Purely Theoretical Musings on Resolutions and Formats...

[sanking]

TMAX is not good for testing resolution because it is too low. TechPan and similar microfilms are much better. But if TMAX can do 100 lp/mm, then the TechPan images look to have 4x the resolution, so at least 200 lp/mm is definately there. I guess I'll give the same comparison link again between TMX vs. TechPan:

http://www.nealcurrie.com/t-comp2.html

I looked at the site above but frankly don't understand the point. How can the comparison be meaningful if the scans were made, as noted in the text of the study, with a cheap scanner? Assuming the cheap scanner was something on the order of an Epson 4990 or higher, maximum true resolution possible is on the order of 2000-2200 ppi, or about 40 lp/mm. I have been able to capture up to about 160 lp/mm on Tmax-100 film when contact printing with high resolution chrome on glass resolution targets. What can I learn about this film from a study that uses a cheap scanner that most likely can not capture much more than 40 lp/mm?

Other point. I am interested in resolution tests but only to the extent that they serve my interests in using films that give good pictorial results. I tried some of the microfilms years ago and while there is no question but they have very high resolution my experience was very negative in terms of obtaining a good tonal scale. Also, my understanding is that the Kodak TechPan film you reference is no longer available, in any format. And, since I don't use 35mm at all, are any microfilm type films available for MF or LF cameras? If not, the film is rather a moot issue for me.

Sandy King

[cotdt]

they were scans from prints so resolution of cheap scanner is not that big of an issue. i'm convinced that microfilms can give much better resolution than fast ISO 100 films, and my rough calculations tell me that TechPan can take full advantage of the available resolution of 8x10 paper.

you can get the full total scale from techpan by using kodak's special developer for it, Technidol. if you look really hard, you can still find 4x5 TechPan film. i saw some on ebay a few months ago. i think they used to make 5x7 and 8x10 TechPan films as well, before I was born.

[Don Hutton]

they were scans from prints so resolution of cheap scanner is not that big of an issue. i'm convinced that microfilms can give much better resolution than fast ISO 100 films, and my rough calculations tell me that TechPan can take full advantage of the available resolution of 8x10 paper.

you can get the full total scale from techpan by using kodak's special developer for it, Technidol. if you look really hard, you can still find 4x5 TechPan film. i saw some on ebay a few months ago. i think they used to make 5x7 and 8x10 TechPan films as well, before I was born.

That's great - they don't make Techpan nor Technidol anymore, so what's the point? You going to spend your life scouring Ebay for single rolls of film which you have no clue as to how they have been stored and are likely to be many years out of date? Why get excited about a film and developer combination which is unobtainable? It's my experience, that making good prints requires far more than fine grained film. In fact I've seen fabulous 16x20 prints made from very grainy 35mm TriX. I've also seen superb 40x50 inch prints made from 4x5 negs with that film you believe cannot produce a decent print - Tmax... Go figure.

[cotdt]

That's great - they don't make Techpan nor Technidol anymore, so what's the point? You going to spend your life scouring Ebay for single rolls of film which you have no clue as to how they have been stored and are likely to be many years out of date? Why get excited about a film and developer combination which is unobtainable?

I have a big secret stash of Kodak TechPan and Technidol in my freezer, including some 4x5 sheets. Besides, there are other microfilms now with similar properties to TechPan.

It's my experience, that making good prints requires far more than fine grained film. In fact I've seen fabulous 16x20 prints made from very grainy 35mm TriX. I've also seen superb 40x50 inch prints made from 4x5 negs with that film you believe cannot produce a decent print - Tmax... Go figure.

That's why this thread is a "purely theoretical" discussion. Of course the lighting and composition of a picture will almost be the most important. But the fact remains that that "16x20 print made from very grainy 35mm TriX" will not be critically sharp, I know because I use TriX a lot, and it does not even come close. For such 16x20 prints from 35mm, TechPan is the only way to the Light.

[Julian Boulter]

I would say that an important consideration to add here is image size and focal length.

I've been comparing Velvia transparencies of similar scenes shot with my Mamiya RZ67 with 110mm lens to my Arca 4x5 with 110 XL Super Symmar, to the eye the transparencies look very similar in quality and if anything the 6x7 just edges it.

