Image circle and sensor coverage chart. I am sure you have seen this before. But just a reminder that if you happen to own m43 camera, the vintage/cine lens image circle should do greater than 22mm diameter-wise for adequate coverage. So far for m43 cameras, there are only few lens that do cover the sensor that is less than 25mm focal length. As such, most len of those len will vignette on m43. A simple math can figure out adequate image circle for other sensors: bmpcc and pentax Q, assuming 25mm image circle is for m43. Bmpcc has about 2.9x crop factor and pentax Q has 5.6. As such, for bmpcc, 25/(2.9/2) = 17.2mm minimum image circle, and for pentax q = 25/ (5.6/2) = 8.9mm minimum image circle. One more thing: image circle is NOT focal length BUT you can use it as an estimate ballpark of which len will vignette. For example, since the minimum circle for pentax Q is around 8.9mm, generally you want to avoid prime/zoom len lower that has lower focal length than this number since they will vignette (e.g. generally you should avoid len lower than 9mm for pentax Q; exception can be made for modern len or LARGE/wide diameter front element or super 8 zoom lens, or rainbow 3.5mm len). For modern len, its easy to identify since you can just consult manufacturer lens specs of which sensor it is design for. (again, m43 should pick 1 sensor, pentax Q should go for 1/2 --although you can also do with 1/3 but it will vignette on wide end. )
Posted on: Thu, 21 Aug 2014 01:27:33 +0000
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