A 35mm-like Medium Format Camera
By: Efraín García and Rubén Osuna
Editors Note: English is not the native language of this article's authors. While I have attempted to correct some of the more obvious linguistic difference, doing more than that would have resulted in a complete re-write, which would have substantially changed the flavour of the original.
In this article we will provide additional insights to those found in a previous review on this site, written by Eduard de Kam. Another interesting reading was also published here by Michael Reichmann himself. At this moment, very few alternative reviews are available on the Internet.
A diversity of systems cohabitated in the studios of professional photographers during the film days. Then, a Nikon 35mm set of cameras and lenses and a medium format (645 or 6x6) system was the typical equipment for fashion or advertising photography in studio. This multiplicity of incompatible but complementary systems was not irrational. They served different purposes. The digital revolution radically changed this status quo. Medium format systems became too expensive, due to the high prices of digital backs. Many photographers adopted instead versatile systems based on 35mm cameras, and many of then switched to Canon, abandoning Nikon and other brands and medium format systems (Hasselblad, Rollei, Mamiya, Pentax, Fuji...), when the full frame 35mm sensors where available. The cameras are not cheap, but compared with the medium format digital backs they are a bargain. Full frame 35mm cameras offer quality comparable to that of the film based medium format systems (645 and 6x6), allowing for a complete gamut of cameras based on the same mount, and saving a lot of money.
Several medium format manufacturers have abandoned the market, unable to compete in the digital age. Slowly, but restless, the 35mm format is gaining momentum in the very profitable market of wealthy aficionados and artists. As the prices of full frame 35mm cameras continue to go down, and the specification of these cameras continue to improve, medium format systems will be more and more challenged. The process is not yet finished.
Sometimes big guns are required for a particular assignment, or we are wealthy enough to aspire to maximum image quality without compromise (and, in passing, to the envy of anyone with smaller cameras). For this reason, many professional photographers (and aficionados, for different reasons) are continuously reevaluating the medium format offerings on the market. Until now, there are more exits than entries. Actually, only a few of the medium format manufacturers continue in business, making cameras that accept digital backs.
Hasselblad is the strongest innovator in the digital medium format market, with a new system of cameras and lenses (the H system) specifically designed for working with film and digital capture and, therefore, based on a body-and-back concept. Hasselblad is trying to reduce the gap between both devices and the actual integration of the H camera and Imacon backs is far better than any other pair of camera-and-back (including their own Hasselblad H with a back from other manufacturer, like Sinar, Capture One or Leaf). The prices are high though, far higher than a complete system based on Canon full-frame gear, for instance.
A new trend is slowly emerging: all digital integrated medium format cameras at more aggressive prices. Mamiya was the first in announcing one such device, in September of 2004, but Pentax did as well in June of 2005, with a preview of the prototypes at the PMA trade show in February of 2006. Mamiya effectively shipped the camera in March of 2006, and Pentax is expected to do the same at the Photokina trade show in September of 2006. The two machines are relatively small and more affordable than actual camera plus separated back offers, at prices not much higher than the actual Canon 1Ds Mark II. The medium format manufacturers have incorporated the price in their competitive strategies, not to exploit large economies of scale, but to preserve at least the remaining of the medium format market from the continuous erosion due to Canon competition.
The development of the Mamiya ZD was too long though. It seems that classic camera makers find problems in the development process of digital cameras. The same occurred to Leica and the Digital Module for R cameras, Kyocera and the Contax N Digital, or even Pentax and the failed and abandoned project of a full frame digital camera based on the Pentax MZ-S film camera.
Several of those projects ended with a real machine in the market, and others not. If finished, they were interesting cameras with weak points and very high prices. Only Canon succeeded with the Canon 1Ds, and then with the 1Ds Mark II and the 5D.
The Mamiya ZD has not received much attention in the press, and the veredict has been mixed. To put things clearly, it is said that the camera is good but with several flaws, and the difference in price is not be fully justified by the results. The importer’s official price of this camera in Spain, taxes included, is 11,600€ (body only). The zoom lens costs 1,782€. The Hasselblad H2D, with 22 million of pixels and a HC 80mm f/2,8 as kit lens, costs 22,000-24,000€ (depending on the reseller), and if the digital back has 39 megapixels the bill goes to the 30,000€ territory. As can be seen, the Mamiya ZD implies a sensible drop in prices in the medium format market, although it is yet much more expensive than the flagship Canon 1Ds Mark II.
The camera is very well built and smaller than expected. It strongly reminds us of the look and feel of the Contax N Digital. The same can be applied to the lens (a Mamiya 55-110mm), also very similar to the Zeiss lenses manufactured by Kyocera for the Carl Zeiss brand. It was a strange sense of deja vu.
