UPS found the package eventually.
I will sooner or later publish on my web page with photos, but here's a preview of the review:
Review of the new Linhof bright ground glass
In July 2013 I bought the new bright ground glass which was announced at Photokina 2012. I've had my eyes on it since release, but as it's very expensive (about €700+VAT) I have used the standard ground glass plus fresnel I already owned until now.
The glass is mounted in a metal frame and the viewable area is 60x60mm. Three different scorings exist, for 49x37mm (P45+, CFV-50 etc), 56x36mm (Aptus-II 10) and 53.9x40.4mm (P65+, IQ260 etc). I have the 49x37mm version as I have a 48x36mm Dalsa sensor. Apart from the portrait/landscape outlines seen in the pictures there is very fine grid and a cross in center which is only visible in the loupe. There are no marks to support the stitching positions of the sliding back, which is not surprising as the stitched frame for a 49x37mm sensor gets 71x49mm, ie wider than the glass. The standard ground glass on the other hand covers the full opening, ie 76x82mm, so if you are shooting film larger than 6x6 or want full stitching coverage you need the standard ground glass. The 49x37mm version of the standard ground glass also has scoring for the stitching positions. Personally I like this smaller window, it's nice to see a little more around the sensor area but the extra surface provided with the standard glass is so huge I find it a bit distracting when composing with longer lenses.
It's a bit surprising that they do not have scorings for the entry-level 44x33mm sensor size (P40+, IQ140), but instead the odd 56x36mm and 49x37mm size, both which seems to be near being discontinued. However for us amateurs the 49x37 / 48x36mm will still be popular for a long time as it is very common in the second hand market.
When measuring the scorings I noted that the 0.7mm wide lines are drawn in the center of the actual 49x36.8mm frame (as the Kodak sensor size is). I would have prefered an exact outline, but corners will be slightly approximate anyway with the ground glass, and raw converters often crop a little too. So I don't worry much about having a slightly smaller sensor, I see the scorings as a very slightly too wide outline for mine.
The standard ground glass has the fresnel mounted in a separate slot in front, and I had it permanently mounted, there is no reason not to. The slots are open and there are light leaks which you need to cover with tape, ie not an elegant design at all. The new ground glass however sits in the first slot and covers the second with it's top lip, so it becomes light tight at the top, there is still a small leak at the bottom though (how hard can it be to make it light tight?). The light hood accessory fits nicely without light leaks. The bottom light leak is so small that taping is not really required but I will tape it anyway.
I have done a careful resolution and focus shift test as follows: I focused on a slanted ruler and used a second camera with a macro lens to photograph the actual ground glass at high magnification, and comparing that with the actual photo when sliding in the digital back.
Concerning grain size and resolution it is almost exactly the same as the standard ground glass, ie very good (for being a ground glass). The new ground glass is a little smoother (more uniform grain size) and possibly has very slightly higher resolution. I've heard some say that the new ground glass has better "snap", ie it's more clearly visible when things go in and out of focus as you turn the focusing wheel. After swapping in and out I'd say that the standard ground glass without fresnel is the snappiest, and with fresnel it gets a bit less snappier than the the new ground glass. But the new is still (very) slightly less snappier than the standard without fresnel. I think the reason is that a fresnel lowers local contrast slightly, more if scratchy.
To double check I also looked at macro photographs of the different ground glasses, if the new ground glass actually would be significantly snappier the out of focus areas would be more fuzzy and the in-focus sharper, but I could not see any such difference. If there are any differences they are very small.
The separate standard fresnel is plastic and will over time get scratches from the loupe viewing, and it is quite prone to gathering dust and particles too and the patterned side is hard to clean. This is significantly improved with the new ground glass, as the fresnel is integrated; the viewing side is smooth glass (not scratched easily I assume) and the image plane side is the finely grained surface, while the fresnel is inside the glass and thus the hard-to-clean pattern is not exposed. So I will not expect the same degradation over time as one can do with the standard fresnel. On the other hand it's not too expensive to buy a new standard fresnel when it has become too scratchy.
As the fresnel pattern is closer to the grain one worry could be that it would get within the loupe's depth of field and disturb the viewing, but with a 10x loupe or higher magnifcation it will not, so don't worry. The only interference is the possibly slightly lower local contrast which I think is a general tradeoff you do when you have a fresnel.
What about focus shift? For focus shift to be relevant it must be visible at the resolution the ground glass provides, ie you can never focus more precisely than what the ground glass can resolve. In my test setup I cannot see any shift difference between the two ground glasses, and they match the actual photo taken by the digital back, ie there is no detectable focus shift. Be aware though that ground glass focusing cannot be as precise as live view focusing due to limits in resolution, I would not recommend it for larger apertures than f/11. A detailed analysis on focusing precision is found in another appendix to the Linhof Techo review, it's made with the standard ground glass but as the resolution is the same with the new the same analysis applies.
Same resolution, no snappier, less viewing area, so what's the deal? Brightness is. Ground glass is well-known to be dim, and extremely dim with non-retrofocus wide-angle lenses. I have the Schneider Digitar 35mm, a symmetrical wide angle lens design and it's about as bad as it can get concerning dimness. The Rodenstock wides are more retrofocus and has one stop wider aperture and are thus brighter, but then also much more expensive, heavier and have a bit more distortion.
