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Olympus' ISO
#1
http://www.duncanmartin.com/blog/2013/08...so-values/

 

which makes me feel that E-M5's lowest ISO 200 is already an extended ISO value (underexpose by 1 stop then boost it up)....I can't understand the strategy of Olympus.

 

It is strange why Olympus does not put the true native ISO 100 on the camera settings (E-P5 has ISO 100 but listed as an extended ISO) and make some extended low ISO values like 50. Lower ISOs are indeed very welcome on MFTs though at expenses of some DR when those extended low ISOs are used.

#2
I agree. Although I don't understand why a low base iso would reduce DR.

The Pentax K5 was perfect in this regard as it featured a native iso 80 which allowed it to provide the best DR of any other sensor at the time.

I'm really puzzled at Olympus and Panasonic in terms of base iso. If one system really needs low iso values it's definitely MFT. Why do they not feature a native base ISO of 50 or 80? That would allow us to use f1.4 and 1.8 lenses in bright day light. We are already being limited DOF wise, thus not being able to use these lenses wide open is a major downside of the system.
--Florent

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#3
Quote:If one system really needs low iso values it's definitely MFT. Why do they not feature a native base ISO of 50 or 80? 
 

I guess ISO 50-3200 doesn't sound as attractive as ISO 200-12800... But I agree that the former would be a more reasonable ISO-range for MFT. 

#4
As a vague generalisation with lots of assumptions I'm sure someone will argue over: Because of the smaller sensor it would start to show increased noise sooner than bigger sensors at a given nominal ISO setting. Thus to me it makes sense to optimise higher ISO performance. Low ISO performance just isn't generally a problem area.

Having a low enough ISO setting to use fast glass in bright light is less of a problem, as it can be easily worked around using a ND filter.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#5
Quote:Low ISO performance just isn't generally a problem area.
 

Calling it a problem area would probably be an overstatement, but the low ISO performance of MFT is still miles away from the cleanness of a full frame sensor (compare the E-M5 and the D4 for example). 

The question is: Does the E-M5 really need ISO 25600, when everything above 3200 is hardly usable anyway? Or would a sensor that is optimized for lower ISO be the better option in terms of image quality? I think the latter is true, but it's mainly a marketing issue... 

 

If you are happy with MFT results at ISO 200, then ND filters are indeed the solution to the problem  Smile
#6
Quote:Calling it a problem area would probably be an overstatement, but the low ISO performance of MFT is still miles away from the cleanness of a full frame sensor (compare the E-M5 and the D4 for example). 

The question is: Does the E-M5 really need ISO 25600, when everything above 3200 is hardly usable anyway? Or would a sensor that is optimized for lower ISO be the better option in terms of image quality? I think the latter is true, but it's mainly a marketing issue... 
 

Yes, exactly. There are at least two reasons for low ISOs to be essential for MFT cameras: (1) The image of a MFT camera at its native ISO is not as clean as that of a FF camera,due to the smaller size of the sensor. Even extended low ISOs can make the image cleaner. (2) In bright light conditions larger apertures are more often used than in the case of FF cameras, because of the larger DOF of MFTs.

 

If the DXO results are correct then the native ISO of the sensor in EM5 is 100. But Olympus choosed to drop the native ISO and start ISOs from the extended 200 in  the camera settings, which is strange.

#7
Quote:Having a low enough ISO setting to use fast glass in bright light is less of a problem, as it can be easily worked around using a ND filter.
 

I find the use of ND filters a real pain in the butt!

Between having to screw a filter every single time I need to use f/1.4 or f/1.8 and being able to dial ISO 80 at the touch of a button, there is simply a world of a difference in terms of convenience.

Plus, you need different filter sizes.  If the lighting changes, the filter may force you to bump the ISO which is not desirable or unscrew the filter....  It's just super annoying, plain and simple.

This is especially true when it could easily be otherwise if Oly or Panasonic had followed a route similar to what Pentax did with the K5.
--Florent

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#8
Ok, so I see two issues here:
1: Wanting a lower ISO to lower noise.
2: Wanting a lower ISO to use fast lenses in bright light without using accessories.

Even if very high ISO settings are not pretty when offered, I wonder if their choices still mean they're less noisy than they would have been if they optimised for low ISO instead?

For #2 above, would a faster shutter speed option be a desirable alternative? I've not kept up to date, but how fast do electronic shutters go these days on stills cameras?
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#9
Quote:Even if very high ISO settings are not pretty when offered, I wonder if their choices still mean they're less noisy than they would have been if they optimised for low ISO instead?
 

As far as I understand, a sensor has only one native ISO. All ISOs higher/lower than the native ISO are extended ISOs: they are obtained with softwares/firmwares. ISOs higher than the native ISOs are obtained by underexposing some number of stops then amplifying the brightness of the image with softwares to make the image have normal brightness; during the process noises are also amplified so extensive noise reduction is needed for high ISO images. ISOs lower than the native ISOs are obtained by overexposing a few (1-2) number of stops then de-amplifying the brightness of the image with softwares to make it have normal brightness; during this process the noise is de-amplified also so the image looks cleaner than that exposed at the native ISO.

 

Yes, even at the native ISO some amount of noise reduction is needed to make the image cleaner, but at extended higher ISOs additional noise reduction is needed, as far as I know. Extended low ISOs do not need additional noise reduction. The only problem with extended low ISOs is that in high contrast situations some highlight clipping may be caused.

 

 

 

Quote:For #2 above, would a faster shutter speed option be a desirable alternative? I've not kept up to date, but how fast do electronic shutters go these days on stills cameras?


A faster shutter speed is certainly desirable, but only a few exsiting MFT cameras offer a shutter speed up to 1/8000 sec, including the E-P5, E-PL5, GX7. Both the E-M5 and the GH3 offer a shutter speed only up to 1/4000 sec.
#10
Quote:A faster shutter speed is certainly desirable, but only a few exsiting MFT cameras offer a shutter speed up to 1/8000 sec, including the E-P5, E-PL5, GX7. Both the E-M5 and the GH3 offer a shutter speed only up to 1/4000 sec.
 

 

This is not quite right.

Only two MFT bodies feature a 1/8000 sec. shutter speed: the Olympus E-P5 and the Panasonic GX7.

All other bodies top out at 1/4000, including the OM-D, E-PL5 and GH3.
--Florent

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