Chillout TGIF: Phase One XF IQ4 150 with lenses

I had a chance to try out the Phase One XF IQ4 150 system with lenses and the Broncolor Siros L strobe recently and took it on a trip to Switzerland where I used it to photograph watches, ateliers and scenery. Here is my impressions on the system. Is it the best camera system money can buy?

We cut straight to the chase. This is definitely the camera system which yielded the best image quality I have ever used. It is also the heaviest, and the most expensive camera I have ever used.

Phase One XF system

The Phase One system is a modular system. This contrasts to the earlier medium format digital cameras we have reviewed like the Hasselblad X1D, the Leica S Type 007 and the Fujifilm GFX 50R. In those systems, the body comprise of a non-detachable back and a non-detachable finder system. In the modular system, the body comprise of the mirror box and focal plane shutter mechanism with electronics. A finder system with the option of several interchangeable systems like the prism finder or a waist level finder is attached to it. The digital sensor and rear LCD is in the digital back, which can also be detached and exchanged for another. As an example, the Hasselblad H system is a similar modular system.

The base is the XF System body and comes with a prism finder which is attached to the top of the body. This can be removed, and replaced with a waist level finder. The camera I had came with the top of the line back – the IQ4 150. Hence the notation Phase One XF IQ4 150.

This is the fourth generation IQ back from Phase One, and the sensor is a 150 Mpx Back Side Illuminated (BSI) sensor. The XF body can also be paired to older backs from IQ1 to IQ3, and also to the current generation of IQ4s – the Trichromatic 100Mp and the 150 Mp Achromatic (black and white only) backs. All components can be freely interchanged with full functionality across.

The lenses which go along with the IQ4 150’s ultra high resolution back are the Schneider Kreuznach Blue Ring series. Phase One also have another series of non-Blue Ring lenses, branded Phase One but also made by Schneider Kreuznach, which can be used with the lower resolution backs, but not recommended for the 150Mp back. Schneider Kreuznach is a manufacturer of industrial and photographic optics founded in 1913 by Joseph Schneider, based in Bad Kreuznach, Germany.

The Blue Ring lenses all feature leaf shutters for flash synchronization at all speeds up to 1/1600s. The XF body provides a focal plane shutter which goes to 1/4000th of a second with a flash sync of 1/125s.

The sensor

The IQ4 150 back features an industry leading sensor in the form of the 53.4 x 40.1mm CMOS BSI sensor. This is the largest sensor in the photography market, the same size as that found in the IQ4 100 as well as the Hasselblad H6D-100 and a full 2.5x larger than that of full frame DSLR cameras, and 1.5x larger than cropped sensor mirrorless medium format (44×33 sensors found in Fujifilm GFX and Hasselblad X1D).

However the IQ4 150 features the Back Side Illuminated sensor, which is a more efficient pixel design than the standard Front Side Illuminated sensor. Each pixel captures more and better quality light which translates to a more accurate render with improved color, detail and noise handling within the RAW file.

A full treatment of the BSI is beyond the technical reach of this article, but a quick introduction is found at this video linked here (20 minute video):

Currently, only two other cameras offer the BSI sensor – the Fujifilm GFX100, and the Sony A7mkIV. All the sensors are manufactured by Sony, and it is speculated that each is cut from the same large wafer. At the full frame dimension of 36×24 it yields a 64Mpx resolution, used in the A7mkIV. At 44×33, yields 100Mp as used in the GFX100, and at 54×40, the same wafer yields 150 Mp and is used in the IQ4. The sensors are customized for each manufacturer, and Phase One works directly with Sony for the development of their 150Mp BSI sensor.

An electronic shutter is also implemented in the IQ4 back, allowing 1/4000s exposure. But the usual issues with rolling shutter and very slow sync speeds (0.3s) plague the electronic shutter, so I usually avoid it.

Ergonomics

The body is ergonomically designed, fitting the larger hands better than smaller, but is comfortable in my hands. The camera system is rather large and bulky, and one is hard pressed to use it in stealth mode. Though comfortable to hold, it becomes tiring after a while as the camera is very heavy. The XF IQ4 150 (1890g) with either the 45 (1220g) or 120 (960g) weighs in at about 3 kg. This is one seriously heavy beast.

The controls are fairly logically laid out, and buttons around the body and back are all fully customizable. The body features a OLED touch screen at the top of the camera, and the back carries a large LCD touch screen.

For someone like me, who has been using the Hasselblad H system for the last decade, it takes a bit of getting used to the buttons, but after a short familiarization, muscle memory takes over and I can operate the camera easily.

