XT RODENSTOCK 23MM F/5.6 IN-DEPTH REVIEW

PhaseOne XT & Rodenstock HR 23mm

THE WIDEST LENS ON THE MARKET FOR FULL-FRAME MEDIUM FORMAT: PHASE ONE XT RODENSTOCK 23MM F/5.6 IN-DEPTH REVIEW!

Also available for various other technical cameras, this is currently the widest lens for any full-frame medium format system on the market: see in this Phase One XT Rodenstock 23mm f/5.6 in-depth review my thoughts about this incredible optical feat and why this lens is so important for me and my work!

As a landscape and architectural photographer, I love wide & ultra-wide-angle lenses both for the expressive and interpretative opportunities they offer, and for the possibilities they open technically in terms of being able to craft images otherwise impossible to create.

In fact, the very existence of the Phase One XT Rodenstock 23mm f/5.6, covering an incredible angle of view of about 110 degrees on a full-frame medium format sensor (112 degrees when fully shifted), has been one of the most compelling reasons for me to move back to technical cameras and to the Phase One XT (see SIMPLY REVOLUTIONARY: A PHASE ONE XT REVIEW).

Before we start, let me remind you that, as always, this review is based on real use of the lens in the field, and while you’ll find controlled tests, you won’t find any charts or studio shots in it. As well, please keep in mind that all my reviews are made under the point of view of a Fine Art Landscape Photographer: if your genre of photography is different, my findings might not apply to you and your work.

Disclaimer: At the time of writing, I am a Phase One Ambassador. That said, I am a professional photographer looking for the best equipment for my work, I buy all my gear with my hard-earned cash, and I don’t get paid by anyone to write articles for my blog.

When Phase One released the XT, I immediately loved the concept. The idea of being able to use the amazing Rodenstock lenses with the 150 MP Phase One IQ4 back on a small and portable tech camera body with full digital integration was impossible to resist, and my experience with the Phase One XT Rodenstock 23mm f/5.6 didn’t disappoint. Due to the well-known pandemic, besides my testing I could only enjoy the lens during one outing so far, but even in the short time I worked with it, this lens deeply impressed me.

This article is the first of a series of four articles dedicated to Rodenstock lenses on the Phase One XT. Below, a list of all articles in this series:

PHASE ONE XT RODENSTOCK 32MM F/4 IN-DEPTH REVIEW
PHASE ONE XT RODENSTOCK 50MM F/4 IN-DEPTH REVIEW (coming soon)
PHASE ONE XT RODENSTOCK 90MM F/5.6 IN-DEPTH REVIEW (coming soon)

Let’s get started now and see in this Phase One XT Rodenstock 23mm f/5.6 in-depth review if it delivers!

The Dolomites Photography Workshop

BUILD, SIZE AND WEIGHT
The Phase One XT Rodenstock 23mm f/5.6 is built like a tank, featuring a very compact body for such an ultra-wide, full-frame medium format lens. The main physical difference between getting this lens in Phase One XT mount vs getting it in Rodenstock Aperture Mount (or, if you can find it, in Copal 0 shutter), is in the protruding X-Shutter.

The X-Shutter gives you full control of aperture and shutter speed directly from the IQ4 digital back in exchange for a weight penalty of about 200/250 gr (0,4/0,5 pound) against the same lens in Copal 0 or Rodenstock Aperture Mount. I really enjoy having such integration, and I am happy to carry a little extra weight in exchange for that.

In X-Shutter version, the lens barrel features just a focus ring, which Phase One calls “Ultra Fine Manual Focus”. The action of the ring itself is extremely smooth, and the focus throw is extra-long to ensure very precise focusing. Two finger tabs are available to help you rotate the ring, something I found very handy given the small size of the lens and the ring’s position very close to the camera body.

Minimum focusing distance for the Phase One XT Rodenstock 23mm f/5.6 is unmarked but taking the last marking at 0.25m I estimate it to be around 0.2m.

