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Thread: Experience with the new Linhof bright ground glass?

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    Experience with the new Linhof bright ground glass?

    I'm considering to put an order for the new bright ground glass. It is an expensive product though and I'd like to hear some experience from those that have used it.

    I'm not worried about it not being bright enough (seen photos), I'm not even worried about resolution (not seen photos, but if it works with the new 12x it should work with my 20x), however I've heard that at least one user had problem with focus shift. That's more worrying.

    Is it supposed to be fully compatible with the standard Linhof sliding back (mine is probably manufactured 2010), so it's just drop it in? Or will I have focus shift issues?

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    Re: Experience with the new Linhof bright ground glass?

    I've communicated at length with Paula at Linhof Studio and she reckons it's better in every way to the old bright acute matte screen. Perhaps she wouldn't offer such information volunteeraly but in my experience she had always been open and honest, almost to a fault about gear she sells.

    The focus shift you mention, is it because of a difference in the position of the gg plane? If so, it could be calibrated I guess, although at some hassle. I have heard the new gg gas more "snap" of in and out of focus. In this case it might be possible it is actually showing the true focus plane more accurately and more consistantly where the older gg masked some user error in both directions (front and back focus)?

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    Re: Experience with the new Linhof bright ground glass?

    I have now a Linhof Bright Screen on order. Damn it's expensive! I will eventually make a thorough test and comparison with the standard ground glass and post my findings.

    (I did not get the new Silvestri 12x loupe though, my current 10x and Belomo 20x will have to do)
    Last edited by torger; 26th June 2013 at 03:56.

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    Re: Experience with the new Linhof bright ground glass?

    Awesome! Looking forward to reading your impressions. I'd love to get it for myself, although the Silvestri screen I use is already pretty good. I imagine the new Linhof version must be amazing to justify the price.

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    Re: Experience with the new Linhof bright ground glass?

    Had a visit to Paula. Very nice shop. Sorry - didn't see the new GG.

    Looked at the Silvestri sliding back (very well made); their 12X loupe is a joy and highly recommended.
    www.gigi-photos.com
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    Re: Experience with the new Linhof bright ground glass?

    You'll have to wait for my report, as UPS took it reaaaaaally slow to get the package from Great Britain to Sweden, and on the way from south to north in Sweden (where I am) they lost it somewhere, so it's gone. Sigh... oh well, with some luck they'll find it but I guess there will be quite some time before I actually get my paws on the ground glass.

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    Re: Experience with the new Linhof bright ground glass?

    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.
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    Re: Experience with the new Linhof bright ground glass?

    Brilliant info, thanks so much for posting this!
    It seems that while not "perfect", this new screen would be a major improvement for me except for one crucial thing: It's only 6x6cm and I shoot 6x7cm film...
    I don't shoot with anything longer than 90mm so the dimmer longer focal lengths wouldn't bother me, but when I shift to digital capture (dreams are free!) I'd go no wider than 35mm, possibly even 40mm. Sounds perfect for my use case.

    PS: Torger, are you still shooting with your fussy Leaf? Did you end up buying a new back or are you still fighting the good fight?

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    Re: Experience with the new Linhof bright ground glass?

    Yes the glass is a good product, the buzz around it may have raised expectations to unrealistic levels though. I'm certainly satisfied. The glare made me a bit disappointed though as I hoped it would be better without focusing cloth / lid. With the old glass I only use the cloth with the 47 and 35 normally, and if it was not for the glare I could probably drop the cloth for the 47 now. I'm thinking of looking for some anti-glare film.

    Yeah, I'm using my Leaf, I like it when it works and summer is easy on it. It's going back to the factory again though sometime next week. There's will at Leaf to fix the problem but there's problems with the support organization, you have to nag and nag to get things happen. For a professional I see no other option that you must have a backup back or special warranty that guarantees replacement back, since if/when you get problems with your back it can be months and months before you have it corrected. I first contacted Leaf in September 2012 for this problem... it would probably have been a bit quicker if I had nagged a bit more, but I have a daytime job that takes a lot of time in periods so I haven't had the time and energy to push more. That it's so hard to get support I think is a receipe for getting people to leave the format, so I think they should be more serious about it.

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    Re: Experience with the new Linhof bright ground glass?

    Here's the review with images

    Review: Linhof Techno
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    Re: Experience with the new Linhof bright ground glass?

    To be honest, the pictures of the new screen look dramatically better than the old but for the dimmer 120mm example. If this was a 6x7cm screen, I'd get one in a heartbeat.
    Great job on the review!

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    Re: Experience with the new Linhof bright ground glass?

    Thanks. It would be great to be able to compare it to Kapture Group's sliding back with maxwell optics bright screen, but I don't have access to one. With that comparison I could give the ultimate consumer information :-). I have my suspicion that KG sliding back with glass is at least almost as good at a much smaller price. But I started out with Linhof original and when you already have the sliding back upgrading the glass is a nice thing to do.

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    Re: Experience with the new Linhof bright ground glass?

    Oh, after a day out with it I can say I really enjoy the brightness improvement on the 47 and 35. The view camera experience is certainly better with this type of glass.
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    Re: Experience with the new Linhof bright ground glass?

    Quote Originally Posted by torger View Post
    Thanks. It would be great to be able to compare it to Kapture Group's sliding back with maxwell optics bright screen, but I don't have access to one. With that comparison I could give the ultimate consumer information :-). I have my suspicion that KG sliding back with glass is at least almost as good at a much smaller price. But I started out with Linhof original and when you already have the sliding back upgrading the glass is a nice thing to do.
    I replaced the Acute Matte Screen (AMS) with a Bill Maxwell one - there's a slight improvement, but it's subtle. In terms of improvement 1.5 - 2 stops is what I figured I got with the AMS and Maxwell, so not a whole lot different from the new Linhof Brightscreen. The new Linhof screen sounds easier to clean however, since the fresnel is sandwiched between glass - which is nice - and the redesigned top looks like it will keep light out. The original AMS is reflective, but not so much that it ever bothers me. That said, I tend to use it with a Hasselblad RMFx viewfinder, which probably helps.

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    Re: Experience with the new Linhof bright ground glass?

    After some use I've got a bit use to the glare and I can "see through it" in many cases. I may still try to attach a anti-glare film like 3M armr200 and see if it works. Anti-glare films may interfere with the resolution though...

    Light is kept out from the top, but not completely at the bottom so I have taped there, the leak is quite small though so it's not strictly necessary, I just like to have light tight.

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