How sharp can you get?

[Nathan Potter]

Mike, maybe. But don't jump to conclusions. Paul stated it nicely above - there's a lot of variables that affect image resolution in LF photography. Think of it as a photographic system not working for you but against you. Multiple variables may be involved in image degradation so you may need to go through at least all mentioned in this thread and eliminate them one by one to maximize your image quality.

I don't know the details of the screen you use but I tend to like a fairly finely ground one that may not be the brightest but has a bit better resolution of the image for a 5X loupe. Also doing that resolution test is a good idea if you really suspect your not capturing the plane of best focus with your film holders.

BTW someone mentioned above, or rather posed the question, "are all your photos of equally poor image quality". You might try to quantify this in order to unravel this detective story so to speak.

Nate Potter, Austin TX.

[Drew Wiley]

If you're technique is tuned in, there should be a dramatic improvement in quality
as you go up from 35mm to 120 film, from 120 to 4x5, and from 4x5 to 8x10. I can
shoot an 8x10 negative at f/64, which is hardly ideal for optimum lens performance,
and then even print it at f/64 with one of my less than best enlarger lenses, and it
will be a far more detailed image than any of my medium format prints in analogous
size. But you're only as good as your weakest link, whether on the camera or in the
darkroom. Filmholders or negative carriers which don't hold the film truly flat can
spoil just about everything. One nice thing about the larger formats is that you don't
generally worried about negative grain, and can opt for films with the best tonal range, edge acutance, etc. And a dust speck which resembles the Goodyear Blimp in medium format will be barely noticeable in 8x10. Size matters.

[Turner Reich]

I took my Shen Hao apart tonight and measured the thickness of the gg and the thickness of the wood that creates the standoff for the format, in this case being 4x5.

The thickness of the ground glass was all over the place, I'm going to put in the Satin Snow that I bought as an extra when I got the camera.

The thickness of the wood or the depth of the ground glass is also all over the place. It varies from .194.5 to .199. I measured it over and over, zeroing the Mitutoyo micrometer each time. If memory serves me the depth should be .197.

In this camera the ground glass is supported only on the long ends. Surprise surprise. Don't believe me, take out the ground glass and look. When the thin non-flat gg is placed on an end supported narrow support of wood and the the loupe is pressed on the glass for viewing it will flex. If the gg flexes will you get an accurate focus? If the gg is not in an accurate plane at the correct distance that correlates to the film holder depth will you get correctly focused images?

I had only used this camera once and the negatives were thin so I put them in a folder and hadn't looked at them until tonight. They are all out of focus, I use 5x7 and 8x10 all of the time and there is no problem with the other equipment and the holders I have used in a field camera that I built many years ago. I have also used them in a Toyo G and Calumet 400 4x5 so the holders are fine.

I will either have to make a new ground glass support or shim until the cows come home.

So the original post of "How sharp can you get?" is aptly appropriate for me.

Thanks for the post.

[Drew Wiley]

To measure the actual film plane, I took a bar of Starrett precision-ground flat stock,
drilled a hole in the middle, and attached a depth micrometer. My Sinar gear was right
on, as one would expect from a company like this. But my Ebony - which is perhaps the most carefully made wooden camera line - needed a little bit of correction due to
tiny air bubbles caught in the varnish where the filmholder seats. As for plastic "groundglass" of any type, I simply don't believe in it - nearly every type of plastic will bow toward the warm side. Many plastics are also dimensionally affected by humidity. I've personally standardized on Satin Snow groundglass. As for another
culprit, filmholders, for critical work (thinner films or shots intended for big enlargements), I use "precision" filmholders analgous to the Sinar ones. (Won't say how
I make them for personal use or Sinar might get pissed off). But larger films like 8X10
will bow in a holder and this will often noticeably affect the center to edge focus.
I also made my own Quickload/Readyload holder, starting with a 545 carcase, since
the factory-made ones I tested were simply miserable for edge flatness. In large format work it helps to have a few shop skills, or know someone who does!

[Dan Fromm]

[QUOTE=Turner Reich;405657]I took my Shen Hao apart tonight and measured the thickness of the gg and the thickness of the wood that creates the standoff for the format, in this case being 4x5.

