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Imacon Ixpress

A Unique Medium Format Digital Solution

This review is part of a larger series of ongoing articles and reviews of medium format digital backs.
If you have not already done so you might wish to begin by reading my Digital Back Survey
and then refer to the other reviews in this series that are linked at the bottom of that page.

I have always had high regard for the Danish company Imacon. I have owned one of their Flextight Photo scanners for several years, and have found that it is capable of desktop scans fully the equal of those from drum scanners. It has a unique film holder that maximizes film flatness, (especially important with roll film and sheet film) and the entire range of scanners utilize the finest components. I have found this scanner to be utterly reliable. It was in daily use for nearly three years before I switched most of my work to shooting digitally late last year (2002).

Which brings us to their medium format digital backs. Until 2003 Imacon's line of digital backs didn't interest me, since these were primarily studio tools and my work is done almost exclusively in the field. But in early 2003 Imacon began shipping the Ixpress 96 back, a 16 Megapixel single shot medium format back designed for location shooting. I couldn't wait to try it out.

An opportunity was made available in the summer of 2003 by the good folks at Headshots in Toronto, one of Canada's leading equipment retailers and professional rental houses. They had just been appointed the Imacon distributor for Canada and the first Ixpress units had recently arrived.

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The ImageBank

The Ixpress is a two piece unit. The back is quite small and attaches to a separate unit called the Imagebank with a thin flexible cable. The transfer medium is apparently Gigabit Ethernet, so it's very fast. The Imagebank has a belt clip, or can be easily put in a coat pocket. The cable connectors are quite elegant, with solid but easy to attach and detach connectors.

What is the ImageBank, you may ask? It is a combined power supply for the back as well as a 40 GB hard disk, along with additional support electronics that help to reduce the size and weight of the camera back itself (which is consequently very small). Let's deal with the hard drive first. At 40GB, it's large enough to store 1,000 96 MB losslessly compressed files, something that would take dozens of 1 GB memory cards.

Now, you may say, I don't need pockets full of 1 GB cards; I just need a few and then can copy them to a PC or digital wallet device. Sure, but have you ever done this on location shoots? It's time and battery consuming, and tedious. Also, it means you need to have a laptop computer with you on location. With the ImageBank, nothing more is needed to shoot up to 1,000 frames, which even for a busy pro is several days shooting.

When you get back to the office, motel, tent, or wherever, you then attach the ImageBank to a Firewire connector on your computer and start up the Flexcolor software. It automatically senses the ImageBank and displays thumbnails of the contents of the drive. You can now copy selected or all files to your computer, deleting or leaving them on the ImageBank as you wish.

The Imagebank and the connected camera back is powered by a single Sony L series Lithium Ion battery. Imacon claims up to 8 hours on a single battery, and in my time with the unit I found myself getting 4-5 hours. Excellent performance, and two batteries is therefore likely enough to get you through a busy shooting day.

Oh yes, in tethered mode, for shooting in the studio, files pass directly through the ImageBank from the back straight to the computer.

All of this begs the question — how annoying is the fact that there's a cable between the camera and the back? After a week or working with the system my best response is that it's a nuisance when compared to working with an integrated back like the Kodak DCS Pro Back 645, but probably manageable for most photographers. One needs to constantly remain aware of the cable so that you don't walk away from the tripod while the ImageBank is still hanging on your belt. Something's going to give — with possibly expensive consequences. If I were going to be using the Ixpress back on a tripod I would arrange some sort of mount to attach the Imagebank to a tripod leg so as to avoid this problem.

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A True 16 Bits

The Ixpress 96 is a true 16 bit back. What does this mean, and is this, as Martha would say — a good thing? If you're not familiar with the concepts, read my tutorials on Understanding Bit Depth and also Expose Right. Briefly, all current digital SLRs are 12 bit devices. That means that they are able to record (2^12) or 4,096 different shades of gray per color channel. A true 16 bit device (2^16), like the Ixpress back, is capable of 65,536 shades of gray per channel, or billions of shades or colours if you count all three colour channels combined.

The reason that this is worthwhile is because, as described in the tutorial Expose Right, because digital imaging chips are linear, each stop (doubling or halving) of exposure contains not one fifth (assuming for this example a 5 stop dynamic range) but rather the following in the case of a 12 bit chip.

Within the first F/Stop, which contains the Brightest Tones
2,048 levels available
Within the second F/Stop, which contains Bright Tones
1,024 levels available
Within the third F/Stop, which contains the Mid-Tones
512 levels available
Within the fourth F/Stop, which contains Dark Tones
256 levels available
Within the fifth F/Stop, which contains the Darkest Tones
128 levels available

In the case of a 16 bit chip, like that in the Ixpress, the table would look like this...

