Resolution increases with print size?

[Douglas Broussard]

This might seem like a dumb question, but I'm honestly a bit stymied.

I've been shooting large format for just under three years now, first with a Cro wn Graphic and now with a Wisner Traditional Field. A phenomenon that has consta ntly amazed me is that when printing my large format negatives (TMax 100, typica lly) I percieve an increase in sharpness as print size increases beyond 8X10, up to 16X20 (the largest I've printed so far).

Am I just inventing this perception in my head, or is this a repeatable and m easurable effect similar to the 'better for large prints, not so hot for 8X10s' behavior one sees with digital lightjet/lambda prints from medium and large-form at scans? Is it possible that my diffusion head has something to do with this ef fect? Prints I made last fall with a condensor head on a similar (Beseler 45MX) enlarger and the same lens seem slightly sharper. I normally test with 8X10 prin ts to judge if a negative is worth spending more money (read big paper).

My other theory is that my focussing is less precise with 8X10 from 4X5 because I can't see the darn grain at f22!

-Doug

[fred_1006]

Douglas, lets work backwards for a moment. Are you focusing your negative at the shooting aperture? Wrong move if you are. Focus wide open and then stop down. I HIGHLY recommend the Chromega fine grain focuser (I'm not sure what they call it these days, but it will set you back about $300 and it will be the best money you can spend if you want critically sharp prints). I have used them for years. If you are only taking a 4x5 neg to 8x10 print size or 16x20 print size then you should see no discernable difference either close up or at a normal viewing distance. I have taken 35 mm (kodachrome to 8x10 interneg) up to 14 feet (yup--feet) and it has looked good. This was for Coca-Cola so it had to be right.

I don't understand your Lambda/Lightjet comment at all. There should absolutely be no problems here given a good file size and the percentage enlargement is not huge.

[Bill C]

>> because I can't see the darn grain at f22! <<

Doug, are you actually using f/22 on the enlarging lens for your 8x10s? The diffraction limits work on both sides of the lens; f/22 in this setup would probably just about take the edge off your prints (visually, under critical viewing). If you're really printing at f/22, try getting that aperture open to about f/11 (or wider) and see if that doesn't make a difference.

If this is NOT the situation, someone (I think Alan Gibson) has previously described a good focus verification test: essentially, block your easel up on both sides about 1" and critically focus. Then, switch one of the blocks to the other side; ie, your easel now runs from 0" to 2" height. Make a print; you expect the sharpest point in the middle; if sharpest area is off-center, you have a good idea how much focus error there was.

[mark lindsey]

you guys are thinking too hard.

Doug, yes your prints get sharper because an 8x10 piece of paper doesn't hold a candle to a 4x5 or 8x10 negative, so as you enlarge the image, more information from the negative is spread over a larger surface of paper--allowing more detail to be seen. You can think of it in a digital sense, lets say the paper has 500 dots per inch (dpi), the 8x10 paper and the 16x20 paper may still have the same dpi, but multiplied out, the 16x20 paper has the higher amount of information contained within it.

This is the reason I think the "feel" of an 8x10 contact print effect is baloney, I don't really think anyone can see the difference between an 8x10 printed from a 4x5 neg. or an 8x10 contact print. the paper just doesn't have the resolution necessary to show the difference between the two. and yes, I have shot plenty of 4x5 and 8x10 and printed it, so I'm not just blowing smoke out of my a**.

comments?

[Douglas Broussard]

O.K., just got out of the darkroom, where I tried a couple of things. FYI, my enlarging lens is a 150mm Schneider Componon-S.

<ol> <li>Printed at 16, same neg, same paper (Zone VI Brilliant grade2, my baseline test print paper). It does seem like diffraction may have had something to do with the unsharpness I saw last night. However... <li>I then raised the enlarger head so that the illuminated area was about 16X20 inches in size. I left the 8X10 easel in the same place and printed the negative on an 8X10 swatch, roughly centered. I tested this at 22. </ol>

Lo, and behold: the results seemed much sharper than even the 8X10 at 16. I did it again to make sure.

Personally, I'm inclined to think that this effect directly correlates to enlargement size. I believe the eye has difficulty perceiving the inherent sharpness of the negative at smaller enlargement factors. When the enlargement factor is increased to 16X, the inherent sharpness is much more apparent; there is more paper area for the eye to discern subtle diferences that are lost in a small print.

For what it's worth, the Alan Ross contact print of Ansel's Clearing Winter Storm on my wall is frighteningly sharp, but details like the trees on top of El Capitan would reveal more detail printed at larger sizes, simply because extremely fine detail in the negative, imperceptable at it's native (8X10) size, becomes apparent as it is printed on a larger area.

I still can't see the grain at 16X20. Damn Tmax. ;-)

I may have just re-invented the wheel, but thanks to everyone for the various comments and insight.An explanation of my lightjet comment: over at photo.net, some of the more enlightened regulars have been discussing the relative merits of small digital prints. To whit: Many argue that an 8X10 printed from a 6X7 neg optically would be sharper than a scan and lightjet print of the same negative. Experience seems to bear this out; because of it's relatively low resolution (30x.x dpi in my prints) but extremely high acutance and accuracy the lightjet really starts to shine where optical enlargements begin to dissapoint.

[M.]

How old are you? Do you wear glasses? Perhaps your eyes can't focus close enough to get a sharp 8x10 but you can focus okey at the greater distance to the 16x20?

[Douglas Broussard]

I'm 28, and don't have corrected vision. I make sharp photographs without focussing aids like loupes regularly. I haven't had my vision tested in the past ten years, but I have been known to freak people out by reading eye charts at long distances.

In college and when I first came to California, I partied and drank a lot; that affected my vision, so I cut back quite a bit. I have one-two drinks a week at most now, and I've noticed that my visual acuity and visual purple has improved markedly; I can't recall it being deficient at any time.

[mark lindsey]

Doug,

I have an alps md-5000 that makes amazing prints in both bw and color and they are extremly sharp, it really shows up in small prints up to 8x10 and down to 4x5 or even smaller. You should check it out, they aren't very expensive.

As for the detail sharpness of the 8x10 vs. the 16x20, this is an effect that I have noticed and theorized on for several years. It seems to make sense to me.

[Chris Partti]

Doug,

I have no idea about the resolution issue, but 1-2 drinks per week is not enough. Latest research suggests you should have one a day. Red wine is probably best; I like pinot noir.

[Douglas Broussard]

Hmmmm...back to the vision thing.

I'd never thought of this before...perhaps it was a bit myopic of me (ha ha).

I can 'close focus' my eyes to about two-and-a-half inches in stereo. Luckily for the purposes of this test, I cut myself pretty badly last night and have a gauze bandage on my finger with loose white individual threads perfect for an informal test.

I can pick out an individual thread standing off from the gauze at three inches with stereo vision. With monocular right eye, I can focus at three inches, and monocular left, two and three quarters inches. I'm thinking the differential at least points to the need for an optometrist's opinion.

My tests still suggest that some degree of enlargement beyond 4x might be more peasing to the critical viewer, but I'll get checked up anyway.

To contributors: thanks to everyone for the advice and ideas. Next time you're in Santa Cruz, e-mail me a couple of days ahead of time, and I'll gift you with a tomatoes, basil and and fresh zucchini from my garden!