The thickness of the ground glass was all over the place, I'm going to put in the Satin Snow that I bought as an extra when I got the camera. <large snip>/QUOTE]

Not to be a complete idiot or anything else horrible, but what does the GG's thickness have to do with anything? I ask because I've been taught that the ground side of the GG faces the lens, not the film, and that the GG is supported on its front. When this is the case, it seems to me that all variations in thickness across the GG/lack of parallelism do is affect, and only slightly, how well focusing aid can be in focus on the image on the front of the GG.

I understand that the GG has to be in register with the film plane, so please don't tell me about that. That has nothing to do with the GG's thickness or parallelism.

What am I missing this time?

Cheers,

Dan

[Drew Wiley]

Film does not automatically set on the same plane as the groundglass, even if they appear parallel. Wood can not only wear but warp. It's quite an art to make a wooden
camera back. You need material known for not only its machinability but its dimensional
stability. The best camera makers use pattern grade mahogany seasoned for at least
twenty years. My Phillips camera uses cherrywood impregnated with epoxy resin. I have no idea of the quality standards of a Shen Hao. With even the best wood cameras, however, I always double check focus not only at center, but at all the edges. If detents are present for zero settings, double check them too.

[Nathan Potter]

Second Dan Fromm, what are we missing here?

Nate Potter, Austin TX.

[Keith Tapscott.]

Ive come from using MF (a Hassy) to 5x4 and I really enjoy LF, BUT something has happened which has totally blown me away....
I just did my first print exchange on APUG, the print that arrived through my front door was shot using a Mamiya 7 and I just cant believe how sharp it is, I mean it really is sharp, sharper than my Hasselblad and dare I say it but it is sharper than my 5x4!

So this got me thinking...Just what am I doing wrong? Is it my technique, my equipment, my darkroom practice?I use modern multi coated lenses and although I have not got years of LF experience I'm pretty happy with using my camera and my darkroom practice is improving all the time.

So is the Mamiya sharper than 5x4? Are the lenses really that good?
Or should I be looking at myself to somehow improve my prints to the sharpness of the Mamiyas?


BTW, I'm not about to go out and get a Mamiya 7, I'm hooked on LF!!


Mike

I have a Mamiya 7 II with only an 80mm lens and it is indeed very sharp, also the Camera`s lightmeter is very good for most outdoor subjects although it doesn`t have TTL metering.
I have two LF Camera`s, an MPP Mk-8 4x5 and a Sinar Norma which allows me to use 4x5 and 8x10 inch film sheets. The Norma has base tilts but not centre tilts, so a bit more fiddly to use when tilts are required, but it still works out fine and is well built.
I was getting some problems with over all sharpness when first using these Camera`s, but it was down to user error on my part.

Keith.

[Neal Shields]

Unless I missed it, I don't think anybody has mentioned flair. Large format lenses put a lot more unused light into the camera. This (unless masked out) reduces contrast. A medium format camera has the lens sized exactly for that format and doesn't need extra image circle. While medium format lenes are usually better than large format lenses in terms of lp/mm the charts I have seen wouldn't explain a percievable difference in the final print, in most cases.

[Nathan Potter]

Since I'm about to leave on a photo trip this discussion got me to thinking about the accuracy of my GG and Quickload and Readyload holders for capturing the plane of best focus. I've not checked this for a while and immediately noticed that the fresnel on the Linhof had become loose on one end - although the GG was pretty much in place. Below are the measurements from the Linhof focusing back and the quick and ready loads that I measured.

Linhof back, 4 corners: .194, .194, .192, .192 inch.
Readyload holder, 4 corners: .193, .192, .188, .189 inch.
Quickload holder, 4 corners: .193, .192, .193, .192 inch.

Measured using a dial vernier caliper from the contact flat to the film pressure plate after cleaning. Some debris had crept into the Readyload between the pressure plate and its forward stop, depressing the plate by about 0.015 inch. Check your pressure plates on these type holders to make sure they are firmly contacted to the backstop on the holder. Spring tension can be inadequate for a variety of other reasons too which means your film surface may not sit as far forward as is needed. This part of LF is really high tech stuff if you want optimum sharpness.

Nate Potter, Austin TX.