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This may be as simple as it sounds, but I would appreciate your insight;
If we have a 100mm macro lens that gives us 1:1, lifesize, magnification at a minimum focusing distance of 12 inches, and put it on a digital slr with a sensor that gives an image that is 1.5X 35mm film, will we get an image that is 1.5X lifesize? The answer seems obvious, but these things are seldom what they seem. Now, if we put a 1.4X Teleconverter on between the lens and camera, will we get 2.1X lifesize? If my math is correct, it seems obvious, is it so, or is there some complicated formula to say I'm wrong? However, if I'm right, if we take the image at a distance of 2 feet, will we get lifesize, 0r 1.05X lifesize? What I'm getting at here, is can we use the crop factor of the sensor, and the magnification factor of the TC to increase the focusing distance at which we will get 1:1 magnification? It all looks so straightforward to me, it's scarey.
PS: I have read Pete's excellent article on macro photography in the tutorials a number of times, but I am still left with doubts regarding these questions. Your input is appreciated.
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I think I can answer the first part of your question: a 1:1 ratio means the image on the sensor is the same size as the original. Having a crop sensor just means you only capture a smaller part of the image than on a full-frame camera - it doesn't become 1.5 times larger.
Of course if you print both images at the same size, the cropped sensor one will look like it was magnified more.
If the object is 5mmx5mm then the 1:1 means it will be 5mmx5mm on the sensor. The lens can fit on APS-C or 35mm bodies but the size of the sensor will not change the fact that the projected image is 5mmx5mm.
If you take the camera images from APS-C and 35mm and view them uncropped at the same size (on screen or print), then the size of the object on the picture from the APS-C will be 1.5x bigger but only because the sensor is smaller and so the total APS-C image is being magnified more.
In fact, this applies to all images on APS-C vs 35mm. The APS-C does not give an inherently magnified image compared to 35mm.
If you take the picture from 2feet away then you will not get 1:1. But you can use a t/c to do so - If I remember my optics from a lo-o-ong time ago, in a simple lens magnification is inversely proportiinal to the object distance. Whether this works with complex camera lenses I don't know.
A 1.4x teleconverter magnifies the image by 1.4 so the image of he object in the above example will now be 1.4x bigger (7mmx7mm).
I have no idea if this helps but have a read and let me know.
May I suggest that you think about what the ambiguous term, which appears to be readily accepted but rarely examined, "Life Size", actually means?
Mount Everest is a one big piece of rock but it looks tiny from the space station cameras orbiting earth and, when mountaineers are really close up to it, they can't take it all in.
Whenever I use my macro lenses I realise that, sometimes, close focussing distance makes for more interesting macros than sensor size. For example, I often use two prime lenses (100mm and 180mm, sometimes with extension tubes) but these never get as close as my Panasonic LX3 compact camera which produces lovely macro images at 1 cm away from the subject. Obviously the sensor size is tiny compared to my 5D and 5D mkII but it produces great results.
Maybe I should have more simply said; "It's all relative" or "The photograph is the thing not the camera"?
Sabreur and Mikehit have summed up the effect of using a macro lens on crop sensor compared to fullframe rather well with regard to the overall magnification.
I should add that there are some other slight differences to using a macro lens on a fullframe (35mm) sensor/film as compared to a crop sensor (1.5 or 1.6).
1) Depth of field - because the circle of confusion changes between fullframe and crop sensor the depth of field changes as well. In practical terms at 1:1 you get around one stop (in aperture terms) more depth of field with the crop sensor over fullframe.
2) Diffraction - somewhat in counter to the above point diffraction softening of images takes place around one stop (again in aperture terms) earlier with crop sensor as compared to fullframe. So where as most find f13 around the limit for depth of field vs sharpness on crop sensor fullframe can push to around f18 (those are canon values, reduce by one to two stops for Nikon cameras*)
So in short the bonus of crop sensor is somewhat outdone by the bonus of fullframe. Note that diffraction limits are always slightly debatable depending on the camera body, lens and the users own standards as well as output medium and editing process. Some will favour smaller apertures whilst others favour wider ones.
