Guest Post By: Cemal Sagnak

With the Launch of the Sony A7s the company is offering 3 almost identical  Cameras with a different Sensor design for matching Customer needs. This is unique and brings the Consumer into the conflict selecting from 3 Full Frame sensors to match his personal need. You can select between the resolution King A7r with 36mp and the moderate and affordable A7 with 24mp or the new Low Light Monster A7s.

It’s a clear trend driven by the technology leaders Nikon and Sony to launch Cameras which became “night vision devices”. Maybe it’s a Trend requested by the Users but maybe, “because they can”.

After a strong trend towards increasing megapixel the trend goes to achieve higher image quality by downsizing to enhance the low-light capability on the cost of resolution.

Low Light Monster Hitting The Mainstream

We had those cameras for years in the professional segment like the Nikon D4 with 16MP. The latest Innovation by Nikon used  a slightly modified sensor and more affordable Retro Body called Nikon Df. Many expected it with a 24 MP sensor but came out with “only” 16 MP , a resolution which is more common in APSC than in Full Frame Cameras.For a while it was the King of the night until the new “Lord of the darkness”, the Sony A7s with just 12 MP was launched. I followed the initial reaction by claiming the 12 MP is not state of the Technology today, but what is the state of the Technology ,or better say the state of the Art and how many pixel does someone really need.

Size Matters

Decreasing the amount of pixels, allows manufacturer to build larger photosites which are better capable of capturing light.

Let’s do some maths and just a little physics. When we compare size and megapixel , an APS-C with 16 MP Camera would have similar sized of Pixel as compared to a FF Sensor with 36 megapixel. Now taking this to the next level would mean you are more than doubling the pixel size if you have 16 MP on a FF camera , and even bigger with the Sony A7s.

Pixelsize comparison :

Nikon D4  -  7.3µ

D800  -  4.9µ

Nikon D7000  -  4.8µ

Sony RX100  -  2.4µ

Sony A7s  -  8.4µ

When comparing image sensors, either CCD or CMOS, the system is essentially a box where the input is light and the output is an image based on the light that is seen. The service provided by the sensor is the conversion of light to a digital image measuring light energy. And here hits physical limitations the abilities. Increasing the count of the pixel does not increase the measureable light. In other words: The larger the size of a pixel the better the ability catching (available) light (and the dynamic range).

Sony´s engineers confirms this physical fact, when they were asked why to put a 20.2 MP sensor into the relatively small 1” sensor of RX100 :

“It’s true that increasing pixel count increases noise. But since we manufacture our own sensors, we can easily tweak sensor specs to suit specific needs…..”

Knowing the correlation between Pixel count and Sensor size I reviewed my archives to find high Iso images when having the Nikon Df for a period of time.

There were some occasions like in the church or shooting night shots, but statistically I shot maybe 20 pictures out of 3000 with ISO higher than 3200.

I have to admit shooting with ISO 12800 is a nice feature to have but its like taking a sledgehammer to crack a nut. Some might need it but I am a streetshooter and I am okay with max ISO 1600.

The Leica M240 has a better lowlight capability than its predecessor the Leica M9 and in fact I was much more relaxed using Auto ISO on the M240 than with other Leica cameras, For me it has a perfect balance between high resolution and low Light capability. Having said that, my Preference Camera is and will stay the Leica M9. Its look and apeal is the closest thing to analog Film, in fact when Leica designed the M9 in cooperation with Kodak, analog Film stand model for the KODAK KAF-18500 Image Sensor.

Printing with Low Pixel Counts

Most Print Services require a quality of 120 dpi to get good to very good printing quality.

Here an example :

A uncropped file from a Leica M8 with 10 MP (3916 × 2634) can be printed :

• in a good quality with (111 dpi) on 70×90 cm
• very good quality with 166 dpi on 50×60 cm

In this case the pixel count makes a difference but looking into the size of prints you can get with a 16.2 MP file is maybe larger you might need. Don’t get confused by your home printer with +1000 dpi, this number represents overprinting a single “dot” with different colors to create the color that is needed.

Dynamic Range

One additional advantage, and maybe for me the biggest advantage of modern Low-Light Monsters is the Dynamic Range.Simply said its the ratio between lightest and darkest regions (contrast Ratio). The ranges increases with the size of photosites of each Pixel. Actually the human eye has a very wide DR as it can easily adapt to different light situations. the DR of a Human eye is seen in the range of 24 f. The Sony A7s shines also here where the dynamic range is measured similar to the high END Video Cameras , one which is used in professional and cinematic Genres. In this area a high DR is critical capturing night and dark Scenes.As long you are not planning to become the next Steven Spielberg this topic is less important for you.

CONCLUSION

Here is my conclusion doing my math and research, I personally don’t need a “Lord of the darkness” as I really prefer some grainy look on available light photography but I can also live very well with lower pixel count in a FF sensor and would only decide for the A7s because of its dynamic range. The perfectly balanced Camera for me is the Leica M240. But thats just my personal choice. The A7r is demanding regarding lens selection and its size of the files. The Sony A7 has the same MP vs Sensor size ratio as the M240 still performs less good on high ISO. But A7 has a great image quality and the best performance / price ratio as its the only FF camera hitting the 1000 Euro line. As I don’t shoot DSLR anymore the Nikon Df is not an option for me but delivers one the best IQ and dynamic range.

Thanks for reading.

Cemal Sagnak - http://cemalsagnak.wordpress.com/