Within the first F/Stop, which contains the Brightest Tones
32,768 levels available
Within the second F/Stop, which contains Bright Tones
16,384 levels available
Within the third F/Stop, which contains the Mid-Tones
8,192 levels available
Within the fourth F/Stop, which contains Dark Tones
4,096 levels available
Within the fifth F/Stop, which contains the Darkest Tones
2.048 levels available

In other words, a 16 bit back has more data in its darkest range than a 12 bit back does in its brightest range. This theoretically translates into greater colour depth and a greater ability to work with the image in the RAW converter and in Photoshop in 16 bit mode. (Photoshop 8, due later this year, will allow many more manipulations in 16 bit mode than does earlier versions).

Now you can appreciate what a significant difference a true 16 bit mode digital back can mean. But, how does this translate in the real world? One of the ways I tried to test this is by creating a worst case scenario — very high contrast with deep shadows and using high ISO, so that the camera would be at its worst in terms of noise. I also let the cameras sit in the sun for 20 minutes on a warm day before conducting the test.

Below you see the results of a comparison with the Canon 1Ds, which is a remarkable camera is terms of low noise images under almost any circumstance, as well as against almost any competition. These shots were taken at ISO 400, the Ixpress' maximum speed, and with a uniform manually-set aperture of 1/500 sec at f/8. An incident meter reading was used.


Imacon Ixpress 96. ISO 400
Canon 1Ds ISO 400 — detail
Imacon Ixpress 96 ISO 400 — detail

What you see above is a testament both to the incredible low noise of the CMOS chip in the Canon 1Ds and the amazingly wide dynamic range of the Imacon Ixpress. Three things can be clearly seen.

1 — though I wasn't testing for it, the Canon 1Ds has less shadow noise at ISO 400 than does the Imacon.

2 — the colour rendition of the Imacon is more accurate under these conditions. The flowers are indeed a pastel violet, not the bright blue that the Canon has made them.

3 — the Canon has blown out the highlights, while the highlights with the Imacon are full of detail. There's slightly more detail in the shadow area with the Imacon, but only slightly.

Based on this test, and quite a few others, I would judge the Ixpress as having a usable dynamic range of about one half additional stop over the 1Ds.

This of course begs the question — is the Imacon's 16 bit mode that much superior to a camera or back working in 12 bit mode? Based on this and other tests, including against the Kodak DCS Pro Back 645, which uses essentially the same Kodak manufactured imaging chip as does the Ixpress, the answer has to be a qualified yes. I say qualified because while the difference is certainly there and visible, as shown above it is nowhere near as huge as I would have expected or would have liked it to be for that matter. All other things being equal, it's definitely worthwhile, but then, are all other things equal?

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Reduced Frame 645

It needs to be understood that the Imacon Ixpress back, like other 16 Megapixel medium format backs, does not cover the full 645 frame. It covers an area of 37 X 37 mm. This has certain implications. One of them is that the so-called "sweet spot" of the lenses is used and issues like chromatic aberration, as seen with some full-frame 35mm DSLRs, are largely avoided. It also means that the 645 format now becomes "square", allowing for both vertical as well as horizontal cropping of the format frame, after the fact. In other words, all of the pros and cons that we've had with 6 X 6 cm square medium format for nearly a century now apply to 645 format 16 MP digital.

There's also another aspect to consider. Though 645 format has a 1.5X size advantage over 35mm, and therefore lenses need to be thought of as covering a smaller angle of view because the frame is reduced with the current generation of 16 Megapixel backs by the same amount, 645 format lenses end up giving the same angle of coverage as do 35mm lenses. So, a 50mm lens, is a 50mm lens. But, this also means that wide angle coverage is wanting, and so since a 35mm lens is the widest generally available for 645 cameras, that's the widest that one can shoot without stitching frames in software.

When I started using the Imacon and also the Kodak Pro Back I thought that I would find working with less than "full-frame" 645 to be problematic. Reduced frame in 35mm digital terms usually means a smaller and dimmer viewfinder. Not here. The reduced coverage area is defined by lines on the interchangeable focusing screen. No viewfinder brightness is lost, and in fact I found that being able to see outside the frame to be a real plus. Just as with an M Leica one can judge the framing much more accurately because one is aware of what lies beyond as well as what's within. (The Sigma SD9 uses a technique of putting a dim mask around the part of the screen that isn't recorded, a worthwhile design for the same reason).

