Nikon D800E and Olympus OM-D

No, I´m not going to use both D800E and OM-D. This was just one of my reality checks. It is nice to check every now and then what´s going on with various brands and systems. I did not want have the subject as D800E versus OM-D because this also is not about that. There is no single camera of which I could say that it is made for me. There are a few cameras I could be perfectly happy with, if there were no other choices. Both of these two overlap my needs but differently, and I wanted to know to what extent and how differently.

Size matters

One of obvious differencies between these cameras is physical size and weight. The image above shows them with lenses which give (almost) equal angles of view: Nikon 35mm f/1.4 G AF-S and Olympus M.Zuiko Digital 17mm f/1.8. Both are the best native "35mm" prime lenses from respective brands for these bodies. 

The difference by 2X for focal lengths in these lenses shows that there is also the same difference between image size on sensor. The area of OM-D sensor is roughly one quarter of D800E sensor size. Respective sensor sizes in pixels are 6144 x 4912 pixels for Nikon (36 megapixels) Nikon and 4608 x 3456 pixels (16MP) for Olympus. Sensors have different aspect ratios, 3:2 for Nikon and 4:3 for Olympus. Because of different aspect ratios final images are cropped a bit differently and actual resolutions are dependent on this cropping. I would say that D800E has roughly 37% more linear resolution to start with when compared to OM-D. True relationship with image quality is dependent on many factors including filters on sensor, the lens and of course users´s shooting and post-processing technique.

Handling

I have used Nikon FF DSLRs long enough to be happy with D800E from the start. There´s "nothing" to it. It´s just like a Nikon should be. Olympus OM-D has become pretty much an extension of my right hand. D800E couldn´t become so much used because of weight and size. For me this is the difference, not handling as such but size and weight. Every extra lens makes the disparity only more favorable for OM-D.

This is the situation now. If I were still an advertising photographer I would go for more resolution and Nikon´s excellent 85mm PC-E lens. Nikon has also better AF tracking, but I don´t need it.

Camera Body Tests

I have tested and written about OM-D. Others like dpreview.com or dxomark.com have tested both. I will not go any deeper into that territory here, just refer to a couple of measurements later when they mean something.

Key West, Florida, USA, 2013. OM-D w. 17mm f/1.8 lens

Camera-with-Lens Performance

This is what I´m interested in. Final image quality with RAW images opened in latest Lightroom.

I posted in January a blog on diffraction. There D800E was my example for two reason: diffraction is easy to see because of huge resolution but also it is not such a problem as common "wisdom" says. I´m not going to duplicate those crops from image center here.

Here is my test targets as shot with D800E:

I shot the same with OM-D so that the subject ie. those targets take the same area of frame. Lets compare what happens in corner targets, which are far from extreme corners. 

Above is D800E 35mm at f/8 and below OM-D 17mm at f/4. Nikon D800E crop is 100% and OM-D crop has been enlarged to the same size. Why these apertures? Because that´s my most used depth of field and DOFs are equal when D800E is closed down two steps more than OM-D.

Now, check Nikon 35mm center performance in my previous post. The difference is quite obvious to what is seen here with Nikon 35mm lens. Even here D800E crop is slightly sharper or should I say cleaner than the enlarged OM-D crop but the difference is neglible for any practical need. There is a test of Nikon 35mm f/1.4 G lens at photozone.de. They tested with Nikon D3x. D800E only amplifies the difference between center and corner performance.

In this example ISOs are at 100 for Nikon and 200 for Olympus, these are studio shots on tripod. I shoot normally hand held. To keep shutter speeds the same I would need then to raise my ISO for Nikon to 800 if OM-D is at 200 in order to have same DOF. Actually this would not be a problem for Nikon in this kind of situation. ISO 800 suffers only slightly. The difference is even not worth producing here. What happens though is that D800E loses it´s lead in dynamic range, which can´t be seen with this kind of target. According to dxomark.com these two cameras would have practically the same dynamic range at ISO 200/800 setup. The same is true for tonal range and color sensitivity. The only real difference between these cameras with these lenses would be resolution in the center of frame. (Structures in grayscale is not sensor noise, this structure comes from printed target). 

Key West, Florida, USA, 2013. OM-D w. 17mm f/1.8 lens

In Print

I prepared print size files for you to print and see. Nikon crops are from the center of frame and, lazy as I am, OM-D crop is the same off-center as above. M.Zuiko 17mm has quite even performance over the frame. In print size A3 there is no visible difference in print between images or test target from these two cameras.

