9000 dpi effective DSLR scanner

[Pere Casals]

It is possible to make a 9000 dpi effective DSLR scanner with a Nikkor EL 50mm f/2.8

I was measuring optical performance of an old plain Rodagon 210mm, projecting a USAF 1951 glass slide on the easel with the Durst 138S. I found it resolved Group 7.2 in the projection, it was f/11, in the center, and at x4 enlargement.

This is a crazy deal of resolving power, not bad for lens mostly recovered from trash, $25, with a nice collection of scratches and some balsam separation in the boundaries. This is 143.7 lp/mm on film and 35lp/mm on the paper.

I used a D5100 DSLR to make the measurement, just projecting on the sensor. Y used a D5100 because its back screen can be flipped to focus:







And straight calculation tells that an scanner must resolve 7000 dpi effective to get the same image quality than the DSLR!!!!

[Peter De Smidt]

Um....sure. The trick is not getting that kind of result with a single frame but coming up with a system that'll allow such scans to be used to cover a whole negative. It's been done, by Gigamacro and others. It's not trivial. And my long experience with such systems tells me that it's not necessary for the overwhelming majority of uses.

[Pere Casals]

... then I projected the slide with a Kaiser with the Nikkor EL 50mm f/2.8, 3x, focused at at 2.8 and stopped to 5.6. : 9000 dpi equivalent !!!


So here comes the idea:

> A motorized neg carrier displaces the negative to take the crops

> DSLR is at the bottom without the lens, perhaps with an UV filter on the mount to not take dust.


Everybody can test this at home...


I was not understanding how that old gear could deliver such amount of IQ on the prints... what I was seeing on the prints with the magnifier amazed me...

[Pere Casals]

it's not necessary for the overwhelming majority of uses.

Well, my view is that for 35mm one may get 9000 effective dpi by stitching 16 crops (4x4). This may be useful to scan ADOX CMS 20 shots made with extraordinary lenses. It also may be useful to catch perfectly the BW grain structure and enlarging a lot.

For LF it would deliver top drum like performace, and way faster.

[Peter De Smidt]

Some people on this site have even built and tested such systems... But you just like to argue, and so I'm checking out.

[Pere Casals]

Peter by far I'm not saying I'm the first who discovered that, I'm only sharing what I personally measured, and explianing the way I measured it, also it can be interesting for someone wanting to rate his enlarger lenses or to learn the sweet aperture/magnification: using a DLSR with a tilting screen.

[calebarchie]

Dear dear, the irony. I have witnessed many of the DSLR scanning folk essentially trying to design a film scanner backwards, completely forgetting the sole 'benefit' of DSLR scanning they once clinged to. All I'll say is search, and you shall find.

I could say much more, worse and better things but I'll refrain - not worth the energy from what I've seen and experienced in the past.

[calebarchie]

BTW - I think you are doing your calculations wrong, I am not seeing 7000 DPI effective from what you are posting but my brain is fuzzy.

[Pere Casals]

BTW - I think you are doing your calculations wrong, I am not seeing 7000 DPI effective from what you are posting but my brain is fuzzy.

The calculations are right, Group 7 element 2 is 143.7 lp/mm, multiply by 25.4 and by 2 and you have 7299,96 effective dpi, following criterion in ScannerInfo web site. About your brain, I can't tell.

I have witnessed many of the DSLR scanning folk essentially trying to design

It took 11 Apollos to reach the moon.

[calebarchie]

Sorry, I can't see group 7 from your picture?

And one would assume NASA did a lot of research before hand, unless the US government just likes wasting money.

I just noticed the extra added personal comments after the fact, I am definitely out.