Day: January 6, 2013

35mm lens on a cropped frame

When I bought my first APS-C sensor DSLR I wanted to buy my first prime lens.

I was told 35mm lens is equivalent to standard normal view 50mm on a 35mm sensor .. and the 50mm will be the equivalent of 75mm ..

I therefore bought the 35mm just to get the surprise of my life .. the 35mm lens did not behave like a 50mm when it came to perspective and distortion .. it kept its usual wider angle perspective .. just being cropped meant the image appeared as if it was more zoomed in due to the cropping ..

I returned the 35mm lens straight away and replaced it with a 50mm that behaved as expected exactly like a 50mm lens and not a 75mm when it came to perspective and DOF .. only the DOF was more deeper compared to the same lens and aperture on a full frame as it took the same shot from further away !!

Full-Frame or not

The ultimate in photography is not full frame sensor cameras of course .. they are the medium format or large format cameras .. However, for all practical purposes and as the 35mm full frame sensor cameras are the mainstream format and are still affordable albeit expensive .. our discussion will be between 35mm full frame sensors and smaller sensors in DSLR’s and other smaller interchangeable lens cameras.

Full frame has many advantages .. cleaner pictures especially in low light due to lower noise ratio .. higher image quality .. usually higher megapixel count all compared to similar cropped sensors .. and the ultimate is a more blurred out-of-focus background (Bokeh) compared to smaller sensors using the same focal length and aperture which in some cases can not be matched by same lens/focal length/aperture .. They also allows using smaller apertures (larger f number) before diffraction sets in and softens the image, although on cropped sensors you don’t need to go really small to get the same DOF  .. and less wide lenses for the same angle of view (a 10mm lens would be equivalent to 15mm on a cropped sensor) ..

Advantages of smaller (cropped sensors APS-C, 4/3 etc) .. less expensive  .. longer focal reach for same focal length (smaller sensors have a crop factor x1.5, x1.6, x2 etc) more useful in wild life and nature shots .. deeper Depth of Field (DOF) more useful for cityscapes and landscapes .. smaller bodies and more importantly less glass .. so smaller, lighter and less expensive lenses .. also using full-frame lenses on a cropped sensor means you get the sweat central spot of the lens in action and discard the soft periphery ..

So what do you go for .. I would say if you have the money you need both .. two bodies, one each .. if you are on a budget then a cropped sensor body .. and add the full frame in the future .. simply because the full frame gives you higher IQ, better low light performance and shallower DOF