I would like to know, using both setups to photograph the same object from the same distance, which 100% crop from the following two camera setups is physically larger (ie. looks larger or more magnified):
1) OM System OM-1 + Oly 100-400mm
2) Fujifilm X-T5 + Fuji 100-400mm
My reasoning only goes as far as the following:
A) the images are projected onto all the available pixels of the camera sensor
-- OM-1 is about 20MP, max. resolution 5184 x 3888 pixels (4:3 aspect)
-- X-T5 is about 40MP, max. resolution 7728 x 5152 pixels (3:2 aspect)
B) standardizing "focal lengths" of the lens in both systems:
-- M43 crop factor = 2X - 400mm on the lens = 800mm FF equivalent
-- Fuji APS-C crop factor = 1.5X - 400mm on the lens = 600mm FF equivalent
Now I am stuck ....
Obviously the image produced by the M43 system is larger (more magnified) than APS-C ("longer" standardized FL), but the smaller image of the APS-C is casted onto a much larger number of pixels (40 vs 20 MP, or about 2X more).
What I want to derive is: if you do a 100% crop OF THE SAME RESOLUTION (eg. 600 X 400 pixels), which cropped image appears larger? I wonder if this can be determined from calculation because I don't want to buy the cameras & lenses to find out.
From my calculations it turns out that using the OM System OM-1, you will get an image content with a slightly larger FoV (~1.09x) horizontally, compared to the Fujifilm X-T5. Larger FoV means lower magnification for the area of interest.
I hope I didn't miscalculate! 😎
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I made a simulation: X-T5/left - OM-1/right
So you are saying the absolute size of the image crops from the OM-1 combo is SMALLER than the Fuji combo? Is it possible to derive the percentage difference (eg. in terms of area or linear dimension) from FoV difference?
Can you explain the math behind your deduction (though I am no mathematician)? I cannot get around determining the mathematical relationship between sensor resolution (pixels) and focal lengths of the lenses (which I guess is associated with field of view (FoV)??)
Thanks.
P.S. I think I understand - the area difference is directly proportional to DISTANCE from the source, for a specific FoV. Therefore there is no absolute value, only a relative percentage difference.
Very simple speaking, if you crop the XT5 by 33% from 7728 to 5184, you could possible get the same AoV, i.e. similar size of an object.
In terms of magnification, M43 is larger because at 1:1 view, you should see an image taken at 800mm (equivalent focal length to FF) but it is only 600mm on APSC.
In terms of detail of hard copy print out the XT5 should have higher resolution than OM1, e.g. a 1" x 1" hard copy.
If you watch them on the same monitor, at 1:1, as long as the resolution of your monitor is smaller than 20Mp, you would see the same resolution of both output.
So, we have two cameras with sensors of different sizes and we photograph a subject at the same distance with the same lens, so with the same focal length.
The camera with a smaller sensor offers less content in the image compared to the camera with a larger sensor, depending on the size ratio between the sensors (calculated by width).
Between the APS-C sensor in the Fuji camera and the one in the OM-1 camera, we have a ratio of 1.364. So the OM-1 has a crop factor of 1.364 vs that of the XT-5 (17.3mm x 1.364 = ~23.6mm)
Making a crop of 1.364 relative to the number of horizontal pixels from what the XT-4 offers, results an image with a resolution of ~5666 pixels, horizontally.
The sensor in the OM-1 offers 5184 pixels horizontally. From this it follows that the XT-5 describes the same content in the image using more pixels.
If you crop to get content with the same number of pixels horizontally (the subject of the problem, e.g. 1200 pixels x 800 pixels), the image taken with the Fuji offers a slightly smaller FoV = a slightly higher magnification of the subject, if that interests you.
Thanks for the explanation, I think I am following you.
You are using the physical dimensions of the sensor rather than "pixels" and "crop factors (of the camera system)". This is probably most representative. And I also understand that when you use the term "crop factor" in your interpretation, you mean "crop factor" of the physical dimension between the 2 sensors.
Question:
I know both lenses have the same focal length, but why is it not necessary to bring "crop factor" of the two camera systems into consideration when you do your calculation? Surely the image obtained by the M43 lens is "larger" (at equivalent focal length on the lens) because of higher crop factor of the M43 system. This was one of the most puzzling thing I could not get around when I thought about the problem in the first place.
I did a rough measurement and find the linear (horizontal) dimension of the 100% crop from the X-T5 is about 1.09X that from the OM-1. This matches perfectly with the figure 3DGunner quoted in his original reply. Excellent, Mr 3DGunner sir!!