Like all tech camera lenses, the Phase One XT Rodenstock 23mm f/5.6 is not weather-sealed. Since I often use my gear in adverse weather conditions, I always carry a Think Tank Photo Emergency Camera Cover which works great in protecting the camera and the lens from the elements, while allowing me to operate them normally under it.

Precise focal length of the Phase One XT Rodenstock 23mm f/5.6 is 23.82mm. With its 95 x 107mm (3.74 x 4.21 in) size and 850 gr (1.87 lbs) weight, with a filter thread of just 72mm, and with a FOV equivalent in 35mm full-frame terms of around 15.5mm, the Phase One XT Rodenstock 23mm f/5.6 is not only the widest lens for any medium format system but is also quite small and light for what it does.

For comparison, in the small medium format arena the Hasselblad XCD 21mm f/4 is 83 x 106mm, has a 77mm filter thread and weighs 600 gr; the Fuji GF 23mm f/4 is 89.8 x 103mm, has an 82mm filter thread and weighs 845 gr; the Leica 24mm Super-Elmar-S f/3.5 is 101 x 112mm, has a 95mm filter thread and weighs 1260 gr. In the full-frame medium format camp, Phase One’s own 28mm f/4.5 is 90 x 136mm, has no filter thread (you need to either use rear gelatine filters or use 150mm filters with special holders) and weighs 1100 gr; the Hasselblad HCD 24mm f/4.8 is 100 x 99mm, has a 95mm filter thread, and weighs 810 gr.

Cinque Terre & Tuscany Photography Workshop

USE OF FILTERS
Thanks to the Phase One XT Rodenstock 23mm f/5.6’s 72mm filter thread, I can use 100mm filters with it, with no issues whatsoever.

After almost 5 years working with Formatt-Hitech filters as a Brand Ambassador & Featured Artist (09.2016-05.2021), I am now looking for new filters to help me create my Fine Art landscape photographs. I am currently testing various options, and will update you as soon as I’ll have found the best, highest quality solution for my work.

IN USE: FOCUSING AND DIAPHRAGM
Like all tech camera lenses, the Phase One XT Rodenstock 23mm f/5.6 is manual focus only. For my Fine Art landscape work what counts the most, more than having the convenience of autofocus, is focusing precision. A very long focus throw, together with the Phase One IQ4’s powerful magnifying features, makes achieving precise focus extremely easy.

The Phase One XT Rodenstock 23mm f/5.6 comes equipped with Phase One’s revolutionary X-Shutter. The X-Shutter electronically controls both diaphragm and shutter, allowing for full integration with the Phase One IQ4 either directly – when using the lens with the Phase One XT – or via a cable if you use any other lens mount supporting X-Shutter. In particular, this means that your aperture and shutter speed can be controlled via the IQ4’s touchscreen in all shooting modes supporting such controls, and that EXIF will automatically be populated with your shooting data.

SHARPNESS AT INFINITY
Methodology: using my usual “real world” test scene, I manually focussed the lens on the trees on the far ridge in the center of the frame, using the maximum focus area magnification for precise focus, with the lens wide open. I then prepared 900 x 600px, 100% crops of the center, the top left corner and the mid-right side of the frame at full-stop apertures ranging from wide open to f/16. My Phase One XT had Firmware 8.01.0 installed. Capture One Phase One XT Rodenstock 23mm f/5.6 lens profile has been applied, and a LCC profile has been created and applied to eliminate vignetting and colour cast.

Let’s start looking at the full scene first, to see how much coverage a 110 degrees angle of view will give you in the real world. The red rectangles mark the locations of the crops (click on the image to enlarge):

Let’s now examine the crops in detail, starting with the center of the frame (click on the images to enlarge):

Sharpness in the center is most impressive: the Phase One XT Rodenstock 23mm f/5.6 starts razor sharp wide open, where it performs at its best. Sharpness gently declines until f/16, where diffraction is visibly taking its toll. For work where sharpness in the center is critical, I’d happily use the lens wide-open, with f/11 being the smallest aperture I would use, if and when necessary.

