.

"Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one it refers to a reduction in size, sometimes called "minification" or "de-magnification".

Typically magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image."

Indeed, the smaller sensor does provide 1.6x more magnification of the object for the captured image. Whoever wrote that blurb on dpreview is not correct.

The smaller sensor does EXACTLY the same as an 1.6x TC will do. There is no difference. Yet, one thing you do consider "magnification" (the lens + TC), the other you do not consider magnification (lens with smaller sensor). The images will be exactly the same.

It is incorrect, to state that what I wrote is wrong. Magnification is just about how big a subject appears. The subject does not change itself.

Really, did anybody suggest that pointing a cropped camera at a bug made the bug bigger? Of course we are talking about the image of the bug, as projected on the sensor. And it is simply incorrect to suggest that the image of the bug gets bigger (as you did) when it is projected onto a crop sensor.

By shooting with a smaller sensor, and keeping the print size the same, you do magnify more. Same as with "zooming in" on an image on a computer screen... You do magnify more.

You enlarge more.

I did not write that the magnification OF THE LENS would increase by using APS-C, I merely was talking about total magnification as seen on the image captured/printed.

The image captured will be the image projected by the lens, and its magnification will not be affected in any way whatsoever by they size of the sensor. When you subsequently enlarge or and/or crop it further you will obviously be affecting the physical size of the printed image, which will have its own ratio to the original size of the object. But that is a matter entirely separate from capturing an image a 1:1 (or whatever), which is what magnification is concerned with.

The dpreview "blurb" is not incorrect; it reflects the established understanding of the use of magnification; and can be found in numerous other references. For instance (which also has a short discussion on how sensor size fits in to the subject). Magnification is, indeed, a function of the lens alone (specifically, its focal length and shooting distance). That doesn't exclude ​additional​ consideration of ​other​ things that affect the final image, but they have to be understood separately from magnification itself.

What you are referring to is sometimes generously referred to as "apparent magnification", which is how big something "looks" when all image making steps, including cropping and enlarging are completed. I think that this is, indeed, a legitimate consideration when viewing the entire photographic process. But the term "magnification" (also known as "reproduction ratio") is reserved for the ratio of the image of an object as captured on the recording medium, because it provides valuable information about the degree of detail potentially recorded, which could not be discerned one the image has been through additional steps of cropping an enlargement.

The problem with trying to apply "magnification" to the size of an image of an object relative to the frame, rather than relative the original size of the object is that cropping is not equivalent to projecting a larger image, any more than using a 50 mm lens on a crop camera turns in into a 80 mm lens. Knowing the actual magnification relative only to the object tells us much about the quality and degree of detail that we have recorded, which a ratio relative only to the frame cannot. That's why photography has traditionally (and continues to) look at magnification on the recording medium independent of subsequent factors such as cropping (whether by sensor or scissors) and enlarging. Making a complete macro photograph doesn't exclude those factors, but magnification does.


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