Now as for boosting magnification values of lenses you can use a few options:
1) Teleconverters - as stated these increase the maximum magnification by the same value as they magnify - 1.4 or 2 times. However unlike many of the other methods for boosting magnification, extension tubes let you keep infinity focus and also keep the same working distance/min focusing distance. Myself I often use a 1.4TC on my macro lenses for a little boost to magnification, whilst not hampering the image quality nor making the process harder (magnified images at the min focusing distance makes handholding harder because your hand shake is also amplified).
2) Extension tubes - work just like normal, though add their magnification to the 1:1 already attained by the lens. So you can get to around 1.5:1 if you add 50mm of tubes to a 100mm lens. Note that is a rough value only because macro lenses will reduce their actual focal length as they focus down to 1:1 so the actual magnification will be slightly greater than stated here.
3) Close up lenses/diopters/attachments/filters - work just like extension tubes, but give more magnification on longer macro lenses as compared to shorter focal length lenses. 100mm is typically the rough diviving point between these and extension tubes (when magnification gain the main aim). Raynox series (eg DCR250) and the canon series (500D) are high quality options to consider in this area (raynox make a large range of lower and higher powered options).
I've personally used these in combination with the 1.4TC for boosting my magnification (I prefer them over tubes because they are faster to add/remove - esp the raynox with the clip adaptor)
4) Reversing lenses - yep nothing stops you reversing a good 50mm prime or a 28mm or anyother onto the front of a macro lens.
* In addition to the earlier stated focal length reduction, modern macro lenses also reduce their aperture as they near 1:1. So that by 1:1 most f2.8 macro lenses are closer to around f5.6 in their actual aperture. Nikon cameras report this change to the user, whilst Canon ones don't. This means that at 1:1 there is always the 2 stop difference in aperture between the readouts of the two camera brands - with possibly the only true f2.8 macro lens on the current market being the MPE 65mm from canon.
very useful info above.
If anyone's interested: When taking photos of a ruler or tape measure (!):
if I put my 105mm Vr + 67mm extension tubes on a Cropped camera (D200) the most magnification I can achieve is about a 10mm wide image.
If I put the same combination on a full frame camera (D700) the most magnification I can achieve is about a 15mm wide image.
Exactly as stated above.
Forget the teleconverter. Use an extension tube if you have to.
Quote: Forget the teleconverter. Use an extension tube if you have to.
what about the reduced minimum focusing distance and the loss of infinity focus that the extension tube will bring with it?
Well, that answers some of my queries, but what I'm looking for is whether the math is as simple as it looks, eg., If you have a 100mm lens, and the focal length ends up doubled with the crop factor, and accessories, will I still get 1:1 at double the distance, eg., 2 feet from the subject? A TC should still allow infinity focus, should it not?
The magnification won't change because of the crop factor of the lens - remember magnification is a ratio of real life size against the size of the image that the lens creates. This is fixed a 1:1 lens on a crop sensor body is still 1:1 on fullframe or any other sensor size you'd care to try.
However this is only true in so far as the capture - when it comes to printing the results if you print a fullframe photo and a crop sensor photo (both taken at the same magnification) to the same physical size the crop sensor will "appear" to be at a greater magnification (this is similar to how wildlifers get "more focal length" with crop sensor over fullframe).
To get true 2:1 from a teleconverter you will need a 2*teleconverter - which will indeed mean that you get around 1:1 much further away than normal *you'll also get a really nice increase in background blurring).
Now if you want to get complex and compare prints and the apparent magnifications from fullframe to crop sensor that gets more confusing and I'm not sure what the results will show - though I suspect the simple math approach of simply getting 1.6 times the magnification will be about right.
My God Denny, this is all much too complicated! Just stick the bugger on, bang away & see what happens.
Quote: My God Denny, this is all much too complicated! Just stick the bugger on, bang away & see what happens.
Precisely my technique
totally agree, my head is starting to hurt!!
Lol; you guys are getting lazy.
Nope - I prefer to just go by experience and sod the technicalities
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