Olympus 75f1.8 is such a remarkable lens (except pricy) Lots of photos and image

Started Jul 28, 2012 | Discussions thread
tt321
Senior MemberPosts: 2,744Gear list
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Re: Say what?
In reply to Tim in upstate NY, Jul 28, 2012

Tim in upstate NY wrote:

tt321 wrote:

He's not a troll, and being stubborn is a good thing when he is right.

If light gathering ability per the entire sensor (rather than a unit area) is the metric, then 75/1.8 on M43 has roughly the same of this ability to a 150/3.5 on FF.

A unit area of the sensor is less meaningful than the entire sensor if both images are going to be enlarged to the same size print eventually.

On the other hand, if you use M43 to print to 8x10 and FF for 16x20, then 75/1.8 on M43 is the same as 150/1.8 on FF in light gathering ability.

. . . Light gathering ability is a meaningless term when used out of context and without adequate clarification. Exposure metering works the same with all sensor formats. f/1.8 is always f/1.8 when metering for the exposure setting. Your f/3.5 FF combo can't handle bad light as well as f/1.8 & m4/3 and yes it's that simple with no further clarification needed.

I was not bringing up "light gathering ability" but the one trying to qualify it. The qualification is "if you print to the same size". If the same size print is made from these two different systems, light gathering ability is measured in how many total photons contributed to each print eventually. In this regard, for the same scene exposed under the same light, the same number of photons will hit each sensor with 75/1.8 on the M43 and 150/3.5 on the FF.

You can expose the smaller system at ISO200 and the larger one at ISO800 for the same shutter speed. Then because of the smaller enlargement factor for the larger sensor, the prints should in principle look the same.

This assumes the larger sensor is four of the smaller sensors amalgamated into one. It's not without reason. Technically this discussion is about light gathering ability of lenses and format, and not sensor tech.

. . . DOF is always different when comparing different sensor and film format sizes - so what?

The first part is indeed a fact if you meant same FL and same F number. The "so what" bit I don't understand. The only possible answer seems to be to repeat the fact, i.e. "so the DoF is different"

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