Oly OMD-EM-1 vs. Fuji XT-1: an humble comparison

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Sebastien Guyader
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Oly OMD-EM-1 vs. Fuji XT-1: an humble comparison
5 months ago

Hello,

First, let me start with a disclaimer: I currently own a Pentax SLR (K10D) and have never used Olympus nor Fuji cameras. So I'm no fanboy of any of those two latter brands.

As I'm currently thinking about changing my camera, I've been interested in the mirroless systems, and impressed by the characteristics of both the OD-EM-1 and the XT-1. I have hard times to make my mind on which one I would buy. So, I've tried to read as much reviews/previews, and look at as many images taken by both cameras as I could.

Today the first studio shots for the XT-1 review have been released here on DP Review, so I immediately jumped to compare both cameras. Like many people, I think, I'm interested in high-ISO performance, particularly since these slightly smaller cameras can be used for day-to-day family / events photography, for which you may encounter low light conditions and don't have/want to use a flash. Hence, I soon compared the ISO 6400 shots from OMD-EM-1 and XT-1. Okay, I know that from the shutter speed recorded in EXIF data, it looks like the Fuji camera overestimates its real ISO by almost 1 stop, but anymways I found it would be worth doing some pixel peeping. As a RAW shooter, I looked at the RAW images on the DP Review comparison page.

The first thing that caught my eyes was how bad the RAW images from the OMD-EM-1 was plenty of color noise smeering the details, and some bad moiré. In comparison, the XT-1 image has almost no noise at all (maybe not enough when pixel peeping, but this gives the image a nice clean look).

I found it strange that the OMD-EM-1 behaved not as good as I expected. I was wondering if the RAW conversion could be possibly the culprit, and if a better RAW processing could improve the quality of the Olympus image. So, what I did was to download the RAW file from DP Review, in order to process it with my favourite RAW processing tool, the open-source program Photivo. Potivo is based on dcraw for decoding RAW data, and offers a good selection of demosaicing algorithms (but unfortunately not for X-Trans sensors yet). To convert the RAW file, I did basic things:

- demosaicing done with the "DCB sharp" algorithm (gave the best resolution with least moiré and artifacts)

- white point adjustment (down to 1000 from 4096)

- slight sigmoidal contrast adjustment

- and optionally for a second comparison, slight color noise reduction in LAB (all in Photivo)

- save as jpeg 100% quality, 4:2:2.

No sharpening, no luma noise reduction, no white balance adjustment...

I then compared a 100% crop region from this processed image with the same region from the XT-1 image (jpeg downloaded from DP Review, as Photivo doesn't decode the XT-1 RAW yet).

Here's a first comparison : 100% crops, not resized:

Left and right crops are from ACR-processed JPGs downloaded directly from DP Review. Center image is JPG processed in Photivo (see above for processing options, no noise reduction) from RAW file downloaded from DP Review

Here's the same comparison, but with some color denoising applied in Photivo on the Olympus RAW file:

Last, a comparison with the OMD-EM-1 crops scaled down to the XT-1 size:

The first thing one can notice is how much better the Photivo processed OMD-EM-1 image is compared with the ACR processed one from DP review. I don't know why ACR is so bad.

The second thing I can say is that for ISO 6400, when processed correctly one can retrieve a fairly good amount of detail from the OMD-EM-1 RAW file, albeit with more noise than for the XT-1 (though, remember that the XT-1 ISO is actually closer to 3200 as a result of the Fuji overestimation of ISO sensitivity). It's a pretty good result for a micro four-third sensor, I think.

Lastly, when pixel peeping in the left part of the crops (look at the floor in the BW drawing), it seems to me that the vertical and horizontal edges are as well (or maybe more) resolved on the OMD-EM-1, but the diagonal edges are better preserved in the XT-1.

As a sort of personal conclusion, I'd say that dispite it's smaller sensor, the OMD-EM-1 resolves almost as much detail as the APS-sized XT-1, and it's even impressive when you know that the RAW file is compressed to half the size of that of the XT-1. But is the Fuji camera reducing noise in camera, to render images taht are so smooth?

-Sebastien

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