Let’s now examine the mid-right side of the frame (click on the images to enlarge):

In the mid-right of the frame, the Phase One XT Rodenstock 23mm f/5.6 outputted a very good performance wide-open, improving at f/8 where the lens is at its best. Performance at f/11 is very similar to f/8, while at f/16 diffraction’s effects start to be clearly visible.

Finally, let’s check the top left corner (click on the images to enlarge):

In the top left corner, the Phase One XT Rodenstock 23mm f/5.6 is softer wide-open than it is over the rest of the frame, and some astigmatism seems to be present. Stopping down dramatically improves the situation; at f/8 the lens starts to come into its own, and f/11 is definitely the best aperture in this area of the frame. At f/16, as expected, diffraction starts to take its toll.

Normandy & Brittany Photography Workshop

SHARPNESS AT CLOSE FOCUSING DISTANCE AND BOKEH
To examine sharpness at very close focusing distance, as well as to see how the Phase One XT Rodenstock 23mm f/5.6 draws out-of-focus areas, I focused on the Phillips screw right under the mailbox’s red flag in the lower right corner of the frame. Together with the full frame image I included 900 x 600px, 100% crops taken at the point of focus, to check out sharpness, and near-center crops to see how the lens behaves in out-of-focus areas near infinity. Again, Capture One Phase One XT Rodenstock 23mm f/5.6 lens profile has been applied, and a LCC profile has been created and applied to eliminate vignetting and colour cast.

Let’s see the full image first, again to see how wide a 110 degrees angle of view is in the real world, as well as to show you the locations of the crops (click on the image to enlarge):

Let’s now examine sharpness at the point of focus (click on the images to enlarge):

In this torture test, the Phase One XT Rodenstock 23mm f/5.6 showed an extremely good performance focused up close in the far lower corner of the frame. The lens starts a bit soft wide-open due to what looks again like astigmatism; stopping it down, the lens quickly comes into its own. Best performance is at f/11, while, as expected, apertures smaller than f/16 clearly suffer from diffraction.

Let’s see now how the Phase One XT Rodenstock 23mm f/5.6 renders out-of-focus areas at far distances in the center of the frame (click on the images to enlarge):

While a 14-15mm FOV equivalent ultra-wide lens with a maximum aperture of just f/5.6 would not be my first choice to create bokeh, the Phase One XT Rodenstock 23mm f/5.6 paints out-of-focus areas beautifully wide open, with a smooth, soft rendition that is never mushy. Stopping down, the lens slowly and gracefully gains sharpness with each stop, while keeping what I consider to be a beautiful rendition of OOF areas.

On a side note, it is interesting to keep in mind that when using a camera with such a large sensor even an ultra-wide-angle lens such as this offers much less depth of field than what you’d expect from a 14mm on a 35mm full-frame camera. Therefore, if you focus the Phase One XT Rodenstock 23mm f/5.6 at close distances, don’t expect to get everything in focus from close-up to infinity, even stopping the lens down to f/16. If you need everything to be perfectly in focus all over the frame in near-far compositions, you’ll need to either use hyperfocal distance or to carefully place your focus point in your frame; in extreme cases, resorting to focus stacking might help.

Death Valley Photography Workshop

SHIFT AND FULL SHIFT STITCH
The ability to shift is one of the main reasons to choose a tech camera for your landscape and architectural work. Shift is useful to straighten converging lines when pointing the camera off level, of course, but is also useful to create images via stitching that would cover a wider angle of view than what using the lens unshifted would provide.

The Phase One XT Rodenstock 23mm f/5.6, thanks to an image circle of just 70mm, when used on a full-frame medium format sensor such as the IQ4’s only allows for about 2mm of shift in either direction before starting to show hard vignetting. While this limits the amount of correction possible as far as horizontal & vertical shift go, to me there still is a point in using shift to create a stitched, larger image with this lens, when needed, to put the whole 112 degrees of coverage the lens can offer at infinity to a good use. This is especially true if you plan on using a different crop than the native 4:3 offered by the Phase One IQ4.