I should point out that while the Kodak DCS Pro back ships with full replacement focusing screens for the supported Mamiya, Contax and Hasselblad models, the Imacon Ixpress is provided with a thin plastic insert that sits on top of the existing focusing screen. Both solutions show the new framing lines, both horizontally and vertical, but for $16,000 one would think that Imacon could provide a proper replacement screen rather than just an inexpensive insert.

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The LCD Screen

Possibly the most controversial aspect of the Imacon Ixpress is its monochrome LCD screen. This displays only a histogram, not a review image. The advantage of being in B&W only is that it has much lower power consumption than would a colour screen. In fact the LCD is always on when the back is powered, and doesn't even have an on/off switch. I suppose that there is also some saving in not having to processes the image for screen display, but I can't imagine that it's significant.

Is the lack of a colour review image a drawback of the Ixpress back? I've been giving it a lot of thought. If we didn't have the example of 35mm DSLR's, all of which have such displays, and the competitive Kodak DCS Pro Back, which also has one, I suppose that it wouldn't seem like such a loss. But if, as I have, one has been working with systems that offer this capability then the lack is glaring. Users of other digital backs that lack any form of LCD display at all are working tethered to a laptop, and therefore have a large screen for image review, so a comparison with these isn't quite fair.

In the end I find this to be a failing of the Ixpress back. While small colour LCD screens can't tell you much about an image that the histogram doesn't convey, it is reassuring to be able to see if, for example, the subject of a portrait had her eyes closed, or if the leaves were blowing in the wind or managed to remain still in a particular frame, or if the cropping is exactly right or not. All of these can't be appreciated from a histogram alone.

Of course it could be argued that when shooting film one doesn't have any of these reassurances. But then, why obviate one of the main advantages of working digitally?

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Beep Beep

What I did come to appreciate is the acoustic feedback provided by the Imagebank. As soon as a shot is taken there a descending tone for underexposure, a rising tone for over-exposure and a chirp for perfect exposure. One quickly becomes familiar with this audio assistance and wonders why no one ever thought of it before. Very nicely done!

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Fittings & Syncing

The Ixpress back can be fitted to a wide range of medium format cameras, including the Hasselblad 500 series, the new Hasselblad H1, Fuji 680, Rollei 6008i and AF, Mamiya 645 AF and AFD as well as the larger RZ, and the Contax 645 and Horseman Digiflex. For cameras that don't have a fully electronic interface, like the older Hasselblad 500 series, you need to add a sync cable between the back and the lens' PC flash contact. This tells the back that the camera has been fired, and triggers the back's exposure while the camera's shutter is open. A variety of different sync cables of different sizes and sorts is provided with each back.

To fit the Ixpress to any one of the supported cameras requires an extra cost adaptor, and these can be fitted by the end user. So if you work with more than one brand or type of medium format system the same Ixpress back can be fitted to several different cameras, but it does require some tools and a bit of time to accomplish this. The Kodak DCS 645 Pro Back, on the other hand, is made for a specific camera model and can't be used on any other.

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The Computer and Software Interface

The software supplied with the Ixpress back is Imacon's justly well-regarded Flexcolor. This is the exact same software as is used with their line of professional scanners. I've been using earlier versions of Flexcolor for years, and in terms of its ability to extract the best from an image file, and to do so with an intuitive user interface, there are few programs that can match it.

So, you've been out shooting with your Ixpress back for the past 2 days and you have a few hundred images on the Imagebank. You get back to the office and plug a standard Firewire cable into the Imagebank and then into your PC or Mac. When you launch the Flexcolor software the Imagebank is recognized and thumbnails of all the files on the Imagebank are transferred quickly to the PC. These moderate-sized TIFF files (about 1.3 MB each) are generated automatically by Flexcolor, and the files are stored in a directory called Scratchpad in the root of your primary hard disk. You are also given the option of transferring the RAW files themselves to the hard disk (and optionally deleting them from the Imagebank) or of leaving them there and downloading them one at a time as needed.

The system is well thought out and works quite efficiently, especially when you consider that each of these RAW files ends up uncompressed as 140 Megabyte 16 bit TIFF files.

My concern lies in the fact that though the Imagebank hard disk connects to the PC via Firewire, only the Flexcolor software can see it. In other words, you can't transfer the files, or for that matter even see the Imagebank directory and files without Flexcolor. This could prove to be problematic when working away from ones own computer system, or in the event of a computer crash or other mishap. Being totally reliant on a proprietary transfer protocol is therefore a bit of a concern.

I was also concerned that I experienced several glitches, though none of them were serious. Occasionally the Imagebank would "lock up" when first attached to the PC. This usually required nothing more than unplugging the Firewire connection and then reattaching it again, though on several occasions I needed to remove the battery on the Imagebank, effectively cold-booting it. It would always then connect properly with no extra fuss.