We made several pictures comparing the Mamiya ZD with a Canon 1Ds camera. We have equipped the Canon with a big lens: the Canon 200mm f/2.8 L. Comparing the two beasts you will have a better idea of the relative size of the cameras and of the relative size of a medium format zoom with a moderate range of focal lengths.
The Mamiya ZD, in some way, looks smaller, and it is, except for the huge prism. The weight is very similar. The body of the Canon is built like a tank. The Mamiya is robust, but it doesn’t appear quite so sturdy as the Canon. The Mamiya has a better look than the Hasselblad H cameras, which makes extensive use of plastics. The only serious complaint is the small (1.8’’) LCD screen at the back. It is too small, and the menus look like those of cheap compact cameras. It falls short of any of the excellent 2.5’’ screens that we can find in any inexpensive DSRL actually in the market. The batteries of the Mamiya ZD also drain very quickly.
The Mamiya 55-100 mm f/4.5 zoom is big, and it adds a lot of weight and volume. It corresponds to 34-68mm in terms of angle of view for the 35mm format. The lens is not very fast, and the camera doesn't have a wide range of usable ISO settings either. This is not a 35mm réflex camera, although it seems to be one. Nevertheless, the depth of field depends on the format, so maximum apertures of f/2.8 or even f/4.5 offer a lot of control of that variable in 645 cameras. In order to know what are the equivalent lenses of two different formats in terms of angle of view and depth of field you must to divide the minimum f-number and the focal length of the bigger format lens by the relative crop factor. Therefore, the Mamiya 55-100 mm f/4.5 lens would allow for the same control of the depth of field than a 34-68mm f/3.2 lens in 35mm format. The ratio of the diagonals of the Mamiya sensor and a full frame 35mm sensor is 1.4X.
The zoom is very well built, smooth to handle and a pleasure to work with. It is an autofocus lens. The sensor has a size of 38x46mm and therefore the crop factor with respect to the true 645 format (42x56mm) is 1.17. It must be applied to the focal length for obtaining an equivalent focal length, in terms of the angle of view, with respect to a film based 645 camera. The crop factor also affects the circle of confusion, and therefore the depth of field changes. The traditional marks in the barrel of the fixed focal length lenses for the calculation of the depth of field aren’t valid anymore if a cropped sensor is involved. The perspective will change only if we change the distance between us and the subject of the picture. In any case, the crop factor of this camera is small, much smaller than those of some DSLRs using 35mm lenses (ranging from 1.3-1.7).
The Mamiya ZD has 21.5 million effective pixels, producing images of 4008 x 5344 pixels. The maximum theoretical resolution –Nyquist limit– is 55.7 line pairs per millimeter. With images of this size you can print a DIN A3 at 300 pixels per millimeter (6 line pairs per millimeters). The human eye can resolve, at best, 6 line pairs per millimeter at 25 centimeters distance. It is too close for an A3 print, but we tend to approach after a first look. In order to resolve 6 line pairs per millimeter of real detail in an A3 print this sensor needs to resolve 52 line pairs (8.6 enlargement factor), which is within the theoretical maximum resolution of the sensor, although it cannot be achieved. The theoretical resolution of a sensor never is reached due to diverse causes (the multiplication of the decreasing modulation transfer functions of the lens and sensor, the aliasing problems). The bigger the enlargement, the higher the resolution needed to be resolved in the sensor for a given resolution in the print. The same print from a 24x36mm sensor would need 72 line pairs per millimeter of real detail in the sensor (the enlargement factor is 12X).
We know modulation transfer functions (MTF) are decreasing, and one can get more resolution only at lower contrast levels. Medium format cameras can provide the same detail with higher contrast, or much more detail for a given contrast level, because bigger sensors need to achieve less resolution for capturing the same detail. You can compensate this, to some extent, by making more perfected lenses for smaller formats. In practice, the size of the capture device is one of the most powerful variables determining the image quality (resolution, detail, tonal range, etc.) of the final image.
The low-pass filter is a curious device. Lenses have much more resolving power than sensors. This excess of signal brings the so-called “aliasing” problems. The sensor receives information that cannot be interpreted, because is unable to reproduce all the details transferred by the lens. The sensor does not know this fact and is confused for which it believes is meaningful signal (the higher the linear resolution –the smaller the pixels– the lower the probability of excess of signal problems in the sensor). The result is a loss in resolution, as well as contrast at high frequencies and strange patterns known as monochromatic “moiré”. Due to this reason, sensor designers put a low-pass filter that cut the high frequency signal, trying to leave untouched as much of the lower frequency signal as possible. The true is that this filter affects the entire signal, and the processor must interpret the filtered signal captured by the sensor and rebuild it. Powerful processors and algorithms do this very well actually. Aliasing problems are resolved, but a loss in detail and contrast is unavoidable. The alternative solution is to take off the low-pass filter, and treat the image with software (internally or externally) only when the excess of signal leads to visible problems. In this way, under normal circumstances, more detail and contrast is preserved, and less internal processing is required. This is the solution preferred by Leica for the Digital Module for R cameras, although the Leica lenses are powerful signal transmitters (so to speak). Mamiya has opted for a middle-way solution: they provide a detachable low-pass filter. You can insert it from the bottom of the camera, or take it off. We used the camera with it off.