To visually show you what I mean, I created two composite images, one at infinity and one at close focusing distance, stitching four single images taken with the back fully shifted in all directions (12/12mm, -12/12mm, 12/-12mm, and -12/-12mm). I’ll use these images here both to show you all the most common image ratio crops together with their resulting resolutions in Mp, and to check on the Phase One XT Rodenstock 23mm f/5.6’s sharpness when shifted.

Let’s start having a look at the full image at infinity with crop overlays (click on the image to enlarge):

Below you’ll find a list of the resolution resulting from stitching & cropping against the resolution you’d get cropping just a single shot, for each image ratio, in descending order of “gain”. Stitched images on the left side, cropped single files on the right side:

1:1 | 13000 x 13000px = 169 Mp versus 10652 x 10652px = 113 Mp (+56 Mp)
16:9 | 16178 x 9100px = 147 Mp versus 14204 x 7990px = 113 Mp (+34 Mp)
3:2 | 15180 x 10120px = 153 Mp versus 14204 x 9470px = 134 Mp (+19 Mp)
5:4 | 14230 x 11204px = 159 Mp versus 13318 x 10652px = 141 Mp (+18 Mp)
4:3 | 14700 x 11025px = 162 Mp versus 14204 x 10652px = 151 Mp (+11 Mp)

As you can see, the increase in resolution and in coverage gained by stitching four fully-shifted images vs cropping a single shot is dramatically evident if you plan on cropping your image to 1:1, where you’ll gain over 50 Mp and quite a bit of coverage, slightly less so for 16:9, even less so for 3:2 and 5:4, and of course it will be the least evident if you plan on staying with the native 4:3 image ratio.

Iceland Photography Workshop

SHIFTED SHARPNESS
Gaining coverage and resolution is all well and good, but it would be for naught if the resulting images were of lower quality than what you’d get without stitching. Creating samples to check sharpness for every shifted position at every aperture would make the review impracticably huge, and it would be a bit redundant as well. To give you an idea about how the lens behaves when stitched, I decided to add samples taken at three different positions at infinity and one at close distance. These samples have been shot at f/11, which to me is the aperture offering the maximum overall average sharpness over the frame. As always, Capture One Phase One XT Rodenstock 23mm f/5.6 lens profile has been applied, and a LCC profile has been created and applied to eliminate vignetting and colour cast from each of the four images before stitching them.

Let’s see the full images first, both at infinity and close focused, to show you the locations of the crops. Please also note how, at close focusing distances, the different magnification results in a slightly larger image circle and, therefore, in a little more room for shift – albeit with the presence of blue/yellow colours rings at the extreme of the image circle as well (click on the images to enlarge):

Let’s now examine the crops, starting with the three infinity ones followed by the close focused one (click on the images to enlarge):

Starting with the infinity crops, as you can see, at f/11 sharpness in the center of the frame is extremely high, whereas in both far corners – with the lens fully shifted in opposite directions – the samples are slightly less sharp but perfectly useable for any kind of work.

Coming to the close focus crop, considering that we are at the limit of the lens’ image circle and at very close focusing, the Phase One XT Rodenstock 23mm f/5.6 did a great job in retaining detail.

Glencoe & Isle of Skye Photography Workshop

SHARPNESS CONCLUSIONS
First, to put the results in perspective, let’s remember that the Phase One XT Rodenstock 23mm f/5.6 is an extreme wide-angle, it needs to cover a very large 53,4 x 40mm sensor and it must resolve a pixel size of 3,76 micron. To give you an idea, 50 Mp small medium format sensors are both smaller at 44 x 33mm and have a larger pixel size of 5,3 micron. Currently, the only other sensors featuring a pixel size of 3,76 micron are 100 Mp small medium format and 61 Mp 35mm full-frame sensors, but their sizes are respectively just 44 x 33mm and 24 x 36mm. Having to cover such a large image area while providing such a high level of resolving power over the whole frame, is a tall order for any lens.