The camera requires two batteries to operate- one in the XF body, and another in the IQ4 back. Both batteries are the same type, and I found that the IQ4 battery to run out of power faster than the one in the back, typically I can use two in the back for every fresh one for the body. If the back is in live view mode, the battery runs out even faster, and the back can get rather hot, reaching temperatures of up to 60C at the surface. This is within specifications, as the entire massive back is used as a heatsink for the sensor. Thermometers within the back monitors the temperature of the sensor, which can reach 100C in normal operations. Needless to say, the battery life under these conditions become very short. Multiple batteries is a needed, and the Phase One XF system is delivered with 4 batteries.

Useful features

The XF IQ4 150 features two very useful features:

• Focus stacking
• Frame averaging

Focus Stacking Tool

I discussed Focus Stacking in my review of the Fujifilm GFX 50R. In the Fujifilm system, the photographer has to manually set the near focal point, then three parameters in the Focus Bracketing Tool – the number of frames, the step size and the interval.

In the Phase One system, this is further automated. The photographer first sets the near focal point by focussing the lens at that point, and camera stores the position with a button push. The lens is then focussed at the far focus point and the camera memorizes that position with another button push. Phase One then calculates the number of frames required and the step sizes and automatically displays this. This calculation is very sophisticated, and uses the information of the lens and back attached, the aperture set and the circle of confusion needed for critical focus. The photographer can over-ride any of these settings manually if he so wishes. This is a good thing, as I find the camera calculations are based on very large prints, and thus errs on the cautious side for other applications. It specifies far too many frames than needed as estimated by experience. As an example, it frequently specifies that 100 frames is required when I know that 20 will work with small prints (up to A2) or web images. This is easily done by reducing the number frames with the dial at the back of the body.

This tool makes focus stacking repeatable and is a workflow time saver in a high volume production environment.

Frame Averaging Tool

A very special tool is also available in the XF IQ4 150. This is the Frame Averaging tool. I used this in the photographs for the Bvlgari Christmas Lightup article. I used the Phase One XF IQ 150 digital camera with the Schneider Kreuznach 45mm f/4 Blue Line lens on a very sturdy Gitzo tripod and a Photoclam Multiflex geared head.

The advanced and special technique of frame averaging was used to produce the images similar to long exposures but without the use of ND filters. The long exposure allows the scene to be photographed with what seems like a scene sans people, while the reality is that I photographed the installation after it was open already to public, and there were many people milling around. This technique is also used to create images of moving water or clouds in good light, which does not look like its frozen, but a misty looking effect suggesting the flow.

The standard technique for these images is to use an Neutral Density (ND) filter, and long exposures. ND filters are pieces of dark glass placed in front of the lens, and cuts down the amount of light. But they are heavy, fragile and add a colour cast.

The XF does this with the Frame Averaging Tool which takes up to 1000 frames internally, and automatically averages them to produce a very sharp, clear image. We used 50 to 100 frames for the exposures above.

While this technique is known and can be used with any camera, it becomes practically cumbersome when the photograph calls for 100 shots to be manipulated in Photoshop’s averaging tool. The Phase One camera does this automatically, and produces a single file in real time.

The Schneider Kreuznach lenses

The lens lineup is very strong and complete, as one might expect from a system intended for professional use. The ecosystem of Schneider Kreuznach Blue Ring lenses are all equipped with leaf shutters, and comprise of 11 prime lenses ranging from 28/4.5, 35/3.5, 45/3.5, 55/2.8, 80/2.8, 110/2.8, 120/4 Macro, 120/5.6 Tilt/Shift (no leaf shutter, so focal plane shutter operation only), 150/3.5, 150/2.8, 250/4.5. And two zooms 40-80/4.0-5.6 and 75-150/4.0-5.6 with a 2.0 TC.

Specific for my needs to photograph watches, the 120/4 Macro is a true macro, throwing a full 1:1 image on the sensor without the use of extension tubes. Three extension tubes are available – 11.8mm, 23.6mm, 35.4mm. These are stackable for higher magnifications. In operation with these tubes, all lenses are limited to manual focus and focal plane shutter use but retains electronic contact to ensures auto aperture functionality. I did not test the extension tubes.

I had the 45/3.5 and the 120/4 Macro for my use, and found both to be exemplary optically. Colour, saturation, contrasts and rendering of images are outstanding in both these lenses. The sharpness and resolving power of both are also the best I have encountered.

