Ok, VUEmbers .... here is the thing. I am big advocate of doing
things with own hands and to verify stuff before I start believing on things
over the internet. I often heard and read from the internet that larger the sensor, shallower the depth of field. So i thoughts lets test this and see what exactly happening in the world of photography by having 3 different digital formats. Here is the breakdown with real-world examples of the
following 3 digital Format,
From
Left to Right,
Full
Frame:
Nikon D700 + 24mm f/1.4G
APS-C: Fujifilm X-T20 + 16mm f/1.4
Micro
4/3:
Panasonic GH5s + 12mm f/1.4
All these 3 digital formats cameras are covered by their respect
focal length lenses which covers the same angle of view (84 degrees) which are 24mm
(for full frame), 16mm (for APS-C) & 12mm (for Micro 4/3). All these 3
lenses are having a maximum aperture of f/1.4 in common, which means they pass
the same amount of light regardless of being the different focal lengths in
reality. Therefore, the exposure on all 3 formats is the same except that Nikon
highlights are little more than usual (my mistake). Settings on all 3 formats
cameras were as follows,
ISO:200
| f/1.4 | 1/100
Now this quick test I did is not for the quality of the Bokeh or
how lenses/sensors are rendering the image. It's more about why the depth of
field (Area in focus) is different in all 3 images regardless of being three
f/1.4 lenses in common.
Now some of you already know the answer in detail and most of
you will say well it's because of the bigger sensor size. Well in reality (and as the caption of this blog says) sensor size has nothing to do (directly) with the depth of field. As three
different formats capturing 3 different "area or angle of view" in
the real world, therefore, in order to obtain the "EQUAL" angle of
view we have to design the lenses with different focal length which ultimately
leads us to the famous term of "crop factor". Now let me clear at
this point right away that this crop factor has no connection what so ever with
the depth of field. It is just a reference to understand and bringing down
different digital formats at one level. It's just like if someone ask you how
many centimeters in 1 inch and you quickly say it's 2.54 centimeters or 25.4
millimeters and all will give you equal length in physical world.
1 inch = 2.54 centimeters = 25.4 millimeters
Same goes for the angle of view. All below 3 focal lengths will be giving me the same angle of view.
24mm (FF) = 16mm (APS-C) = 12mm (Micro 4/3)
Are you guys with me so far? I hope so. Now the big question is
why depth of field is changes by changing the format regardless of having f/1.4
lens. The answer is FOCAL LENGTH. As we
know that depth of field is changes by the following 3 parameters.
- Aperture (All were f/1.4 in this case)
- Distance of shooting (were the same in all 3 cases)
- Focal length (longer focal length produces
more shallower Depth of Field)
So, as you can see, when you change the format and try to
achieve the same angle of view by keeping aperture constant, the only parameter
which is makes the bigger impact practically speaking is the focal length. This
is why when you move to medium or large format cameras and try to achieve the
same angle of view with constant aperture, you will end up using longer focal
length lenses on the medium/large format cameras causing massive shallow depth
of field which make these format stands out. You can check sample image of the
medium format using this link where image was taken
by Fujifilm GFX 50R with 45mm f/28 lens (equivalent to 35mm f/2 for full
frame, or 23mm f/1.4 on APS-C).
Now let me share with you the 3 examples next which I took using
the same aperture, shutter speed and ISO value also from the same distance.
APS-C
Micro 4/3
I hope you will find information useful and it will help you in
making great images. If you still kind a confuse and not able to get what i explained, then i suggest to check out this video from fstopper.coom people who explained it well then me i guess. Please do visit our Facebook group VUE for more technical stuff related to
Photography.
Happy
Clicking Guys.
Babar Swaleheen
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