The Phase One XT Rodenstock 23mm f/5.6 succeeds in this feat brilliantly. Focused at infinity, sharpness in the center of the frame is unbelievable wide-open and keeps to fairly exceptional levels until f/16, when diffraction starts affecting the results. In the far corners, some astigmatism causes performance to degrade wide-open, but as soon as you stop the lens down one stop, image quality improves dramatically; best overall aperture for sharpness all over the frame when photographing a flat target at infinity is f/11.

At close focusing distances and focused in the corner rather than in the center of the frame, the lens behaves slightly better than at infinity wide-open and is perfectly useable between f/8 and f/16, where diffraction takes its toll.

If interested, you’ll find Rodenstock own lens data and MFT charts here: LENSES FOR DIGITAL PHOTOGRAPHY.

Considering the kind of composition that I normally use when creating my Fine Art Landscape photography work, which are generally near-far and not always with the horizon parallel to the focus plane, I expected the Phase One XT Rodenstock 23mm f/5.6 to be a great performer in terms of sharpness all over the frame, and my expectations have been confirmed by my use of the lens in the field during my first outing with it.

LCC OR NOT LCC: VIGNETTE, COLOUR CAST AND COLOUR RENDITION
As to be expected with such an ultra-wide, tech-camera lens, the Phase One XT Rodenstock 23mm f/5.6 features some very visible, soft-vignette all along the aperture range. While I haven’t measured it scientifically, it feels like vignetting is a little over two stops. If you want to get rid of it, a possible solution is to get a center filter; these aren’t easy to find, besides being quite expensive. As well, if you plan on using other filters with this lens, adding a center filter before those would ironically cause hard vignetting, which kind of defeats the purpose.

On the other hand, if you don’t mind a software-based solution, creating an LCC profile (see CREATING A LCC REFERENCE IMAGE for a good tutorial about it), using the appropriate white target provided by Phase One with the XT, does solve the problem of vignetting beautifully. Not only this is free and won’t create any problems if you plan on using filters with your Phase One XT Rodenstock 23mm f/5.6, but it will also give you the possibility to fine tune the amount of vignetting correction any way you like. Thanks to the new IQ4’s sensor, crucially, using a software-based solution to fix vignette comes with no penalty in terms of noise or image quality degradations of sort.

Colour cast is a traditional issue with tech camera wide-angle lenses and digital backs. While the IQ4 is light years better than the older backs I used back in the day (P45+, P65+ and Leaf Aptus 12R), with such wide angles as the Phase One XT Rodenstock 23mm f/5.6 some colour cast is still visible. While a center filter wouldn’t help at all with this issue, creating an LCC profile for the lens will perfectly solve the problem with a click.

To show you both issues, and how creating an LCC works to solve them, I created two sets of images taken respectively wide-open at f/5.6 and at f/11, my working aperture with this lens. I then prepared them with and without an LCC profile applied for you to gauge the differences (click on the images to enlarge):

As you can see, the LCC profile completely solves both the vignette & colour cast problems, making the decision to go with LCC profiles a no-brainer for me.

Once vignetting and colour casts have been taken care of, the Phase One XT Rodenstock 23mm f/5.6’s colour rendition is beautiful to my eye, balanced and with great tonal transitions, offering me a wonderful starting point for my post-processing.

DISTORTION
To check for distortion, I photographed my uninspiring garage door, which straight metal lines provides me with a perfect test scene for a distortion test. For your convenience, to help you check distortion easier I slightly increased contrast, added straight red lines in PP, turned the image horizontal and cut the frame in two, showing you just the top half of the frame. Phase One XT Rodenstock 23mm f/5.6’s profile has been applied in Capture One. Let’s see the results (click on the image to enlarge):

As you can see, the Phase One XT Rodenstock 23mm f/5.6 with its lens profile applied is extremely well controlled for distortion: straight lines stay perfectly straight all over the frame.