A different source of aliasing problems is the Bayer filter. The camera guesses the final color of each pixel by means of complex algorithms. It works very well, but sometimes we see chromatic “moiré”. What we don’t see is the loss in detail due to this filter and the subsequent estimation process. Sensors without Bayer filters, like the monochromatic one of the Kodak DCS-760M, or multilayer sensors like the Foveons, reach much higher resolutions per pixel. In this way, the efficiency of the digital image as information container improves: we get the same detail in smaller images. In our opinion, when the megapixels race ends, this will be the new way of improving the quality of the digital images (a healthy and welcomed efficiency race). The Dalsa CCD sensor inside the Mamiya ZD incorporates the Bayer mosaic, like most of the actual digital cameras. However, the quality of the color filters and the internal processing of the image are not the same between cameras, and it is to be expected to have a great color quality from an expensive camera like this one. In fact, this happens to be true, and the images, free of the low-pass filter’s influence, have great detail per pixel and rich colors.
Many people ask, “why I need so many pixels?” Now consider an argument in favor of the megapixels race. We know the human eye can resolve, at best, 6 line pairs per millimeter from a destance of 25 centimeters. If we make a 8x12 print (DIN A4) at 6 lp/mm (300 pixels per inch, ppp) the image needed will have 8 million pixels. If the print is double that size (A3) the viewing distance must to be longer, and the resolving capacity of the eye will fall, so 240ppp (5 lp/mm) is more than enough, needing 10 million pixels. Many editorial assignments ask for a double page at 300ppp, and a A3 print with that resolution requires 16 millions of pixels. Even bigger images could be convenient for cropping of for big enlargements. Now comes the key argument in favor of bigger images. The real resolution (detail really resolved) is lower than the theoretical resolution of the sensor, which determines the size of the digital image (in number of pixels), and therefore, an image of 8 millions of pixels cannot contain enough real detail for a A4 print reproducing a pattern of 6 lp/mm. A bigger than needed image will have a particular percentage of real detail that can be preserved after downsampling. If you need 16 millions of pixels for a print, a bigger number will be welcome for more (after downsampling) real detail. This is one of the advantages of medium format’s massive number of pixels.
Another important parameter in image quality is the dynamic range and the signal-to-noise ratio. They depend on the size of the pixels... and many other factors. In spite of the very high pixel count, the pixels in the Mamiya ZD are big. Canon considers 6.4 microns as the optimal size (the length of one side of the square), given the current state of their technology. Most manufacturers of DSRL cameras tend to situate their sensors just below 7 microns of pixel pitch, or even below 6 microns. The Olympus cameras and the Nikon D2X have pixels around 5.5 microns. In many technical documents 5 microns is assumed to be the minimum assumable size, if we want to keep other properties safe and well. The sensor of the Mamiya ZD has pixels of 9 microns, so they are really big, in relative terms. The new 39 Megapixels digital backs (from Capture One and Hasselblad, based on a Kodak CCD sensor) have pixels of 6.8 microns, very similar to many DSRL cameras. The bigger the pixel size, the lower the photon noise, which is a limiting factor for the signal-to-noise ratio. A higher signal-to-noise ratio means more dynamic range and less noise, although there are more factors involved.
Dynamic range is like the length of a staircase, and the bit depth is like the number of steps. The Mamiya ZD has a 14-bit per channel A/D converter, which generates an image of 12 bits per channel. Many digital backs, including the Digital Module R of Leica, employ 16-bits per channel converters, which improves the tonal gradation. In spite of this, the Mamiya provides images of superb quality and smooth and subtle variations in color and tonality.
The following pictures are from a studio scene. The Mamiya used the 55-100mm zoom at the longer focal, which gave us the angle of view of a 72 mm (=100/1.4) lens in full frame 35mm format. The exposure time was 1/100s, and the aperture was set to f/22 (equivalent to f/16 in terms of depth of field for the 35mm format). The size of the Mamiya image is 35MB (5336 x 4008). The camera was mounted on a tripod. The images are JPG files from the RAW files read with the default parameters in Adobe Camera RAW 3.3.