Then I thought about it, even though the formats are different, the focal lengths are the same so if I were to take a shot of say a distant landscape with both cameras, the elements of the shot would be the same size on film e.g. trees, mountains etc. The only difference would be that the 4x5 shot would be a wider view of the scene. With the assumption that a larger image size should reproduce better, there should be no gain in quality using the larger format in this situation at any magnification using the same film (aside from quality/resolution of the lenses and the wider view).

However if I were to move in close to a plant and fill the frame using both formats, then the image from the 4x5 will be larger on film and I would then gain all the advantages of using the larger format.

If I were then to use a 210mm on my 4x5 for the distant landscape, the elements of the shot would be roughly twice the size of those shot by the 6x7 with 110mm lens and the field of view would be similar, then I would see an advantage due to the larger image size.

This is all theory by the way so please shoot me down where necessary!

[cotdt]

Julian Boulter, what you say is all true, but here the OP is comparing say a 50mm 6x7 lens versus a 110mm 4x5 lens to get the same picture from the same spot. In addition, to get the same depth of field, the 6x7 lens might be using f/11 while the 4x5 would be using f/22.

[sanking]

they were scans from prints so resolution of cheap scanner is not that big of an issue. i'm convinced that microfilms can give much better resolution than fast ISO 100 films, and my rough calculations tell me that TechPan can take full advantage of the available resolution of 8x10 paper.

you can get the full total scale from techpan by using kodak's special developer for it, Technidol. if you look really hard, you can still find 4x5 TechPan film. i saw some on ebay a few months ago. i think they used to make 5x7 and 8x10 TechPan films as well, before I was born.

I have no doubt but that TechPan has more resolution than a medium speed pictorial film like TMAX-100. However, the resolution of TMAX-100 with my Mamiya 7 lenses ia already so high (80+ lp/mm) that the only way I can pull out all the detail is with a drum scan of at least 4000 spi, maybe 5500 spi. At that point I can make prints 35X44" at 300 dpi or higher, resolution on print well beyond the threshold of human vision.

But in any event, TechPan is no more. So what other films like it are available in MF or LF? Just in case I might want to send some of my negatives off to Lenny Eiger to have scanned on his Azteck Premier at 8000 spi? I am curious about the limits of quality.

Sandy King

[Nathan Potter]

Historically I used to test lens resolution for microchip design using Kodak High Resolution Glass Plates (HRGP). The emulsion was thick and very slow but could achieve about 2000 lp/mm. I also used Kodalith Ortho photo mechanical film when larger format images were required but the development was very critical to control image creep. It may be that there is some current ortho mechanical film still available from other than Kodak that will achieve much better resolution than Tech Pan but I haven't kept up with the market.

I'm inclined to sort of agree with Sandy that it's hard to believe any panchromatic lens say in the 35mm to 6X7 format can achieve better than 150 line pairs per mm. resolution. To do better would require narrowing the bandwidth (using more monochromatic light) so as to reduce the lens sensitivity to chromatic aberration. This is the trick used for the extraordinary current microcircuit lenses mentioned above where reducing the illuminating wavelength proportionately increases the resolution. Additionally using a narrower bandwidth further increases the resolution. Currently monochromatic 190nm eximer laser light sources are in use for extreme resolution although I didn't think that it had reached the 5000 lp/mm. range stated above.

Leonard Evens has mentioned above that the proper method for determining resolution is to examine the aerial image directly with the apparatus mounted on a stabile optical bench and using a focusing telescope to capture the image plane. This eliminates the film variable as well as any vibrational variables and so delivers the intrinsic lens resolving power at the selected aperture and angle of view.

[Jim Jones]

. . . I am interested in resolution tests but only to the extent that they serve my interests in using films that give good pictorial results. . . .Sandy King

Yes, indeed. Lens testing on micro film at optimum apertures in monochromatic light can generate figures appropriate for exaggerated ads, but the results might not grace many galleries or homes. Some of my lenses aren't super sharp or contrasty, but they have produced pleasing images. Also, my old Ford sedan provides reliable, comfortable, and economical transportation, even if it isn't a Ferarri. That's what is important.

[Joerg Krusche]

Hi,

the 110 lp/mm on 6x7 format with a standard 100 film, was that lines per mm or line pairs per mm i.e. if it was line pairs that would mean 220 lines per mm .. sorry for asking this so lately in this discussion.

Joerg