The fresnel is there to make the ground glass brighter through bending in light on the sides towards the viewer. I assume that integrating it into the glass reduces light loss compared to having a separate, but the key difference seems to be that the fresnel in the new ground glass is designed for shorter focal lengths.
In the center the light comes straight at you so both new and standard+fresnel are equally bright there, and approximately equally bright for all focal lengths (assuming same max aperture and no center filter). The difference is how strong falloff there is towards the corners where the light does not fall in perpendicularly, becoming worse with wide angles. Symmetrical wide angles have very high natural vignetting too (hence the use of center filters) and the fresnel cannot improve on that, just minimize further vignetting by trying to bend the light back to perpendicular.
I've tested the Schneider 35, 47, 72 and 120mm on a static indoor scene with standard (ie weak) indoor lighting, photographed the ground glass perpendicularly with a long lens and then compared brightness difference. I used RawTherapee to convert the raws so I could get a neutral exposure-correct output (not possible with most commercial raw converters) so I could make a fair comparison. I did not use center filters on the 35 and 47 which affects the look of the ground glass photographs (more vignetted) but not the measurements.
Here's the results: 35mm and 47mm about 1.6 stop brighter corner, 72mm about 2.0 stop brighter corner, 120mm about 1.2 stop darker(!) corner. I've heard things like "4 stops better" about this ground glass, but that is obviously false and I think it is physically impossible with that kind of improvement, unless you compare to the standard ground glass without fresnel but noone would use it like that for a wide angle lens. It's also interesting to note that it's darker for long focal lengths. You can't do magic and make a fresnel that is optimized for all focal lengths, so there is a tradeoff. Simply put the new ground glass is brighter for anything 100mm and shorter, while the standard+fresnel is brighter for 120 and up. The 72 is actually brighter than the 120 on the new ground glass. To make sure nothing really bad happens I put on a 180mm too and checked visually and it looks okay, probably a little darker than the standard but on this long lens the image does not really look vignetted so striving for the utmost brightness there is not the right design target to have anyway, the challenge to meet is with the wides, and there it provides an improvement.
I think many will consider the 1.6-2 stop corner improvement as quite moderate and was maybe expecting more. Does it provide any real advantage? Ground glass dimness is not an on/off problem, ie it's not either bright enough or too dark for any given condition. If shooting in a comfortable environment without stress you can almost shoot in the blind and still have an okay workflow. Outdoor in cold conditions, or with lots of mosquitos attacking you, or an uncomfortable camera placement will lower the acceptance of ground glass dimness. Sometimes I find myself recomposing with trial-and-error (shoot, look at back display, shift-adjust shoot again). This happens more often with dim wide angles, as you may have to move your head to impossible positions to be able to look into the corner. This will for sure still happen with the new ground glass, but less often.
Here's another way to look at it which makes the "moderate" improvement to look better: the 35mm on the new ground glass has actually a little brighter corners than the 47mm on the standard. And the 47 becomes brighter than the 72 was. So wide angle dimness issue is shifted up in focal length. I have quite many lenses in the system, but a favourite focal length of mine is the 47, and brightening that past the old 72 experience is worth it for me.
One notable drawback with the new ground glass is glare. It's practically a mirror, and it's really the only aspect of the product that made me a bit disappointed. The standard fresnel has glare too, but not as much. My layman guess is that a more efficient fresnel leads to more glare, so this is what you pay for wide angle brightness. However, for €700 I would expect some kind of anti-glare surface treatment, and as far as I can see this has none. I own but don't use the 4x loupe lid as 4x is not enough for critical focusing (so I would have to remove/reattach it all the time) and I have good enough eyes to do composing unmagnified. This means that glare is a problem, too much glare and I need to use the focusing cloth even if the image is bright enough. It does help to pull out the lighthood and put the face against it and cover as much as you can with your hands, but with the sun behind your back you still may need a focusing cloth. I need more field testing to know, but I think there will be some situations when I will due to this glare issue use the focusing cloth when I would not with the standard glass+fresnel. As an experiment I put an ordinary polarizing filter in front of the ground glass in such an impossible glare situation and then most glare disappeared and I could see the image. That cuts 1.5 stop of light though so it's not a real solution.
Let's summarize, this is what I like about this ground glass:
* Brighter corners on wide angles and normal lenses, without sacrificing too much on longer lenses, and no loss of resolution (traditionally brighter glass meant lower resolution).
* Brightness improvement may look only moderate on paper, but the dim Schneider 35mm becomes brighter than the 47 was on the standard, and the 47 brighter than the 72!
* Integrated fresnel, less prone to scratches and collecting dust.
* I like the smaller viewing window, less distracting when composing.
* Nicer finish and (almost) no light leaks (but I will tape anyway).
...and this is what you should have in mind if you consider upgrading:
* It's no magic bullet, wide angles will still be dim, you will still be using a focusing cloth (or other covering viewing aid) from time to time.
* The Linhof standard ground glass + fresnel is already quite good compared to the competition.
* The viewing area is significantly smaller and does not support stitching well.
* The corner improvement is no more than 1.6 - 2 stops and for 100mm+ there is actually a slight darkening of corners. If you have high expectations of brightness improvement this may not be enough to please you.
* The glare is worse, which can be disturbing if you like to view unmagnified without a covering viewing aid. Personally this is the only aspect that made me a bit disappointed.
* The resolution is almost exactly the same, and it's not easier to focus-peak ("snappier") than the standard ground glass, so there is no upgrade in that aspect.