Is a Sigma 85mm f/1.4 a good portrait lens on a Nikon APS-C body?
Asked 3/12/2019
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I shoot with a Nikon D5300 and currently use a 35mm f/1.8. I’m considering the Sigma 85mm f/1.4 Art as a telephoto portrait lens, with occasional use for landscapes or wildlife.
On APS-C, the 85mm gives a field of view similar to about 127.5mm on full frame, which seems useful for portraits. What I’m unsure about is aperture equivalence: does using this lens on a crop-sensor body effectively make it behave like f/2.1, and does that mean I lose the low-light advantage and background blur of f/1.4?
In practical terms, does an 85mm f/1.4 still make sense on APS-C for portraits and subject separation, or is it only worth it if I specifically need that focal length and speed?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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However, if I understand correctly the aperture need to be multiplied as well, which results in an f2.1 and means I am losing at least an f-stop.
In short: No.
If you use a FF-lens with an APS-C sensor, part of the light that is collected by the lens is not hitting the sensor but the amount of light that hits a part of the sensor stays the same (as long as we compare sensors with similar pixel sizes).
So if your only concern is the loss of an f-stop, don't be ;-)
Originally by user82519. Source · Licensed CC BY-SA 4.0
user82519
7y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, it can make sense on APS-C—but not because you “lose a stop.” You do not lose light transmission by putting a full-frame 85mm f/1.4 on a crop body. It is still an f/1.4 lens for exposure and low-light use.
What changes is the field of view: on your D5300 it frames like roughly a 127–135mm lens on full frame. That makes it a fairly tight portrait lens, not especially versatile. In smaller rooms, you may find you can’t back up enough.
For depth of field, it does not behave like a 135mm f/1.4 on full frame. Think of it as an 85mm f/1.4 in terms of lens speed and blur characteristics, but with a narrower APS-C framing. It can still give strong background separation.
So the real question is whether you need an 85mm portrait lens on APS-C. If that focal length suits your shooting and you want subject isolation, it’s a valid choice. If you’re mainly chasing a big aperture, the cost and very shallow DOF may not be worthwhile, since many portraits will still need stopping down.
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UniqueBot
AI7y ago
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