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Measuring film resolution

Rudeofus

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Joined
Aug 13, 2009
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Medium Format
I have seen many characteristic curves for film&developer combos posted here, but for full evaluation of film&developer we also need to look at resolution. For this purpose I would contact print resolution targets onto my film and then try to extract the relevant data from developed test clips.

Looking for suitable contact printing masks gave me two categories of product: simple gel targets like the one offered by Stouffer, which don't cover the range of resolutions achieved by modern film, and very expensive very high resolution glass targets like the ones made by Edmund Scientific, Thorlabs and others.

Is there something in between, which covers resolutions up to 100-150 lp/mm while costing less than US$100? How do others here measure film resolution? Are there affordable targets for measuring MTF from 20-100 cycles/mm? Is there a dedicated used market for such things?
 
I am not expert but They report latest zeiss lenses have 450 and Older Leitz lenses have 250 lpmm resolution. I dont have knowledge whether film can record that but some holography emulsions records 5000 lpmm. I cant think that measuring film up to 100 lpmm covers lens resolution. If you cant measure what lens can do on film , I guess 100 dollars goes to nowhere.

Umut
 
Umut, I am not after lens resolution, and most films do substantially less than 200 lp/mm, especially the higher speed ones. Also note that few to none here will get 100 lp/mm under normal shooting conditions regardless of lens or film used.
 
If you are sufficent with relative resolution (for film comparison) than photographing a resolution target would be the cheapest way to go
 
Why are you wanting to do this? Personally I find it easier to read what the film datasheet tells me and if it isn't there I'm sure a letter to the manufacturer would give you the answer.
But what use would knowing the answer be anyway?

If you don't have the equipemnt and the ability to setup a truly accurate scientific test the result won't be accurate and that means taking the manufacturers word for it is good enough.
 

A fair point but the resolution of a film is dependent upon the developer eg an edge developer will improve contrast so the film will appear to resolve better.

So any datasheet resolution should indicate developer...

Since we have so few films left if you had decided you liked plusx or neopan 400 it would not be nice.

And we have lost the best two IR films...

Acros is likely to be high resolution and ...

The simplest way to compare two films if that would do is with your best lens a lens testing chart and a microscope.

But clearly the lens will degrade both resolutions.
 

I looked up for the test charts and they are very expensive , starts from 200 dollars to go to 900.

May be digital negative , professional prepress house film output could be used. There are too many dot printing , grouping technology outthere and they cost 1/10 of the cheapest chart. At 1994 , I printed my drum scans with 170 lp/mm , now may be they can printed 3 times more or more.

There are even blue laser printer test charts used by operator to calibrate the laser power and developer roll speed.

But this was 20 years ago and I dont have idea how things done today , we were using 60mhz mac that day. 1/100 of today , internet speed was 15 kbps. You can design a test chart at photoshop if you can.

Umut
 


This is why, in the final analysis, one does a system sharpness or resolution measurement. Even the surface of the paper will degrade resolution.

And, an edge developer does not need to increase contrast. In fact it can decrease it under certain circumstances. But, OTOH, doe you want edges that improve micro or macro contrast? In the case of 35mm to 120 to 4x5 one could posit a change in macro vs micro contrast to optimize each size for the proper edge effects. Of course this is chancy, but can be done.

PE
 
I'm not going to worry about it too much... certainly not enough to go through painstaking tests. I can glean what I need from the internet and if I'm not liking what I see in my own work then I'll change my equipment, materials or procedures as needed.
 
There's one on eBay for US $99 with free shipping that looks like it goes above 228 line pairs per millimeter.

That's less than $100.
 
Rudeofus said:
How do others here measure film resolution?
Click to expand...

Film resolution is difficult to measure. If you acquire a proper test target you will be one of the few to post results here. Most threads on the topic of film resolution contain too much nonsense to reveal anything useful.
Since you will be doing all the readings yourself by eye (without a microdensitometer) you could come to reasonable conclusions. Realize that even if you do find an affordable target, different styles give different results (Mericsko & Collier, 1970).
 
I have 4 test targets.

One pair is 4x5 and is used for contact printing tests that apply to the whole system.

Another is 35mm and is evaporated metal on glass for enlargements or contacts.

These are pos-neg pairs of the same image. To do resolution you need to do both and measure the change induced by the two types of image.

In addition, I have about 4 targets to use when taking photos so as to test the system from start to finish. The other images are used to test from exposure to print. Examples of the latter are given in my book. I rarely find it useful to do the whole battery of tests.

PE
 
Very easy to make your own target.

I've done film+developer combinations before, one of the things I found is I could not exceed 55 lp/mm with FP4+ and Xtol or Rodinal 1+25, or 40 lp/mm with 1+100 stand with FP4+, modification of the developer got it up to 90+ lp/mm.
 