There were also some frustrations in installing the Imagebank for the first time. A driver file was needed, and Windows XP's "Wizard" said that it couldn't find the required file even though I explored the supplied CD-ROM and searched the Imacon web site for the file. A call to Imacon's very friendly and efficient customer support desk eventually lead to the fact that the file had been installed in the Flexcolor directory on my hard disk, and all I needed to do was point the Wizard to it. In all I wasted a couple of hours over this, and was frustrated by the fact that drivers should either be automatically installed in the proper location or be left on the CD-ROM where they can be easily found by the driver installation Wizard. In this case neither was done. Incidentally, I installed the system on my Mac under OS X and had no problems at all.

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3F

The Ixpress stores files in a TIFF format called 3F, with the extension FFF. The appeal of this format, which Imacon is promoting and hopes that other companies will adopt, is that the header file contains a complete history of any changes made to the file within the RAW processing software. This can simplify later alterations, and is somewhat similar to the Photoshop History palette concept, except that in this case the history transactions remain with the file.

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Impressions and Conclusions

A number of different factors come into play when evaluating any given piece of equipment. Personal needs and biases are one aspect and ones expectations are another. In the case of my recent review of the Kodak DCS Pro Back I was initially predisposed not to like it, for reasons that are detailed at the beginning of that review. After a week of field use though I was so impressed that I ended up buying one for my own use. In the case of the Imacon Ixpress, because of my years of excellent service from my Imacon scanner I was predisposed to like it, yet in the end was left with a strangely neutral impression.


Muskoka Wooden Church. July, 2003
Hasselblad 503CW with 150mm Sonnar & Imacon Ixpress @ ISO 100

This may in large measure be due to the fact that the Ixpress is a cabled two-piece unit, and my personal style of working is geared more toward the advantages of an integrated single piece solution, such as the Kodak. It needs to be stressed that another photographer with a different working style might come to the opposite conclusion.

The other strike against the Ixpress was the lack of an image review capability. While I knew going-in that this feature wasn't there, and believed that it wouldn't necessarily be an impediment to my workflow. In fact it was. I simply didn't have the confidence that the shots that I was getting were what I wanted, because I had become so used to this capability from using other digital cameras and backs. If I was coming straight from being strictly a film user I might not have missed it, but miss it I did.

Finally, I had high expectations of the fact that the Ixpress was a 16 bit device. In the end my tests and comparisons showed that while the difference between it and 12 bit cameras and backs were visible on targeted tests, in general real-world shooting situations I could see little appreciable advantage.

The bottom line is that for some photographers the tethered nature of the Ixpress may be mitigated by the storage capabilities of the Imagebank. And, some photographers may find that the true 16 bit capability gives them an edge in some situations. And certainly one of the strengths of Imacon's offering is its excellent Flexcolor software.

If you think that the Ixpress may meet your needs I urge you to contact your dealer or distributor and have a demo. It's a beautifully designed and built product capable of producing excellent image quality. If a 16 Megapixel medium format back is on your radar screen then the Imacon Ixpress is definitely worth a demo.

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Update: October, 2003

Imacon has announced that the Ixpress is now available with both a colour LCD review screen and a 22MP imaging chip. The screen corrects one of the major concerns I had regarding field use of this back and the larger chip brings the back to state-of-the-art size. An upgrade for existing owners is offered. You can read more about it here.

 


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Concepts: Hasselblad, Camera, Liquid crystal display, Digital single-lens reflex camera, Eastman Kodak, Digital photography, Tagged Image File Format, Kodak DCS

Entities: Toronto, ImageBank, Kodak, Canon, Sony, Mamiya, Contax, Hasselblad, Mac, Canada, ISO, LCD screen, Hasselblad 500, Windows XP, OS X, Imacon Ixpress, sec, Michael Reichmann, Imacon, Martha, Flexcolor, SLRs, Hasselblad H1

Tags: Ixpress, 16 bit, cameras, medium format, Kodak DCS, Imacon Ixpress, true 16 bit, 12 bit, digital, bit mode, digital backs, hard disk, chip, image, Flexcolor software, review, bit device, Canon 1Ds, format digital backs, Megapixel medium format, cable, dynamic range, Hasselblad 500 series, bit chip, 35mm, computer, Brightest Tones, Digital Back Survey, earlier versions, Megabyte 16 bit, dcs 645 pro, imaging chip, low noise, colour lcd, lcd screens, danish company imacon, mamiya 645 af, medium format backs, format 16 mp, sync cables