Meaningful resolution - from my old website

I needed to re-enter this information as I got wrapped around the axle and lost the first post of this just a moment ago.  Flying fingers and all that -

How to calculate visible resolution limits

Bob Wheeler implied that there should be some minimal requirements for enlargements being made from LF and MF equipment (at least this is what I think he was implying). We can calculate these requirements as follows:

{line/mm eye resolves} x {neg/trans enlargement factor} = {minimum l/mm required to fully resolve what the eye can perceive on final print}

This will give a good starting reference for establishing the minimal system resolution requirements. Indirectly, one can use this to determine if their photo system is capable of delivering the desired resolution.

If we assume full frame enlargements (no cropping), a tripod is used in all cases (to eliminate shake from the system), a 'good' enlarging system (no loss of resolution from neg/trans to print), and the fact 'young' human eyes are reported to be able to resolve 7 lines/mm, the following can be assumed:

For 4x5 negatives and transparencies:

• 8x10 inch prints require a system to resolve 14 lines/mm
• 16x20 inch prints require a system to resolve 28 lines/mm

For 6x6 negatives and transparencies:

• 8x10 inch prints require a system to resolve 28 lines/mm
• 16x20 inch prints require a system to resolve 61 lines/mm

For 6x7 negatives and transparencies:

• 8x10 inch prints require a system to resolve 25 lines/mm
• 16x20 inch prints require a system to resolve 51 lines/mm

Several things become immediately apparent:

1. To make a 16x20 print from 6x6 requires all the resolution that many of the MF systems Mike, Kerry, and I tested can deliver.

2. It would take a really poor LF lens to resolve the 28 l/mm required to enlarge from 4x5

3. If one works in 6x7 the requirements are less stringent than 6x6 to reach 16x20, but a system must still be 'pretty good'.

4. When reviewing our tests on folding cameras (specifically the Balda and Kodak Special Six20) one can see there is adequate resolution for most tasks. _For me_ this means portability of photo equipment when working in field need not become a consideration as long as I don't mind using just one lens (ala Henry Cartier-Bresson :-).

5. Almost any camera can resolve the numbers required to print a great looking 8x10... :-)

I hope this helps...
- Chris