horsin visited me on site so i'll do the chanting again.....
ish a bored n tired thu afternoon
i'm a big fan of musselman
Last edited by juste_millieu; 18th March 2010 at 02:19 PM.
1. Circle of Confusion - As larger format tends to have a higher COC tolerant, this gives a position where optical energy are better maximised comparatively, (optimizing this position will then have to depend on the quality of the sensor). In reverse, this high tolerant also maintains resolution in the blurr out region resulting in a smoother fading effect giving rise to what is called creamier bokeh. Hence your first opinion that FF sensor is able to render better bokeh is correct.
2. Aperture - this is often overlook but the shape of the aperture does play a part in the presentation of bokeh. Generally, the rounder the better however it's a matter of preference e.g. the 50mm f/1.8 gives an interestin pentagon effect in the bokeh. Minolta adds a 2nd aperture in one of their bespoke lens, the legendary STF (which now Sony also produce) to vary the presentation of the bokeh. So it is said that if you can soften the edge of the aperture, the creamier effect can be achieve.
3. Distances - these are less direct technical consideration but more to attaining the impact of the technical specification. e.g. subject to sensor pane distant., background to subject distant., and the ratio of the mentioned example.
With lens, focal length, distants of subject/background ratio and aperture being constant, the larger format will still have a marginal advantage with regards to creamier bokeh quality based on their higher CoC tolerance.
In real life comparison, the photographers shooting the same frame with the same lens and apperture i.e. both shooting head and shoulder shots for example, will create a more distinct difference as the distances now comes into play. This same lens focusing at different distance will have different DOF resultant values as each altered their focal point position against their Hyperfocal point.
Below is the calculated DOF of a typical 50mm at f/2.8 on the selected format (sensor pane to subject distant 2m)
D300 (1.92m - 2.09m) total 17cm
D700 (1.9m - 2.12m) total 22cm
I did not have my own calculator in this office comp, but found an online calculator for the above results. As you can see, the larger format provides a better DOF, but the difference in the CoC results in the creamier bokeh.
Online DOF Calculator
Last edited by jawzsg; 18th March 2010 at 02:39 PM.
P.S. for M/format calculation, a sensor such as the Mamiya 645 should have a CoC of 0.039 while larger pentacon would be in the region of 0.045
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I don't have a M/format cameller...but what the FX lens does on a DX cameller, the M/format lens does it better on the FX cameller... moi ish hwill lub chiu renz dipz dipz.....
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