????Macro Question????

[Mack1time]

I am slightly confused.

When a lens like the 100mm claims 1:1 Ratio
What does that actually mean?
Clearly when looking in the viewfinder your subject is magnified so how is this 1x?

Also on the mp-e-65mm macro lens that shoots 5x lifesize things look 200 times larger on my comp screen?

Please Explain?

[dpastern]

1:1 means life size on the negative (or digital frame). So, if your subject is 10mm long in real life, then it will appear as 10mm long on the negative/digital frame, i.e. exactly the same dimensions as the real subject. With the MPE-65, at 5:1 (i.e. 5x) a 10mm subject will appear as 50mm long on the negative/digital frame.

Dave

[macro junkie]

mpe-65 at 5:1 life size

http://farm3.static.flickr.com/2261/2403659595_ccfde8a76f.jpg



canon 60mm at 1:1

http://farm3.static.flickr.com/2153/2387616582_fcd78e643a.jpg

[20droger]

The ratio is a film thing. What a 1:1 ratio (1.0× magnification) means is that a 1 cm object will be 1 cm on the film (actual life size), not on a print made from the film.

The ratio kinda loses its meaning in the digital world. In the digital world, a 1:1 ratio means that a 1 cm object will be 1 cm on the sensor, the sensor having replaced the film. However, unless you print your images sensor-sized (22.5 × 15.0 mm for a 30D), the image on the print will invariably be larger than the image on the sensor.

For example, when using a 30D and a 1:1 macro lens, the image of a 1 cm object on a 225 × 150mm (8.86 × 5.91 in.) print will be 10 cm.

This "print magnification" effect does not take away from the absolute precision and beauty of an image taken with a good macro lens.

[dpastern]

1:1 has NOT changed when going from film negatives to digital sensors. film negatives were printed at a particular size, and of course, depending upon the enlargement, the subject size increased. The same goes with digital photography - the only difference is the RAW file (etc) has no physical tangible existence like a film negative etc.

Dave

[20droger]

I never said that a 1:1 ratio changed going trom film to digital. I said the ratio lost much of its meaning in the digital world. 1:1 on film or on sensor is still a 1:1 ratio.

What has changed is that in the film world it was very commonplace to produce contact prints, especially for purposes of mensuration. Virtually nobody makes a "contact print" of a digital image. Enlargements of images obviously are made in both the film and digital worlds.

Therefore, if you wish to make exact senor-sized "contact prints" of your digital image (for mensuration purposes, perhaps?), feel free to do so. Such images are, of course, still arbitrarily sized, and are not contact prints in the sense used with film.

If all you are doing is producing enlargements of macro images for esthetic, rather than mensurational, purposes, then the lens magnification is irrelevant to the image.

One interesting detail is that digital images can more easily be precisely enlarged. That is, it is a trivial task to produce an uncropped digital image that is exactly a given size, or a given multiple of a sensor's size. This has been a great boon to the scientific community vis-à-vis mensuration.

[dpastern]

Contact prints were common? Maybe amongst a very tiny minority, but the vast majority of people never did contact prints, and probably didn't know what they were. Contact prints are really irrelevant to the discussion anyways - the whole 1:1 etc boils down to the size of the subject on the film frame/sensor - @ 1:1 it *will* be exactly the same size as the actual subject/object that was photographed. What happens in terms of printing from the negative/sensor is another story.

Dave