Macro lenses on DX bodies?
- Thread starter Elliot87
- Start date
Magnification is a result of focal length and focus distance.
The longer the focal length the greater the magnification.
The shorter the focus distance the greater the magnification.
A macro lens simply focuses closer than other lenses resulting in a greater magnification.
At 1:1, 1 millimeter of subject covers 1 millimeter of sensor, 10mm of subject covers 10mm of sensor, etc.
A shorter focal length macro will have a closer focus distance than a longer focal length macro if both are 1:1 lenses.
The longer the focal length the greater the magnification.
The shorter the focus distance the greater the magnification.
A macro lens simply focuses closer than other lenses resulting in a greater magnification.
At 1:1, 1 millimeter of subject covers 1 millimeter of sensor, 10mm of subject covers 10mm of sensor, etc.
A shorter focal length macro will have a closer focus distance than a longer focal length macro if both are 1:1 lenses.
BackdoorArts
Senior Member
You still get 1:1, but it will appear more magnified in the final image assuming both FX and DX cameras have the same number of pixels.
(and here we go again....)
(and here we go again....)
Not if printed at 1:1. The DX print will simply be smaller than the FX print regardless of pixels.
See, it's all relative. We can always add a twist, but the simple answer to the question is, yes, the 1:1 is maintained.
Just to confirm, the close focus distance of any lens stays the same regardless of whether it is on a FX or DX body?
Bear in mind this does not mean the shorter focal length lens magnifies greater. The magnification would be the same at 1:1.
Correct.
BackdoorArts
Senior Member
Like I said, here we go again...
Yes, because the DX is a smaller frame to fill.
If you used the same lens on a both and printed the images life size 1:1, then the DX print would be smaller and overlay perfectly on the FX print. The subject size would be the same.
Here is a diagram representing the same lens at the same focus distance producing a 1:1 image. The FX sees more and records more of the subject, but the magnification remains 1:1 (1mm of subject to 1mm of sensor image)
If you were taking a photo of a flat object like copying a page from a book, at 1:1 you could remove the sensor from the camera, lay it on the book page and it would cover the image you would have captured perfectly.
If you set the camera up at a 1:1 focus distance and then drew a rectangle around the view on the page with a pencil, the rectangle would be the same size as the camera's sensor. The FX rectangle would be larger than the DX, but the two would have the same center image.
If you set the camera up at a 1:1 focus distance and then drew a rectangle around the view on the page with a pencil, the rectangle would be the same size as the camera's sensor. The FX rectangle would be larger than the DX, but the two would have the same center image.
1:1 means that a 20mm object will be 20mm on the sensor. The DX sensor is 24mm wide while the FX sensor is 36mm wide. So a 36mm object will just fit the FX sensor, but overflow the DX sensor - 6mm on each side (if you centered it) will be cropped.
The same applies to all lenses. If the magnification of a telephoto is 1:0.01 (that 1/100), then a 1 meter object will be 1cm on the sensor, and 2.4m will be 2.4cm = 24mm : full DX width. If both DX and FX have same number of pixels - 24MP, then 24mm on DX will take up 6000 pixels while in FX it will take 4000 pixels, hence DX will appear to have magnified the image (assuming same number of pixels per print/display) by 1.5 times. This is where the confusion starts.
The same applies to all lenses. If the magnification of a telephoto is 1:0.01 (that 1/100), then a 1 meter object will be 1cm on the sensor, and 2.4m will be 2.4cm = 24mm : full DX width. If both DX and FX have same number of pixels - 24MP, then 24mm on DX will take up 6000 pixels while in FX it will take 4000 pixels, hence DX will appear to have magnified the image (assuming same number of pixels per print/display) by 1.5 times. This is where the confusion starts.
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Bob Blaylock
Senior Member
I would take a 1:1 ratio to mean that the lens is positioned so that the image formed on the film/sensor behind it is the same size as the subject in front of it. To look at it a bit differently, the area of the subject covered by the image would be the same size as the frame of the film or sensor.