Also size A2 prints are quite similar with normal everyday subject, but with this kind of target the higher resolution of D800E (above) can just possibly be seen on glossy paper. It depends on printer, paper etc. Make a 6 by 6.1 cm and 300 ppi background in Photoshop. Copy and drop the above crop from A2 print file into it. Print with your printer. Any difference?

This is an image file for a crop from A1 print. Make a 6 by 8,7 cm and 300 ppi background in Photoshop. Copy and drop the above image file into it. Print with your printer. Any difference?

Real Life

Pixel peeping on screen and reading numbers on some test sites is easy. Knowing what matters in real life and what doesn´t (and how much or how little) is a lot harder. These examples above show that the absolutes are not valid in real life, and these examples are still far from real life and in favor of the one which has the better starting point.

In real life hand held photography there is one more thing which forces these cameras closer to each other. It is in-body image stabilization (IBIS) which OM-D has.

What we have here is again D800E above and OM-D below, but this time I´m shooting hand held in a dim light. Exposure for OM-D is 1/13 s at f/4 and ISO 200 with IBIS on. I can get sharp images with a ratio of 9/10. To get sharp images with D800E, I had to set shutter speed at 1/30 s at f/8 and raise ISO accordingly to 2000. Now my test gave me sharp images with a ratio of 3/10. Sharp and sharp... Well, this is what I get at these parameters. This goes to show the power of IBIS. Besides of sharpness there are other things to consider, at ISO 2000 D800E has fallen below OM-D in dynamic range and color accuracy. IBIS keeps you going within the sweet spot of OM-D for a long time.

Miami Beach, Florida, USA, 2013. OM-D w. 17mm f/1.8 lens

Summary

Technically, if you are striving for the most detailed images, Nikon D800E is far better than OM-D. It has more resolution, wider dynamic range and higher color accuracy. But then also you must be up to task because this goodness does not come for free for the careless shooter. You must use tripod, you must use only the best lenses inside their best performance envelope. Small things mean suddenly a lot if you want keep the performance up. On the other hand D800E has plenty. You can give away a lot and still get great images.

My D800 pluses compared to OM-D

- lots of resolution, dynamic range and color accuracy to start with

- better viewfinder in bright daylight

- possibility to have shorter DOF

My OM-D pluses compared to D800E

- size and weight

- IBIS helps keeping ISO low and dynamic range up

- better exposure metering (ETTR) with a practical gain of at least 1EV in DR 

If I were a hardcore dedicated landscape photographer or still an advertising photographer, I would take D800E. While I am not, D800E does not give me anything above OM-D in practical shooting and in my print range of A3 to A1. It would not make my images any worse either. It only is bigger and heavier and it would strip me from many shooting opportunities which a smaller system gives just by being smaller and handier to have with me.

-p-

Being Diffraction Limited

Luckily this subject makes no dramatic screen play even though some writings about it in the internet make it seem so.

First of all: what is diffraction? Wikipedia explains it quite thoroughly. Please read there and look at animated examples. To explain how light works, light must be partly explained as waves and partly as tiny particles, photons. Light is counted as photons in camera´s image sensor. Light behaves like waves when it interacts with the diaphragm inside lens. Common sense would say that tiny particles would either go straight through the slit or hit it and bounce off. Common sense is wrong, diaphragm is a slit which makes light waves bend and causes diffraction. Actually the whole lens and/or every single lens element of the lenses causes diffraction but the smallest opening is the most important. The smaller the opening the more we have diffraction. This makes the diaphragm the major culprit in most cases. 

Wikipedia shows how diffraction (see Airy disk) is directly dependent on the wavelength of light and the f-number used. The bigger the f-number the smaller the aperture and the more diffraction. The longer the wavelength (ie redder light) the more diffraction. In spectrum the opposite short wavelength end is blue and causes least diffraction. In the middle we have yellow-green.

Wikipedia shows lots of equations but in practical photography you need only remember those two: aperture and color of light. Red spreads more than blue. And the fact that diffraction is a property of every lens.

Diffraction limited bodies?

In the internet there are furious debates on camera bodies being diffraction dependent or diffraction limited. How come when diffraction is property of the lens? This an issue which has risen when megapixel counts get bigger. The more megapixels in a sensor the smaller the sensor elements are. Well actually it is the opposite: we get more megapixels with smaller sensor elements, sensels or pixels, if you want. We have long ago passed the point when Airy disk can cover several sensels. Lets say we have two very small light sources side by side. They can´t be seen as two on sensor if those Airy patterns overlap enough. Two becomes first a rod with two blobs at the ends and then with even smaller apertures those blobs grow together. No resolution left, more pixels inside that blob does not help.