FLARE AND CHROMATIC ABERRATIONS
When I am working in the field, since I almost inevitably have a filter holder on the lens, I never use a lens hood. Since I want my lens tests to mimic my working conditions as closely as possible, during my tests I never use a lens hood as well. In the test image below, I included the sun in the frame, keeping it close to the image’s corner. As well, I included a crop of the area surrounding the sun to check for contrast and chromatic aberrations (click on the images to enlarge):

Rodenstock lenses are traditionally prone to flare, and the Phase One XT Rodenstock 23mm f/5.6 is no exception: you can clearly see loss of contrast and variously coloured ghost images appearing in the frame. On the other hand, the lens shows no CA of any kind, and the loss in contrast visible around the sun is easily fixed in post-processing.

Since I never use any lens hoods when I work, as mentioned above, to prevent my lenses from flaring I always carry with me a foldable, reflector-like grey card which doubles perfectly as a “sun blocker”. It’s small, light, works perfectly in eliminating flare and doesn’t prevent me from using filters when I need to do so.

CONCLUSIONS
As I write this Phase One XT Rodenstock 23mm f/5.6 in-depth review, this is the widest lens for full-frame medium format cameras and, to me, is a must-have for the ultra-wide loving landscape photographer using a tech camera system. The lens is small and light for a full-frame medium format lens, features the revolutionary X-Shutter and is fully integrated with the Phase One XT, making it a joy to use in the field compared to using tech cameras without X-Shutter.

Under a technical point of view, the Phase One XT Rodenstock 23mm f/5.6 is an extremely strong lens, used within its limitation. For my work, this means using it between f/8 and f/11 for optimal sharpness all over the frame. The amount of detail that this lens outputs, when paired with the Phase One IQ4, is simply astounding; distortion is all but absent and so is chromatic aberration.

Is the lens perfect? No, nothing is. Flare can definitely be a problem when shooting into the sun, and you’ll need to shade the lens when doing so to prevent it from happening. Vignette is very present, and it’s up to you to decide whether you prefer to fix it via a center filter, via LCC or just leave it in for artistic purposes. While minor, colour cast is visible with this lens, and I recommend you correct it via an LCC profile, which takes all two seconds to create and apply. That said, all these shortcomings are easily solved, and once you did that the Phase One XT Rodenstock 23mm f/5.6 is a truly magnificent performer.

The artistic rendition of any lens is a very personal matter, of course. Personally, I find the Phase One XT Rodenstock 23mm f/5.6 to be a beautifully drawing lens, with great character and pleasant out-of-focus areas.

The Isle Of Arran Photography Workshop

A MUST-HAVE LENS? THOUGHTS ON THE FOCAL LENGTH
The choice of focal lengths for our cameras heavily influences the aesthetics of our work and therefore is an extremely personal matter, one where there is no right or wrong – just different tools for different artists. As I mentioned at the beginning of this article, I love ultra-wide lenses. For me to even consider any camera system, it needs to offer at least a native option covering 100-110 degrees of field of view (or to allow for adapting a third-party solution that does so), and the Phase One XT Rodenstock 23mm f/5.6 perfectly fits the bill.

If you are fine with a slightly longer lens, Phase One offers a XT-native 32mm alternative, also in X-Shutter (the focus of my next review); more, there are other 28mm alternatives from Rodenstock and, if you can find it, from Schneider without X-Shutter.

So, should you get it? Well, as always it depends on your preferences in terms of focal lengths. If, like me, you love to use ultrawide-angle lenses and you are using – or planning on using – a tech camera, this lens is a must have. In case, I would heavily recommend you get the lens in X-Shutter, for the full integration it provides, in particular when used on the Phase One XT.

In conclusion, I loved the Phase One XT Rodenstock 23mm f/5.6, it’s optically wonderful and if you need this focal length on a tech camera there is nothing out there like it. Highly recommended.

As always, the photographs are what counts the most. Due to Covid-19, I haven’t had a chance to use this lens intensively yet; I will post samples taken with the Phase One XT Rodenstock 23mm f/5.6 as I’ll develop them.

Dorset Jurassic Coast Photography Workshop

Thanks for reading this Phase One XT Rodenstock 23mm f/5.6 in-depth review, I hope you enjoyed it! Why don’t you share it with your friends, or drop me a comment to let me know how you feel about this?

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