Photographers: Can you tell me what difference between a 50mm 1.8 and 50mm 2.5 lens for Canon?

The f1.8 lens (assuming this is a fixed aperture, and not adjustable to different f-stops) will be suitable for work in low-light conditions, since its opening to permit light is larger than an f-2.5 lens. However, it will also have a very shallow depth of field, meaning that anything that’s not directly focused on (at anything less than “normal portrait distance”) will be blurred.

So, for close up work, which you indicate you like to do, the higher f-stop lens will give you a deeper depth of field, if only slightly.

@CWOTUS Thanks, yeah I like the feel of the blurry backgrounds.

The 50mm f2.5 is a genuine macro lens. That version hits a 1:2 ratio and requires a dedicated converter to reach 1:1.

Macro lenses can be used as regular lenses. There is no compromise on sharpness, in fact most tests reveal macro lenses as actually a little sharper than standard prime lenses… especially that 50mm f1.8 primes (which is the low end model).

Standard prime lenses have what’s called field curvature… whereas the critical focus plane is shaped as an arc… it’s curved to varying degrees depending upon each lens. So if you photograph a brick wall 20’ away, and focus precisely in the center at 20’, then the sides of the wall will be slightly further away from the lens nodal point at say 22’. But the field curvature of the standard prime will still focus at 20’, which means critical focus will be lost the further from center they are.

Macro lenses are flat field… so when the center is focused at 20’, the far sides focus to 22’ (or so), and that will allow the brick wall to be crystal clear from edge to center to edge. This makes them very well suited for copying artwork or flat subjects like distant landscapes. And of course a macro lens will focus much much closer than a standard prime. They also have extremely good image quality (IQ) at close focus distances. The Standard primes are optimized for medium to long distance focusing, and their image quality suffers at close distance unless they have a floating element design… which this Canon f1.8 does not have.

Standard prime lenses get past the field curvature with depth of field at smaller apertures around f8 – f11. But in regular shooting, they are faster with brighter f/stops for low light shooting.

Standard primes have a smoother quality of bokeh (out of focus areas – oofa) and it is very pleasing to the eye making for a photograph with more depth and dimension.

Macros, with flat field capture tend to render an image more clinical and hard edged. They draw a photograph extremely sharp, but with less romance and artistic interpretation.

Standard primes render more like the human eye.