The theory of diffraction alarmists is that more megapixels is bad because diffraction is seen at ever larger apertures and this will make such cameras useless for most of photography. It was long ago when I mentioned to bosses at Canon that sensors are coming eventually diffraction limited. My point was that in commercial photography, like in table tops or product shoots, we need to use small apertures to get enough depth of field. They must make sure that the gain in sensor resolution and increasing bit depth does not cause problems here. The answer was that there is no such thing as a sensor being diffraction limited, never heard of. Oh well...

An example of diffraction

There are hundreds of blogs and thousands of discussions on Nikon D800 and how it is diffraction limited. "You should not use smaller aperture than..." Yes, Nikon D800 is a good example to bring something tangible into this discussion, which now becomes one of those hundreds and thousands. Actually I wanted to test Nikon D800E and its 36 MP sensor just to see how good it really is. It was sort of reality test to see where things are going. As a sidekick we can check these Nikon D800E test images as an example on how diffraction works:

f/1.4

f/2.0

f/2.8

f/4.0

f/5.6

f/8.0

f/11

f/16

Looking at the series above you can see how they get sharper up to f/4.0 and then start to get softer after f/5.6. I really can´t pick the better one from f/4.0 and f/5.6. Now, diffraction is there all the time, but it is not the only working parameter in optics. Other gains make the image better when diaphragm closes down untill diffraction becomes too strong. I have prepared these examples so that lightest areas are the same in all images. By doing so diffraction eats from dark areas and you can see how black lines get weaker. I could correct a lot of it in postprocessing but I wanted to show how diffraction works. These crops are 100% and from the center of image. The lens here is the relatively new Nikon 35mm f/1.4 G AF-S. The pattern seen in people silhouettes is moiré. Nikon D800E is the second camera I have tested which is able to show it. The first was my PhaseOne P45+ digital back with the better Mamiya 645 lenses. This combination is so good that you can see this moiré pattern even wide open. Why am I speaking about moiré as a good sign? It is because those areas are printed with a very tight raster. Only the sharpest lenses and sensors can see that there is a pattern. D800E can´t resolve the pattern itself yet, no one-shot consumer camera can from my shooting distance. By f/16 the lens can not convey even a hint of this pattern to sensor because Airy patterns overlap so strongly.

Being Diffraction Limited

To get a better idea how deeply (or not) D800 is diffraction limited is to compare it to D700, which has 12 megapixels. They both have a full 35mm size sensor, which means that D700 has bigger sensor elements and it should not be as much diffraction limited as D800. Right?

This comparison image shows D800E above and D700 below. Aperture is at f/5.6 to be on the safe side for D700. Again D800E is at native 100% and I have enlarged D700 image to same size by using Photoshop Bicubic Smoother interpolation. This is pretty much what happens if you want to print a D700 image as large as a D800E image. Well, this tells us only that D800E has more pixels and this lens can show it. How ever, the difference is not coming from megapixels alone as D700 has in front of sensor a low pass filter which softens images while D800E doesn´t. (Actually also D800E has a certain layer structure because of which this could be argued, but it really is of no concern here.)

Same situation, but now my aperture was at f/16. To give D700 a slight advantage I have corrected its contrast, but even then there´s no question which camera shows more detail. It is easy to see that D700 has not suffered as much from diffraction, it is not as much diffraction limited. But this is only because D700 is more limited to start with. Diffraction is a relative thing, it is a gradual thing. There is no Diffraction Limit™ which hits your images and makes them suddenly unusable. But there also is no superhero called Diffraction Buster. You have learn to live with diffraction, and preferably, learn to correct what it smudges in post process when you need to close down because of need for DOF.

Rules of thumb

When you think about image quality you should always think about the combination of lens and body. As a simplification (image quality) = (lens quality) * (body quality). Body quality meaning sensor plus conversion to final image. Here the lens quality must drop dramatically before the difference between these bodies becomes obscured. As a rule of thumb we could say that diffraction starts to show in images when you have closed aperture down a full stop from the size (number) of pixel pitch. Nikon D800 sensor´s pixel pitch is 4.88 µm. This tells us that we can go beyond f/5.6 to almost f/8, just like is seen above. And then again we must remember that diffraction is caused by the lens. With slower lenses, like a zoom having f/5.6 as largest aperture, image quality usually gets only better when stopped down by one stop. But there are also lenses, especially with P&S cameras, which should always be used wide open, if you think only about image quality as seen here. Know your equipment!

I will come back to D800E and discuss OM-D with it in a later blog.     

-p-