We show here two 100% crops (sizing 420x640 píxels). The first cropped image is of the original RAW file saved as JPG for the web, without modifications. The second image comes from the RAW file after applying a levels adjustment and a sharpener algorithm with Photoshop. We did it on the luminance channel using the unsharp mask command. The parameters were 150 (amount), 1.5 (radius) and 2 (threshold). The image of the Mamiya is very big, but it has not low-pass filter, so we were conservative.
Crop. Mamiya without sharpening
Crop. Mamiya with sharpening and levels adjustment
We didn’t notice any moiré problems in the fabrics, which is remarkable considering the absence of low-pass filter.
The following sample shows a collection of precious Nikons, from the good old days. Parameters: 100mm, 1/80s, f/11. The pictures were adjusted in Photoshop (sharpening and levels).
Mamiya. Complete picture. Sharpening and levels adjustment
Mamiya. Crop. Sharpening and levels adjustment
The Mamiya ZD camera has a range of ISO settings ranging from 50 to 400, with intermediate 1/3 steps. We tested the performance of the camera at 400 ISO under normal conditions ( not in a cave without flash ) at 1/25s f/5. The noise can be seen in the shadows, and some detail has evaporated, but it is acceptable. The computer screen is one thing and the print is a different one. For instance, downsampled images will mask a good amount of this noise. We did not apply any noise suppression by means of specialized software like Noise Ninja or Neat Image, which can be done for better-looking result. The lost detail though can not be recovered.
The dynamic range is not easy to measure. In the next sample we can see how a very contrasty scene has no burnt highlights or blackened shadows (except a few minor zones). The crop shows details in the shadows and the highlights, with a lot of room for additional improvements in Photoshop, if needed. The image comes directly from the RAW, without manipulations. Parameters: 1/160s, f/11, ISO 200:
Eduard de Kam complained about the quality of the JPGs obtained directly from the camera. It depends of the internal processing. We will not pay attention to JPG files though. We assume that the natural buyer of this beast will have enough money for several memory cards and a hard disk. The best of a camera can be obtained in the computer, from RAW files, using powerful applications for the reading of the RAWs and their manipulation. Mamiya offers a simple but interesting program for this task, and we will review it as well.
The application is called Mamiya Digital PhotoStudio (DPS), and the current version is the 1.2.0. It is a small, simple but elegant program. It reads the RAWs generated by the Mamiya ZD and allows for a set of adjustments, several of them are the basic ones but others are not. It has a basic palette and a Folder Tree for easy navigation. Additional features are included in add-hoc windows that need to be called via menus. We have the well-known curves/levels sliders, color balance, warning levels for highlights and shadows, white balance, noise suppression (although you cannot differentiate luminance and chromatic noise), processing options (file format, color space), sharpening (very basic), image control (sharpness, saturation, contrast, exposure compensation) and lens correction (vignetting, distortion and chromatic aberration).
The controls are very simple, redundant at times and your screen will be flooded with many small windows very easily. You will be opening and closing windows all the time. The software is enough for basic manipulation, but Adobe Camera Raw supports this camera and it offers more control and an integrated interface. Adobe Lightroom, which is built upon Camera Raw, also supports the camera, offering a lot of additional possibilities for adjustment.
If you have an expensive camera like the Mamiya ZD you will want to extract as much from it as possible, and RAW shooting and later development with a capable application are fully recommended. The Mamiya DPS software is nice but it is too basic. The only interesting feature is the lens correction module, but we were unable to know if it uses some kind of mapping of the characteristics of the lenses or not (Hasselblad and Leica do this). The Mamiya DPS allows you to control the camera from the computer, in tethered mode.
We think medium format cameras offer better image quality, but at a price. These cameras are more difficult to handle. Each professional or aficionado should evaluate his needs. The market seems to think that alternative systems based on the 35mm format are more convenient: wider arrays of diverse, faster and stabilized lenses, good performance at high ISOs, not so much lower resolution and more versatility (one mount for many different tools). Mamiya has successfully resolved several drawbacks of medium format digital: relative price (to some extent) and size. The ZD seems to be useable for handheld fast operation, due to its form and size, but this is not exactly true. The unique selling point of medium format cameras is superb image quality at low ISOs, in the studio or in location, with tripod mounted cameras. Mamiya has carefully preserved these typical advantages of the medium format cameras. Whether this will be enough for Mamiya and the medium format market in the long run, we cannot know it. Time will tell.
We, the authors of this article, have written different pieces about photographic equipment, in Spanish, published elsewhere. Efraín García (Efra) is a professional fashion and advertising photographer, and Rubén Osuna is University Professor at the UNED, Madrid. Professional photographers working in Madrid know very well Fotocasión, a big shop of photographic equipment and assistance to professionals. They kindly loaned us the Mamiya ZD for these tests.