I have never really understood the resolution/sharpness battle.
What difference does it make if there is a 100+ lp/mm kind of set?
Unless I would archive a painting or antique print or a kind, I do not know why would resolution matter.
Regards
 
sagai said:
I have never really understood the resolution/sharpness battle.
Click to expand...
Resolution translates directly into enlargeability, assuming the rest of your equipment is up to snuff, and you will see my point quickly if you ever try to enlarge a 35mm Delta 3200 negative to 30x40cm. A decent resolution target can show you the limitations and possible imbalances in your film/developer combo: mushy images lose image detail regardless of fine grain, and overly grainy image structure loses you resolution even if image is perfectly sharp. Note that you can't have both high sharpness and fine grain at the same time unless you compromise film speed. Sometimes you want to tilt the balance in one direction or the other, depending on what you want to show.

Since all film developers are sold as "fine grain, good sharpness, gives full box speed", you're on your own if you want to know what's going on. Athiril's claim that he upped resolution from 40 lp/mm to 90 lp/mm tells me that there is potential.
 
Thanks, it does make sense in essence.
I only would doubt if a 30x40cm print is a possible print size anyway for that very high speed 35mm film.
But of course I got it, thanks!
 
Athiril said:
Very easy to make your own target.
Click to expand...

Adox CMS 20 film claims upto 800 lp/mm. Please tell us how its so easy to make a target for this film using contact printing as OP says he wants to do the test.

Note that Zeiss say they have obtained 400 lp/mm on film using this film(Spur variant) with a production camera lens so these aren't fictional values.
 

my question is:Why does it matter and isn't sharpness more important than resolution?
 

They follow ISO 6328, use in-house developed tools, a few Siemens stars variations, for resolution, colors, mono, lens elements centering, etc.
 
RalphLambrecht said:
my question is:Why does it matter and isn't sharpness more important than resolution?
Click to expand...

I always thought sharpness was a function of CoC size and nothing to do with developer. But hey ho there seems to be a school of thought that you focus with your developer.
 
RalphLambrecht said:
my question is:Why does it matter and isn't sharpness more important than resolution?
Click to expand...

A contact printed resolution target tells you both limit resolution and which image property dominates that limit. It is entirely up to you whether you favour sharpness over grain, but you'd rather make an informed decision than rely on anecdotal evidence or marketing drivel.

RobC said:
Adox CMS 20 film claims upto 800 lp/mm. Please tell us how its so easy to make a target for this film using contact printing as OP says he wants to do the test.
Click to expand...

Realistic shooting conditions won't give you more than 100 lp/mm. To give you an impression:
  • For 100 lp/mm your CoC can't be larger than 2-3 µm, which means you have about 1/10 of DoF which you would normally have, e.g. a 50mm lens at F/2.8 and 3m subject distance would have 4cm of total DoF). Good luck getting focus sufficiently accurate, and subject matter with less depth.
  • Because of diffraction limits, you have to shoot at F/2.8 or larger aperture if you want 100 lp/mm. Few medium format lenses open up to F/2.8, and even fewer large format lenses. Very few small format lenses reach 100 lp/mm at F/2.8 or larger.
Extend this argument to resolutions beyond 100 lp/mm and see what you get. 200 lp/mm would require you to shoot at F/1.4 and give you 1 centimeter of DoF in the example above.

Now if we look at the Zeiss document where they claim 400 lp/mm at F/4: we can safely assume that these 400 lp/mm come at a significant loss of contrast, which is ok with test charts, but not ok with real world image matter.

RobC said:
I always thought sharpness was a function of CoC size and nothing to do with developer. But hey ho there seems to be a school of thought that you focus with your developer.
Click to expand...

There are some tricks to increase perceived sharpness of an image, and several popular developer formulas put these to use. These tricks don't increase real resolution, but fake the impression of a very sharp image, just like unsharp masking. Like the latter, these developers usually create stronger granularity. And that's where Adox CMS 20 film becomes useful: even if you boost its grain a great deal, it's still finer grained than what your lens can handle, and together with a sharpness enhancing developer you can create very fine grained and very sharp looking images, albeit at ISO 20.
 
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I 'basically' understand diffraction limits and often traded single-plane sharpness for DoF. However, when I traded off DoF for single-plane sharpness I wanted that plane damn sharp. The latter condition and with mural-sized prints is primarily where overall final print resolution is most important, IMO. And I am a grain peeper. I like to walk up with my nose to very large prints and feel like I'm 'there'.
 
Rudeofus said:
Realistic shooting conditions won't give you more than 100 lp/mm.
Click to expand...

This is the crux of it and what I have been maintaining in my arguments through all the arguments about this. You MUST set out with the intention of achieving technical perfection and this means excellent lenses, excellent technique etc etc. If you don't do that and settle for mediocrity then you can't expect to be able to make very large prints from small format film and get anything anywhere near approaching what mediocrity in LF can achieve.
Problem is that most don't even know what and how to achieve it and further more they don't own the necessary lenses/equipment either. Of course that means their experience will say its not possible.

The apparent sharpness obtained by developers is 100% the wrong term. It is "acutance" which decreases the development around the edges of grain clumps due the bromide production which inhibits development. Humans percieve that as increased sharpness but it is isn't and in fact is usually reduced resolution as its putting into an image what was not there in the first place. On the highest resolving films that means less than 1/400 mm for the edge effect to occupy before it reduces resolution. The edge effect producing developers ( e.g. rodinal ) will usually use much more space than that, so much so that you can see it in the neg with a low power loupe.
 
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