Is Steve Hopf still active?

[Jay Wolfe]

Wow, missed this entire thread

I like my DIY GG, so easy and fun

Bought a Satin Snow and several Hopf, even a Boro

Another useless post!

Have fun guys, for tomorrow we...

Another useless post.

[Drew Wiley]

What's useless about it? If Steve is out of business, and one does have a sample of his GG, or that of one the other successful makers mentioned here, that would give a helpful visual clue how to specifically grind their own, to what degree. (Another useless complaint)

[Bob Salomon]

What's useless about it? If Steve is out of business, and one does have a sample of his GG, or that of one the other successful makers mentioned here, that would give a helpful visual clue how to specifically grind their own, to what degree. (Another useless complaint)

A friend of mine used to take a soft cloth and a tube of toothpaste and use them to polish gg to make them very bright.
At the same time I used to varnish my Sinar gg in my studio in the 60s to make them much brighter. But the varnish would yellow and had to use a solvent to clear it off and revarnish every year or so.
Still prefer the proper Fresnel though.

[denverjims]

A friend of mine used to take a soft cloth and a tube of toothpaste and use them to polish gg to make them very bright.

So, that's why they make the whitening type of toothpaste?

With apologies, Jim

[Drew Wiley]

I prefer fluoride toothpaste to make the glass more resistant to scratches. It also makes things nice and minty underneath that sweaty darkcloth. On a more serious note, I was recently sorting out my little stack of 4x5 GG's and discovered I actually had one of the old varnished Norma ones. I installed it out of curiosity, and it certainly was dimmer (and yellower) than the later Sinar ground versions. I removed it the same afternoon. Lesson learned. Bob S. once talked about the coating method of mfg a GG; but this was my first encounter with one, and not a happy encounter. Perhaps if you're listening in, Bob, what was the kind of glass that would have come with my brother's Super Technika, last version (V?- not a Master T.). I was just little kid when I tried to view through that thing via a hood.

[Bob Salomon]

I prefer fluoride toothpaste to make the glass more resistant to scratches. It also makes things nice and minty underneath that sweaty darkcloth. On a more serious note, I was recently sorting out my little stack of 4x5 GG's and discovered I actually had one of the old varnished Norma ones. I installed it out of curiosity, and it certainly was dimmer (and yellower) than the later Sinar ground versions. I removed it the same afternoon. Lesson learned. Bob S. once talked about the coating method of mfg a GG; but this was my first encounter with one, and not a happy encounter. Perhaps if you're listening in, Bob, what was the kind of glass that would have come with my brother's Super Technika, last version (V?- not a Master T.). I was just little kid when I tried to view through that thing via a hood.

Just an older version of their gg. Current ones are much brighter and their current Fresnel is as well.

[Tin Can]

The KMV GG are the most interesting, a coating

I have it in 5X7 and 8X10, no way to clean the ground side...

Is there?

I love the aerial view slices!

[Vaughn]

Add me to the list that dislike frensles...or how ever it is spelled. For the same reasons of the OP and others. Don't need them either -- I can always see what is on the GG. And the the drop-off is not an issue if you place your eye in the path of the light hitting the GG.

[John Layton]

I read something recently about fresnels...perhaps on this forum...that as the degree of rear tilt increases - the accuracy of focus, starting at the periphery of the image, becomes very slightly suspect (likely mitigated if the lens is stopped down - but still). In other words, there is an effective focus shift - not in the lens, but in how the fresnel field is interpreting focus as the focal plane rotates. I also believe that there was some mention of this phenomenon being more pronounced with wide and super wide lenses, and perhaps hardly noticeable with longer focal lengths.

I wouldn't have brought this up - and believe me, I dearly love my Maxwell screens (worth every hard-earned cent!) - but there is an image which I made awhile back using my Maxwell-equipped 5x7 and a 90mm lens (super wide-ish for the format), set at a fairly extreme degree of rear tilt (rear because I did not want to lose coverage and could not shift front enough to compensate for front tilt) - and yet to my eyes the focus was spot-on to the edges of the field. Took several frames, re-checking before each frame. Processed images visibly soft near peripheries. So?

Actually, this makes intuitive sense...but I still cannot fully wrap my head around this. Anything to it? Bill Maxwell would know...maybe I'll try contacting him.

[Bob Salomon]

I read something recently about fresnels...perhaps on this forum...that as the degree of rear tilt increases - the accuracy of focus, starting at the periphery of the image, becomes very slightly suspect (likely mitigated if the lens is stopped down - but still). In other words, there is an effective focus shift - not in the lens, but in how the fresnel field is interpreting focus as the focal plane rotates. I also believe that there was some mention of this phenomenon being more pronounced with wide and super wide lenses, and perhaps hardly noticeable with longer focal lengths.

I wouldn't have brought this up - and believe me, I dearly love my Maxwell screens (worth every hard-earned cent!) - but there is an image which I made awhile back using my Maxwell-equipped 5x7 and a 90mm lens (super wide-ish for the format), set at a fairly extreme degree of rear tilt (rear because I did not want to lose coverage and could not shift front enough to compensate for front tilt) - and yet to my eyes the focus was spot-on to the edges of the field. Took several frames, re-checking before each frame. Processed images visibly soft near peripheries. So?

Actually, this makes intuitive sense...but I still cannot fully wrap my head around this. Anything to it? Bill Maxwell would know...maybe I'll try contacting him.

As Mr Trump says, fake news. The Fresnel, a photographic one of proper focal length does not displace the gg image at any degree of tilt/swing/rise/fall on any camera.

What you might experience is blacking out of the image as you do camera movements if your eye does not remain on the optical axis. This means that on some enhanced brightness viewing systems you may have to tilt your loupe to keep it on the optical axis. Sinar used a tilting mirror in their bino reflex hood to do this.