This means that the X-T5 +100-400 + full size crop images are equivalent (just slightly larger, but definitely not smaller) to the OM-1 + 100-400, despite a (APS-C system) crop factor disadvantage. I guess this is exactly the same principle behind "crop modes" of FF cameras and "smart zoom" of some other digital cameras.
P.S. Mr finnan's interpretation using pixel pitch is also correct, thank you!
Again, makes me wonder why none of these two interpretations involve "crop factor" difference between APS-C and M43 systems?
"Crop factor" differences between camera systems is irrelevant in the arguement because the physical properties of the two lenses (100-400mm) are the same, therefore the absolute FoV of both lenses are the same. This assumes both lenses cast an image of identical "size" (FoV) onto the sensors.
The M43 system has a shorter distance between the image focal point and the sensor, therefore the image casted onto the sensor is "less wide" and "appears" to be more magnified (when viewed in a picture utilizing the full sensor resolution) compared to the APS-C system.
This is the same arguement that the "absolute F number" (or light transmitting ability) of the lenses doesn't change with the camera systems (but the depth of field does, for the same F number in different camera systems, because this is the parameter affected by the distance between the focal point and the sensor).
Might be not related to the fringe focal distance.
M43 has a shorter fringe distance of 19.25mm vs most usual DSLR (due to no more mirror box). If your thinking is correct, how about an APSC mirrorless? Says, Fujifilm is only 17.7mm, or both of Canon EFM and Sony E mount are 18mm. But they have the same 1.5x crop factor (1.6x for Canon) whereas the longer fringe focal distance of M43 is 2.0x...
It is actually related to the size of the sensor and the crop factor, relative to FF system, is the ratio of their diagonal diamension. Detail please see : en.m.wikipedia.org/wiki/Flange_focal_distance
Although the fringe distances are varied among various lens mount, the design has compensated for the differences under the balances of size and length of the lenses in order to allow the image circle projected by the lens can fully cover the entire sensor surfaces. This is also why a smaller sensor size system can has smaller size lens.
Since focal length of a lens is the physical propert of every lens, equivalent AoV is determined by the crop factor. A good example is while a 50mm film MF lens been adapted on a FF digital camera, it has an AoV of 50mm. When it is adapted on a M43 camera, the AoV would become 100mm since only the center portion of the original image circle projected by the 50mm FF lens would be recorded by the smaller M43 sensor.
DoF is (partially) determined by the focal length of the lens. Take the example of the 50mm FF AoV, says if at X distance and DoF is (partially) determined by the focal length of the lens. Take the example of the 50mm FF AoV, says if at X distance and @f/N is AAm, since a 25mm lens will give equivalent AoV of 50mm on M43, the DoF of course will become 2x AAm because it is a 25mm physical focal length lens.
In terms of equivalent aperture, it is also very simple. Aperture size is determined by 1/physical focal length. A 50mm FF lens In terms of equivalent aperture, it is also very simple. Aperture size is determined by 1/physical focal length. A 50mm FF lens @f/2 has a diameter of 25mm. For an Eq AoV 50mm M43 lens, it is actually 25mm. To have an Aperture size of 25mm, the 25mm M43 lens has to be f/1.0. Alternatively speaking, a 25mm f/2 M43 lens has an eq aperture of f/4 of FF.
So it is all down to the crop factor, which is the size of sensor.
I think Bobn2 could give a very detail explanation on this.
Thanks for appreciation!
In the case of the problem presented by you, two elements are taken into consideration:
1. - the dimensions of the sensors
2. - the pixel density (per surface unit)
Crop factor and total pixel count have nothing to do with your question. Focal length and pixel spacing are all that matter. How could knowledge of where the edges of the frame are affect the pixels within it, or the size of an object on the sensor?
You might be making this more complicated than it needs to be. This is completely down to focal length and pixel spacing. Nothing to do with camera chamber depths, crop factors, or anything else. Hold a lens in your hand, in a dark room, and point it out the window at a tree. Take two sheets of quadrille paper, with different grid sizes, and project the tree on each of them, and keep cutting the sheets so they each get smaller. Through it all, the tree is the same physical size on both sheets, always focuses at the same distance from the paper, and only differs in the number of quadrille squares (and only because they are different sizes).
With the sensors that you mentioned, the "quadrille square size" is almost the same, with the Fuji being just several percent smaller in width and height.
I don't know how the idea that there is some optical magnification effect with crop factors came into existence, but it does not exist in reality.