An 8×10 view camera configured to take a 1:1 macro shot would cover an area eight inches by ten inches. A 35mm film camera configured for a 1:1 macro shot would cover an area 26 millimeters by 24 millimeters. My DX-format D3200 would cover an area 23.2 by 15.4 millimeters.
If you could get one lens, that would work with all three of these cameras, and was configured for a 1:1 macro shot, then it would truly be a 1:1 macro shot regardless of the size of the frame. The size of the frame has no bearing on this ratio. What the size of the frame does affect, given a particular ratio, is how much of the subject in front of the camera is covered in the picture. Again, with a 1:1 ratio, the area of subject covered in front of the camera would be the same size as the frame on which the image is focused.
But really, this ratio isn't nearly as meaningful as it seems. You're rarely going to print or display any picture at the size of the film frame or image sensor used to record it.
Yes, the working distance in front of the same 1:1 lens is the same on either body (it is the same lens), and the lens can still do 1:1 magnification on either sensor. The DX frame simply crops the overall frame view smaller than FX. But the object can be the same 1:1 size.
Ignoring the crop size in that 1:1 way is in contrast to the common knowledge that we have to stand back 1.5x farther with same lens on DX, or use a lens with focal length 1.5x longer on FX, to see the same view. But that specifically compares the cropped frame size view (seen in the smaller and larger frames), where 1:1 specifically describes the object size in either frame, regardless of how it might be cropped.
In film days, 1:1 means the image is the same size on the film as the object in real life. Take the film out, and a 1:1 photo of a US penny measured the same 3/4 inch diameter either way, on film or in real life. A penny at 1:1 will measure 3/4 inch on 35 mm film, and on 8x10 inch sheet film (that is the real life 1:1 size of a penny). At 1:1, you need an object 8x10 inches size to fill an 8x10 inch frame.
With digital, we cannot take the film out and look at it, but it still means the same thing.... if we photograph a ruler to see it, a 24x16mm DX frame will capture a 24x16mm area at 1:1... Or a 36x24mm FX frame will capture a 36x24 mm area at 1:1. And the object size in that (possibly cropped) frame will be 1:1 (real life size) either way.
If we enlarge and print both the DX and FX image, enlarged the same degree, the FX print will be 1.5x larger than the DX print... but the penny or ruler at 1:1 will be the same size in both prints (an enlarged size, but same size).
But if we enlarge the smaller DX image more, to print it same size as the FX print, then the DX print shows the object larger, which mimics a telephoto effect (cropped, then enlarged to same size). But it definitely is enlarged more then, which has adverse effect on image quality.
There are always some that imagine the sensor frame size does not matter, that it only matters how many megapixels we capture either way. They are of course hugely wrong.
Pixels do not create the image of course, the lens creates the image. The pixels simply attempt to sample the existing image sufficiently to reproduce it digitally (that image which has a size on the sensor), and it is that lens image in the sensor frame that is significant, which we try to reproduce with pixels.
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SkvLTD
Senior Member
TL;DR:
DX vs FX 1.5 crop factor has ONLY to do with the field of view you get out of a given lens. Using FX lens on DX sensor simply will not utilize its full possible field of view hence why a 50mm on DX is like a 35mm on DX. (so sideways/up-down what you can see through the lens)
Macro, as everyone said, has ONLY to do with the distance from sensor to subject that the lens can still focus on (forwards/backwards distance). At 1:1, the subject will be recorded at its actual size however well the sensor can fit it.
DX vs FX 1.5 crop factor has ONLY to do with the field of view you get out of a given lens. Using FX lens on DX sensor simply will not utilize its full possible field of view hence why a 50mm on DX is like a 35mm on DX. (so sideways/up-down what you can see through the lens)
Macro, as everyone said, has ONLY to do with the distance from sensor to subject that the lens can still focus on (forwards/backwards distance). At 1:1, the subject will be recorded at its actual size however well the sensor can fit it.