After having spent more time this weekend playing with the Horseman LD with my D2x, here are some comments:
TEST SET UP
Lenses used: Mamiya 45 f2.8 for 645, and Schneider 110 mm XL 5.6 for LF,
Body used: Nikon D2x
LF camera: Horseman LD with F mount adapter,
- The unit is well built and as a consequence pretty heavy (around 4 kgs if I recall),
- It is rather bulky, and I would find it pretty challenging to pack the LD in my usual backpack for trekking without un-mounting the standarts. Need to think more on this,
- Mounting the d2x on the LD isn't that hard, but it takes a bit of practise before becoming able to do it quickly. Unfortunately, it appears to be impossible to mount the D2x on the LD when the RRS L bracket is in place because of an interference between the LD and RRs backets when mounting the body. I need to confirm this.
- Although the front and read standards are correctly calibrated vertically, it appears that the sensor of the D2x is not centered with a lens for which the front standard would have been set a zero (no lateral shift). There is a need to apply a 8-10 mm side shift to bring the lens center in alignement with the sensor center. Without doing this, vignetting appears faster on one side than on the other when doing lateral back shift.
- MF lenses are mounted thanks to a special metallic recessed board made available by Horseman in Mamiya and Hassy mounts,
- LF lenses on a Linhof lens board can be mounted readily to the front standard thanks to a Sinar to Linhof holder. The shape of this adapter appears to be such that the center line of MF and LF lenses are the same,
- When working with a lens like the Mamiya 45 f2.8 that I have tried, the applicable amount of tilt is very limited because of how close the DSLR is from the front standard. Typically only +/- 5 degrees in tilt. Down looking tilt of the rear standard (very rarely used for landscape) is almost impossible (2.5 degrees only),
- It is difficult to use the D2x in portrait mode because of an intereference between the support bracket of the LD, and the cable release connector. No problem if you don't use a cable release (but that is kind of mandatory I feel),
- Since there is of course no coupling between the lens and the body, you'll need to stop down the lens manually before shooting. Pretty usual stuff for LF shooters, easy to forget when you shoot with a DSLR...
- There is a need to focus MF lenses near infinity to be able to focus the whole thing at all, at least for wide lenses like the Mamiya 45 f2.8. Since the distance between the prism of the D2x and the front standart is only 2-3 mm when focused at infinity, it is better to adjust focussing using the lens focussing ring instead of standards movement. Indeed, it is very easy to move the rear standard too close to the front one, therefore causing the prism of the DSLR to touch the front standard, which induces an unwanted slight tilt... This might in fact only happen when applying an upward shift to the rear standard... go figure why some of your flat stitched images are suddenly blurred... :
It took me a while to figure out myself.
- Achieving critical focus proved to be easier than I had anticipated. At least, the results are sharp when the lens is stopped down to f11-f16,
- The main limitation is physical vignetting induced by the DSLR lens mount and internal structural elements and the LD's below itself. Lens image circle doesn't appear to be the limiting factor, even with MF lenses designed to cover 6*6. Even then, I got very good results with lateral shift
-- With the Mamiya 45 mm: up to +/- 20 mm and vertical shift up to +/- 10 mm (perhaps even a bit more),
-> This results in a perfect stitch that is about 10.000 pixels wide by 5000 wide in 8-images. These 8 images can be taken very quickly, I would say in 8 * (exposure time + 2 sec). There must be some light fall off towards the corners of the scene, but I didn't notice any with my test subject.
-- With a Schneider 110 mm: there is even a bit more room for shift, but I don't have the exact figures. The difference is not so big, and mostly result from the difference in size and location of the lens rear elements, not its image circle from what I could see.
- With both of these lenses, the resulting images are sharp, probably not 100% as sharp as those I get from my D2x with good old AFocused Nikkors at f11, but close enough to be very decent,
- Using the movements of the LD to increase DoF by using the scheimpflug rule is a lot more difficult than when working with 4*5 because of how small the DSLR viewfinder ends up being. The impact of subtle movements is very difficult to assess without taking a picture zooming at 100% on screen, which makes the process slow and cumbersome.
- Flat stiching using Stitcher 5.1 was OK, but a bug in the software prevented fully automated stitching. I had to use the semi automatic stitch mode, still fast, but not as fast as I would like.
Today, I still believe that cylindrical stitching with a good spherical head and PTgui has more future, but the LD's potential is starting to show.
I am actually thinking of writing a review covering this in more details.