Another Olympus E-M1 and SONY a7 walkabout test, high ISO

Started Jan 29, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Thanks for the truth!

Daniel Wee wrote:

So, let me see if I can summarize some of what I understand from this debate:-

IF the following conditions are true:-

a) your mFT glass is 1-stop faster than your FF glass
b) you want to preserve the same DoF
c) you want to preserve the same shutter speed

THEN you will be able to shoot at 1-stop ISO advantage over the FF camera. For instance - mFT ISO 1600 0.8 sec @F1.4 vs. FF ISO 3200 0.8 sec @F2.8

Not quite.

First, the speed of the MFT lens versus the FF lens just determines the baseline where DoF can be set equal. The comparison can be made regardless of how the speed of the two lenses compare.

Second, shutter speed is not really to be thought of as something you want to preserve. Rather, in practical applications, you usually need a certain shutter speed to reach your objectives. Stabilization systems aside, the speed you need to meet your objectives is the same for any given scene and AoV. It is therefore held constant for the purpose of comparisons between systems.

Third, the equivalent settings would be f/1.4 and 0.8 s at ISO 800 (rather than ISO 1600) for MFT and f/2.8 and 0.8 s at ISO 3200 for FF. With your proposed settings, the MFT image would be brighter (with default jpeg conversion) and have higher RAW values. Whether this matters or not depends on how close you are to the highlight clipping point.

On the other hand, IF the following conditions are true:-

a) you want to preserve the same DoF
b1) you don't care to preserve the same shutter speed

OR b2) your mFT glass is not 1-stop faster than the FF glass

OR b3) you are prepared to down-sample the FF image to the mFT size

THEN the above stated advantage no longer holds.

Not quite. With respect to b1) and b2), see my remarks above. With respect to b3), we usually assume that the pixel count is kept constant in comparisons of signal-noise performance. So no, the ability to use a two-stop lower ISO at the same DoF does not depend on these conditions.

In terms of shooting for same DoF AND same shutter speed (something I personally don't worry too much about), you'd have something like the following two images:-

a7 ISO 3200, 0.8 sec @F8

E-M1 ISO 1600, 0.8 sec @F4

While by no means comprehensive or scientific, based on these two images, I would conclude, based on visual inspection, that:-

a) the a7 noise at ISO3200 is marginally less than the E-M1 noise at ISO1600
b) this advantage is even more pronounced when we downsample the a7 image to the same size as the E-M1

Both images strike me as noisier than I would normally expect them to be. That my be due to the way they are processed (according to your OP, you kept luminance NR at zero but there's more to noise appearance than that). The E-M1 image is also brighter than the A7 image, which of course affects the comparison.

We can get a somewhat clearer view by comparing the crops from IR test images below, pitting the E-M5 at ISO 1600 against the Nikon D800 at ISO 6400 (the D800 sensor performance being pretty much a carbon copy of the A7R sensor performance; it's probably the same sensor). The E-M5 does not reach quite the same DR as the E-M1 in DxO tests (there's about a 0.5 EV difference) but you can see the tendency anyway.

The crops are directly out of LR 4.2 with the E-M5 images upsampled to match the pixel count of the D800. All settings at default except as indicated in the captions. Click on "view original size" to view them properly. As I think you can see, the E-M5 does better with regard to signal-noise performance.

Nikon D800 at ISO 6400, no NR

E-M5 at ISO 1600, no NR

Nikon D800 at ISO 6400, chroma NR at default (25), no luminance NR

E-M5 at ISO 1600, chroma NR at default (25), no luminance NR

Nikon D800 at ISO 6400, chroma NR at default (25), luminance NR at 50

E-M5 at ISO 1600, chroma NR at default (25), luminance NR at 50

I usually shoot in aperture priority because I want to get the lowest DoF possible. Not always, but this is a personal preference. Furthermore, I like the CZ 55mm F1.8 but don't have any glass that can do F0.9 for mFT in my arsenal. Certainly none that will AF. Since I don't print, downsampling seems to be the norm when used with many web applications.

Therefore, for people who shoot like me, for whom:-

a) shallow DoF is a priority

If you frequently want more shallow DoF than a fast prime on MFT can provide, then it is indeed a good idea to go FF. I don't, which is one reason why I shoot MFT. As to the samples in your OP, the FF image in your first, second, fourth and fifth pair have too little DoF based on my preferences. In the third pair, the MFT image is misfocused and in the last, DoF is irrelevant.

In other words, I normally don't need more "DoF control" than MFT can provide. However, I want more "FL control" than FF can provide (more lenses in my bag rather than in a drawer back home). Consequently, for my shooting, I get more of the versatility I want from MFT than from FF.

b) maintaining the exact same shutter speed is not a priority

See above.

c) downsampling is always an option

See above.

The advantages of E-M1 over the a7 stated in this debate would lose some of their relevance. Furthermore, even if the conditions were met where the E-M1 could shoot at a stop better than the a7, there doesn't seem to be that much of an advantage noise-wise, judging from the samples above. Lastly, the a7 can go as low as ISO 50 so where shutter speed is not a constraining factor, there are more advantages that can potentially be realized, just as IBIS affords other potential advantages for the E-M1 in other situations.

When you need better signal-noise performance than an MFT camera can provide at base ISO, you simply bracket exposure and then merge and align (as you usually can when shutter speed is not a constraining factor). A couple of examples here. Both have more DR than any current FF camera can provide in a single shot.

So while I really love my E-M1 and its lenses, I think that in all fairness, for users who share my preferences and style, the noise advantage of the FF a7 is quite evident.

If you want more shallow DoF than MFT can provide with a fast prime, then FF has a signal-noise advantage, yes. If not, then it is the other way around.

I can also see that where the E-M1 has some real advantages is when you want the fastest shutter speed possible for a given DoF (and noise level). That said, for general usage, most of these issues don't come to mind - we just do whatever we need to go get the shot.

These are issues that we'd want to consider when deciding which system to get and what lenses to get with it. Then we don't have to fight with the odds against us when trying to get the shots we want.

So, hopefully, this is a fair summary of the debate as it relates to general usage - each tool for it's job.

Perhaps it's at least as important to match the tool to the photographer as to the job. As shown by this as well as many other threads, photographic objectives and preferences do vary between photographers.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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