Although photographic digital cameras are present in pictorial photography from only about twenty years ago, changes in their design, features and performance have been quickly applied in a non-stop run. Nowadays, the popularization of SLR (Single Lens Reflex) bodies based in the XX Century classic designs are being confronted to some new bodies named as MILC (short for Mirror-less Interchangeable Lens Camera), EVIL (short for Electronic Viewfinder Interchangeable Lens) and some other combined acronyms. The main advantage of the classic SLR camera bodies is the ability to show in the viewfinder an image coming directly from the taking lens and in this manner, to avoid the framing parallax errors. Nevertheless, this design carries a problem. Being the necessary mirror box of a fixed and unavoidable dimensions, it compromises the design of the lens, specially for short focal length ones. Having the digital cameras a sensor as a registering device, it was obvious that the next step in evolution would be the use of the image captured by the sensor as an image to be shown in an electronic viewfinder. This shares with the SLR the parallax error elimination and encompasses a better framing vision for low light conditions, almost independent of the maximum lens aperture in use. Additionally, the elimination of the mirror box, allows for a shorter flange focal distance, favouring the lens design.
Some electronic problems have caused that EVIL cameras haven’t been common for the high-end level until the last years. Even today, in a market with models from Fujifilm, Olympus, Sigma, Sony, Panasonic, Pentax, and many others, there is still the discussion about its reliability in replacing the classic SLR bodies from Canon and Nikon in the professional segment. As any other technical consideration in Photography, the suitability of such a decision must be related to a given purpose. Although the same camera bodies and the corresponding lenses are used for a large number of photographers, not all of them use the gear for the same kind of photography, nor aiming for the same final image quality level. Therefore, any performance analysis would be targeted to a well defined photographic application. Keeping that in mind, I will try to develop a comparison between my former Nikon SLR equipment and the recently acquired Sony Alpha 7II, paying attention to my concrete needs and to the way I consider the practice of Photography.
My main and almost exclusive style to take pictures is landscape, both natural and urban. The majority of my pictures are taken keeping in mind a final monochromatic version as inkjet printings on high-quality paper, photogravure on copperplate and recently, as palladiotypes. Almost 95% of my pictures are taken from a tripod standing camera. To do that and during the last twelve years, I have been evolving from a Nikon D70 (6million pixels APS sensor) to a Nikon D700 (12million pixels full frame sensor) and for the last four years to a Nikon D610 (24million pixels full frame sensor). My usual printing sizes can be well achieved with 12million pixels, being the 24million pixels of my last body a surplus helping in some needs for occasional re-framing.
All those bodies have been combined with five lenses. A Nikkor Zoom 18-70mm AF (only for the D70 body) and a series of 24, 35, 55 and 135mm of fixed focal length for the two full frame bodies (D700 and D610). All those lenses come from my old film Nikon camera bodies and are models acquired in the seventies and eighties of the past century. Excepting the 18-70mm zoom, they are all manual focus lenses. Looking at work of the past five years, the most frequently used lens were the 24mm and the 55mm, taking this last over 75% of my pictures. With all these data on the table, I decided to look at the market aiming to reduce the backpack content. Time goes by and weight is more and more annoying (Fig., 1).
The recently appeared mirror-less and EVIL cameras, with the capability to interchangeable lenses, compactness, lightweight and some new electronic controls, seemed to be an option to consider. Combining the necessary contention of budget and the need to preserve the use of a full frame sensor, the offer is quite reduced. After compare specifications, I have been decided by the Alpha 7 series from Sony. At this moment, the market offers the Alpha 7, the Alpha 7II, the Alpha 7S and the Alpha 7R. I discarded the 7R because of its 36.4million pixels sensor. I don’t need such a high number of pixels and they slow down the processing in the computer. Additionally, my work is based in an extended depth of field and so tiny pixels are greatly affected by the lens diffraction at very closed aperture values. The Alpha 7S model incorporates a sensor of 12million pixels (like my former Nikon D700) and its features are preferentially driven to the motion picture. Finally, between the Alpha 7 and the Alpha 7II the election is easy. They are almost the same camera with the same sensor of 24million pixels (like my current Nikon D610), but the Alpha 7II comes with some improvements. Perhaps the most relevant is the so called Steady Shot, that helps in hand held shootings.
