The truth about fast glass on m4/3

Started May 21, 2012 | Discussions thread
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Re: Who cares about the total light flux
In reply to headofdestiny, May 21, 2012

headofdestiny wrote:

Lights wrote:

headofdestiny wrote:

Lights wrote:
rr_hhh said:

You are just messing things up. Who cares about the total light gathered ( but perhaps the pixel peepers shooting at high ISO) ?

For all practical purposes, what is important is that the light intensity is the same : F2.8 on mft will require the same shutter speed as F2.8 on a FF or an APSC sensor.
DOF however will be multiplied by 2.

That is correct. A Fstop is an Fstop. The crew of the Starship Enterprise might indeed care about total light flux, since it might interfere with their neutrino beam communications network. The DOF changes, the light is the same for the given area.

The difference is that the 35mm will be (approximately) two stops cleaner when using the same ISO as m4/3. That's what many are failing to understand.

Again, using a 25/2.8 lens on m4/3 at ISO 100 will be equivalent to using a 50/5.6 lens at ISO 400 on a 35mm sensor in terms of both depth of field, framing, and shot noise.
Canon 1ds series 50mm lens (actual) focused at 10' at F2
DOF (acceptably in focus area) near: 9.33 ft Far: 10.9 ft Total: 1.45 ft.

Olympus EP series (applies for all 4/3) 50mm lens (actual) focused at 10' at F2
DOF (acceptably in focus area) near: 9.65ft Far 10.4ft Total .72 ft.

if you are using the same lens. If you are not using the same lens such as you are not, since a 25mm and a 50mm are not the same. Of course the focal lengths will come out differently with the same lens. The amount of light gathered is the same. F2 is F2. The amount of light however, falling on any given part of either sensor, is the same. The total area IS different, however I would think that read noise, shot noise or whatever else is much more dependent on the technology involved, since while it is correct that a larger sensor needs more "Total" light (it's bigger) the amount of light on a particular place is the same. Does the new Nikon with it's huge amount of Mp's suffer a great deal from smaller crammed pixels? I think not.

I also think it's time that this equivalency "c-r-a-p" is put to rest. Since people are shooting in the format they are shooting in...whether you or I or anyone. Also believing that if I were to shoot in large format, I would not attempt to compare it, it is a different format, with it's own problems and strengths (I have used it a long, long time ago, and not much) While comparing FF is relative to a degree to those who shot 35mm, just to get a 'feel' for what can or can't be done...we here in the M43 forum are shooting M43 cameras in M43 format. They have their own strengths and weakness. One of the strengths I like, is the "extended" DOF at a 35mm "equivalent" focal length at a wider aperture..while still maintaining the ability with a fast lens at an EFL to limit DOF. A balance. That is what many of us here, and on APS-C like.

Why would you put a 50mm lens on both a m4/3 camera and a 35mm camera and then stand in the same place to test?

The point is that, in terms of both depth of field and noise, this new zoom is just like buying an f5.6 zoom for 35mm, which would be small and very cheap...and certainly not $1400.

This isn't simply comparing formats. It has to do with dof and noise calculation. I use several formats, and knowing that m4/3 f2.8 approximately equals aps-c f3.8 approximately equals 35mm f5.6 approximately equals 6x6 f10 allows one to easily go back and forth between them.

Ok I agree, that for people who use multiple formats this all makes sense (and I do use a camera with a 2/3 sensor (and in good light at low ISO as good as many DSLR's or M43) and an APS-C). But the only difference, with equal sensor in DOF at a given EFL and aperture. To some people extended DOF at a given aperture is important (street shooters using zone focus-landscapers in dim light). To some people limiting the DOF is important (portraiture).

I think sensor technology, and processor tech, is way more important than how much total light hits the sensor. It's how much light is hitting each pixel and what's done with it on the way out. The new FF Nikon, as I've said in other posts, seems to do very well - and the pixels are crammed in there pretty tightly? So while I do understand...I agree that to get the same DOF at a given Fstop, the two formats are not equal. Good or Bad? depends. But I don't think in terms of total light hitting a sensor...since it can only hit a pixel at a time.

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