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Thread: Does anyone know of a 4x5 resolution target?

  1. #11
    Steven Ruttenberg's Avatar
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    Re: Does anyone know of a 4x5 resolution target?

    Quote Originally Posted by Pere Casals View Post
    Steven, you can DIY your own 4x5 resolution target.

    You need a USAF 1951 glass slide, and a sheet of ADOX CMS 20. Then you make several contact copies of the slide in several places of the CMS 20 sheet. The film emulsion side in contact with the printed side of the slide...

    CMS 20 is in fact microfilm material, so it can outresolve anything (until 800 lp/mm). $159 for 50 Sheets, 4x5". You can develop the contact copy with any common developer, as you need no greys.

    What's for the slide you may find cheap ones at ebay (search USAF 1951 glass slide), mine it's good until some 250 lp/mm, it was not reaching what was said, inspected with a microscope, but good enough for what I wanted it, most of the cases you can make an offer, try offering the half, some $40...

    At the end you may need a resolving target sporting under 60 Lp/mm for the scanner, both the cheap slide and the CMS 20 are able for that. And you will also have 49 sheets of CMS to get some fun...
    Cool. Since I have never done a contact image what all do I need to do it properly? Hold glass slide hold glass slide in place, make exposure etc.

  2. #12

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    Re: Does anyone know of a 4x5 resolution target?

    Quote Originally Posted by Steven Ruttenberg View Post
    Cool. Since I have never done a contact image what all do I need to do it properly? Hold glass slide hold glass slide in place, make exposure etc.
    On the enlarger easel I placed a 4mm thick mirror with the reflecting surface down, becasue mirrors are very flat compared with regular window glass, on both sides of the mirror I sprayed some 3M Re Mount glue (only a little, uniformly from far) to keep the things in place.

    on it I placed the film sheet with emulsion side up, on that I placed the glass slide (printed side down) that had attached a black carboard mask. I was holding the glass slide (+ attached mask) in place by pressing steadly with fingers on the slide borders while exposing. Nothing moved...

    IIRC I exposed with 10 Lux during 1s. CMS 20 it's very contrasty if processed with a regular developer (for pictorial usage it requires an special low contrast developer), and this helps to obtain nice bars, well, this comes from the microfilm nature (monodisperse, crystals all of similar size).

    Using a regular contact printing frame can be difficult because the glass slide has a remarkable thickness compared to film and this may end in undesired deformation in the sheet, I not tried it but perhaps it can be used by making a bkack frame for the slide, having same thickness.

    ... and we have to add that we have to do all in darkness, so I used the procedure I described because that. Another choice would be using Rollei Ortho ISO 25 sheets, this allows to work under red safe light, that film is not as sharp/suitable than CMS 20 for that, but still it can be good enough to test flatbed scanners.

  3. #13
    Steven Ruttenberg's Avatar
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    Re: Does anyone know of a 4x5 resolution target?

    Cool. Thanks for the info! Time to get that enlarger. What about sandwhiching between two pieces of glass or like the mirror and a piece of anr glass exposing it to the sun for 1 second? Some how use say a 4x5 film holder put in camera and expose by opening shutter for 1 second without a lens or with it pointing to a white light source?

  4. #14

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    Re: Does anyone know of a 4x5 resolution target?

    Quote Originally Posted by Steven Ruttenberg View Post
    Cool. Thanks for the info! Time to get that enlarger. What about sandwhiching between two pieces of glass or like the mirror and a piece of anr glass exposing it to the sun for 1 second? Some how use say a 4x5 film holder put in camera and expose by opening shutter for 1 second without a lens or with it pointing to a white light source?
    You don't need an enlarger at all, you can do it with a bare tungsten bulb or LED;: https://www.rapidtables.com/calc/lig...alculator.html

    A 20w tungsten bulb throws 10 Lux at 1.5m

    Click image for larger version. 

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    But you also can manage to have the glass slide at the test height on the bed of the scanner, and you save making the target, for you only need some platings of desired thickness separating the slide from the bed.

    but if you want the 4x5 target then you have that way.



    It's good that the illumination source if a bit far (1.5m) because in that way rays come more "parallel", it's also better if the illuminator is small.

  5. #15
    Steven Ruttenberg's Avatar
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    Re: Does anyone know of a 4x5 resolution target?

    Quote Originally Posted by Pere Casals View Post
    You don't need an enlarger at all, you can do it with a bare tungsten bulb or LED;: https://www.rapidtables.com/calc/lig...alculator.html

    A 20w tungsten bulb throws 10 Lux at 1.5m

    Click image for larger version. 

Name:	lx.JPG 
Views:	3 
Size:	26.9 KB 
ID:	182489

    But you also can manage to have the glass slide at the test height on the bed of the scanner, and you save making the target, for you only need some platings of desired thickness separating the slide from the bed.

    but if you want the 4x5 target then you have that way.



    It's good that the illumination source if a bit far (1.5m) because in that way rays come more "parallel", it's also better if the illuminator is small.

    Thanks for the help and suggestions. I think I will make a 4x5 target, but will try the offset of glass target as well.

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