Then, my new toy is the Sony Alpha 7II equipped with the kit lens Sony Zoom FE f/3.5 – f/5.6, 28 – 70mm OSS. Beside this basic kit, I acquired the bayonet converter ring XPAN-S/E from KIPON. It allows the attachment of former Hasselblad XPan lenses to the E-Mount from Sony. The idea is to use my former Hasselblad XPan 45mm f/4 lens (Fig., 2). As with all my camera bodies, an L-Braket to attach the camera to the tripod completes the set. As always that I incorporate a new camera and/or lens, I perform some trials in order to know how to achieve the same image quality level and usability comfort at which I’m used with the former equipment. It is not so important to establish a competition between cameras and lenses, but to acquire a knowledge of the equipment and digital image processing that can help to take advantage of its characteristics. This is the main scope of this post.
Beyond the necessary adaptation to the camera menus, buttons and associated functions, the assays performed are as follows:
- Testing the Sony Zoom lens performance reproducing a suitable test target at all the diaphragm apertures available and selecting a focal length closer to the most used in my work. In order to compare with the above mentioned Hasselblad 45mm f/4 lens, this is the chosen focal length.
- Testing the Hasselblad 45mm lens performance reproducing a suitable test target at all the diaphragm apertures available.
- Measurement of the system MTF at the center and the corner of the image field with the Sony Zoom lens at all the diaphragm apertures available and a focal length of 45mm selected.
- Measurement of the system MTF at the center and the corner of the field with the 45mm Hasselblad lens also at all the diaphragm apertures available.
- Measurement of the Sony Alpha 7II OECF (short for Opto-Electronic Conversion Function) and Dynamic Range (DR). Comparison with the same data from my former Nikon D610.
The lens testing is combined with the capabilities offered by the Photoshop plug in to process raw files, the Adobe Camera Raw (ACR). The images obtained from the Sony Zoom lens were corrected applying the Lens Profile available in the ACR data base. Those coming from the Hasselblad lens were corrected with the manual tools available in the same ACR. The system MTF is measured taking an image of an slanted edge, both at the center and in a corner of the field, and measuring the results with the plug in SE_MTF_2xNyquist available to run in the so called ImageJ digital image processing software. The theory involving the measurement of the system MTF in photographic cameras and the use of the mentioned plug in for ImageJ can be found in this post.
All these tests generate a lot of results that can be analysed and compared in many different ways. I will show those I consider most relevant and remember that I’m always concerned by monochrome landscape as the main camera application. For instance, a poor lens performance at wide open diaphragm is nothing especially important in my case, because I’m almost always looking for an extended depth of field. Conversely, knowing how early the diffraction effects are visible in the picture quality is a very important data for photographers working almost always at very closed apertures. Find below the graphs and comments about all that.
About the aspects of usability, it is necessary a period of time to be confident with such a light camera. Although that using the same tripod than with the Nikon equipment, the respective weight relationship favours a better steady set, the first times do you take the camera out from the backpack, is not so easy to avoid a feeling of mistrust. Conversely, when the camera is at hand, buttons, commands and zoom ring are well designed and immediately give a sense of security. With the camera in a too high or too low position, the tilting rear screen is a luxury as a substitute of the Nikon right angle viewfinder.
Moreover, the electronic viewfinder is also of great importance specially in low light situations. No more problems of focus or doubts in depth of field into the forest in an overcast day. Even in Manual Focus mode, with the Hasselblad XPan lens, the Focus assistant highlighting in red the object edges is a great aid. Following with the focus aids, all the focus area modes in the Sony Alpha 7II reach any position all over the full frame area. This a great improvement respective to the Nikon SLR bodies having the AF module restricted to a central area more or less coincident with the APS format. In this way, I can come back to the old sequence of actions in the process of taking a picture with no other distractions that the picture I want to take:
- Walking around without camera looking for a subject, a magic awareness moment, a surprise or any other kind of feeling.
- When something appeals me, is time to look for the better place from where to take the picture. Distance, heigh and lateral displacement in order to better combine the subjects relationships into the scene (terrain and/or physical constrains play sometimes also their role!). Then, placing the tripod in this site and mounting the camera on top.
- Adjusting the correct lens or the zoom setting to frame the scene.
- Looking for the needs of depth of field and adjusting the correct aperture value. Eventually, evaluating the need for a series of frames with differential focus to be merged by a focus stacking technique.
- Adjusting the self-timer at 2sec delay. Then, the intense moment of pressing the shutter.
As a synthesis, technology evolves. It offers new and amazing tools. Photographers should too evolve in their way to consider their tools and the way to face to the photographic act. A little better performance linked to a compact and lightweight bulk, would mean better opportunities to live a lot of intense moments.