The autofocus motor feels quite rough and has a grainy feel, and is rather loud in operation – grinding as it finds the focus. The autofocus is quite slow, and hunts quite a bit in dark scenes, but when locked, it is very accurate and produces superb results. The lenses can operate with autofocus or manual focus. In autofocus mode, the focus ring is locked. It is released by pulling it back to engage manual focus. The feel of the ring is smooth and precise. In contrast, the Hasselblad H system features full time automatic manual and autofocus ability – in autofocus mode, just rotating the focussing ring will cause the lens to focus manually.

The strobe: Broncolor Siros L

I had with me for the week the Broncolor Siros L strobe system. This is a monoblock design like my vintage Profoto Compact 600, but is battery operated. A white LED modeling lamp is included, and at full power, the flash output is 400Ws. This is quite powerful, and way more than the maximum output of speedlights.

The Broncolor Siros L is excellent – with good flash to flash consistency in power and colour temperature. The unit operated flawlessly, and is equipped with advanced control features where the strobe can be controlled via a Smartphone app through its WiFi capability, or wirelessly via its own control unit. I did not test these advanced features, as I used my normal Godox trigger to release my rim light which is a Canon EX580II speedlight. The Broncolor is set to optical slave mode, and is triggered when it sees the Canon go off. This system worked flawlessly.

The image quality

Resolution. Contrast tone and colour fidelity

With 150 million pixels on a sensor this large, there is plenty of resolution. But a medium format digital image is more than just resolution. The larger photosites and 16 bit architecture of the files mean that more information is captured. Take this example of the portrait of Patrick Pruniaux, CEO of Girard-Perregaux and Ulysse Nardin. The portrait is the same one as was used in the GP Absolute Rock review. The full sized image is 14,204 x 10,652 pixels, which will print to 120.26 x 90.19 cm without upscaling at 300dpi. At this image size, a print of this image can be scrutinized as close as one wishes.

The colour rendition is absolutely spot on. The tonal changes with the light fall off from Patrick’s right side to his left is smooth, and shows a very natural fall off. Even the focus fall off from the absolute sharpness on his eyes to the ears is smooth and gradual, with a beautiful bokeh showing of the background.

See the 100% crop of the image, shown below. Focus is nailed perfectly. Each strand of his eyebrow and eyelash can be distinctly seen in sharp focus. His iris scan be completely read. The small blood vessels on the whites of his eyes is clear and sharp, as are the flakes of skin on his eye socket.

This is just one example. The images in the Petermann-Bedat and Rexhep Rexhepi Atelier visits were also shot with the Phase One system, and can be further scrutinize as proof of this ultimate image quality.

Low light performance and dynamic range

High ISO performance is also excellent. The camera goes from 50-25,600. I found little difference in noise and colour fidelity up to about 3200. At 6400, the noise starts to intrude in the darker areas, and continues up to 12800 where it is quite visible on large prints. But what is interesting is that the noise shows itself has a film like grain structure rather than multicolour pixelation. And the resolution and colour fidelity is still very good at 12800. The dynamic range of the back is publicized as a full 15 stop. While there is no way I can verify that, I find this figure to be believable as I routinely pull 3 to 5 stops from the shadows to show a nicely exposed image with good resolution and colour detail.

More photographs and examples in next week’s follow-up article.

Concluding thoughts

If one’s quest is the ultimate image quality, the Phase One XF IQ4 150 with the Schneider Kreuznach Blue Ring system certainly fits the bill. The image quality is truly the best I have ever seen, and by quite a margin. The workflow capabilities of the system is also outstanding and superlatively impressive. Focus stacking is consistent, repeatable and fast. Frame averaging is currently a feature no other digital camera offers, and saves the weight of carrying additional stack of ND filters and workflow efficiencies of not having to deal with colour shifts and other filter issues. This is an outstanding feature.

The build quality is literally like a tank. Phase One often demonstrates the strength of the camera and back by removing the back, and having a person stand on it. Something that is done routinely. The entire body, back and even the lenses are extremely sturdy and well built.

This means that the camera will withstand the rigours of multiple professional shoots. But the flip side is that the system has considerable bulk, though as seen in the photograph above, it not really larger than the comparable medium format professional Hasselblad H system. The system is also extremely heavy (heavier than the H), and the use of a sturdy tripod is mandated. Though I will show some walkabout photographs next week, when I shot with the XF IQ4 with SK lens hand-held.

The final hurdle is the price. At a system price of about S$ 83,000 with two lenses as tested, this is not for the faint hearted. For a fully flexible system, I will probably add the 28/4.5 lens, which will bring the system price to S$90,000. This is a full professional system, which requires that the photographer operating the camera is competent, and knows exactly what he is doing. It requires for him to slow down, and be methodical in his work. But when he gets it right, the resultant image is beyond anything else in the market. And truly the BEST OF THE BEST.