Railfan Technology > Scanning Slides for Projection

If I want to make scans of 35mm slides to be used for projection in a meeting, what size should I make the scans?  For example, Train Orders sets the maximum width at 1000 pixels.  Is that appropriate for projection, or should they be larger?

Thanks,
Marty Bernard

Depends on the projector's native resolution.

Scanning is the slow part so plan on doing that once then don't have to do it again. Scan at the highest resolution which looks good then make that an an archival file. Then if you want a print or projection image then make a copy of the archival file and reduce the copy to the size and resolution you need.

Posted from iPhone

I meant my question to be generic.  I don't have a partiular projector in mind.  I also want to think into the future.  While I'm scanning at high resolution I am wondering about a good working size that will both project and be workable for Internet forums.  By working size I mean the one I put ythe effort into to clean up and post to places like Train Orders.

Marty



Edited 1 time(s). Last edit at 09/18/15 21:51 by MartyBernard.

fbe Wrote:
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> Scanning is the slow part so plan on doing that
> once then don't have to do it again. Scan at the
> highest resolution which looks good then make that
> an an archival file. Then if you want a print or
> projection image then make a copy of the archival
> file and reduce the copy to the size and
> resolution you need.
>
> Posted from iPhone

I scan at high resolution and never touch that file except to copy from it.  The first copy I make right away and clean it up so it is a good photograph.  That is what takes the time.  My question is what size should that image be to be able to project it.  1000 pixels wide?  2000 pixels wide?  What?

Marty Bernard

My projector resolution is 1024x768 so that is the size at 76 pixels I use for images I project.

Some show managers will set the longest dimension of the image at 768 pixels so landscape images are 768x512 and portrate images are 512x768. That way vertical images do not seem small compared to horizontal images on the screen.

There is a projector resolution which is somewhere around 1200 pixels wide and an older one in the 760 pixels wide range.

Commonly, the display software will reset the image to match the screen resolution of the projector but that may slow down the show if the differences are too large.

Hope that helps.

Posted from iPhone

If you want to produce an archival scan so that it's one and done, then you want to scan at a resolution that captures every detail that film can.  Although film isn't strictly pixels, it does have a minimum feature size driven by the grain size, etc.  For good slide film, it's roughly 4000-6000 pixels per inch of usable resolution.  Basically, the film has more resolution than any consumer-grade scanner can resolve.  To extract it all, you need either high end film scanners or more exotic tech like drum scanners.

My advice is scan at the highest optical (aka real) resolution your scanner supports.  Some scanner drivers offer higher resolutions that exceed what they're optically capable of, so check the spec sheet. 

Without a specific projector in mind, I'd probably leave your pictures at highest resolution and let the computer and projector 'figure it out'.

What it comes down to is the quality of the video card to which the projector is connected.  In my opinion, the image quality capabilities of the video card is what controls handling images at higher or lower resolution that what is currently being displayed.  Whether it's the video driver software or the card itself, the interpolation/extraction of data is not in your hands.  I suspect that setting the display resolution in the computer one way or the other would have a noticable effect on what comes out...no different than changing it on your computer at home. 

And, for what it's worth, the projector at the church I belong to 'washes out' everything!  So I intentionally over-saturate the colors a bit when I have to.

MartyBernard Wrote:
-------------------------------------------------------
> If I want to make scans of 35mm slides to be used
> for projection in a meeting, what size should I
> make the scans?  For example, Train Orders sets
> the maximum width at 1000 pixels.  Is that
> appropriate for projection, or should they be
> larger?
>
> Thanks,
> Marty Bernard


As others have suggested, scan at the highest resolution that your scanner will scan.

I have a Minolta 5400 and scan slides at 5400 dpi and save as 4000 dpi TIFF files..  They come out about 100+MB files
! then resize to 3000 x 2250 pixel images and save as a JPEG.  Use this image in your slide show.
I use ProShow Gold for my programs.  You can customize the output for the projector you are using.

I have presented twice at Winterail in the last 5 years and this is the formula I use.

Here is a scan that has been resized from 4000 x 3000 scan TIFF to 792 x 509 JPEG
UP Special SB at South jct, OR on Oregon Trunk in mid 90's

Nomosantafe
Portland, Oregon
“Pacific Wonderland”



Edited 1 time(s). Last edit at 09/19/15 21:53 by nomosantafe.

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MartyBernard Wrote:
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> If I want to make scans of 35mm slides to be used
> for projection in a meeting,

How about just projecting the slides?

"How about just projecting the slides?"

Digitization of the slides can be used to correct color balance and exposures of the slides making a better presentation. Some venues are going digital only.

Posted from iPhone

That's my philosophy when showing slides in my basement or at venues that have small meeting rooms.  The slide projector can easily handle the light output needed to ensure the slides on the screen are nice and bright.  In my opinion, in that scenario original slides are far superior to scans of slides shown with a digital projector.  However, if you're showing in an large auditorium like Summerail and Winterail then digital projection is pretty much a must.  Even with the highest quality projectors and projector lenses the images are going to look dark on the screen when projected for that kind of distance.

Incidentally I use Kodak Ektagraphic IIIA projectors with the Kodak Extra Bright lamp modules and usually a Navitar 70-125mm f2.8 lens for my slide shows dones outside my home.  At home I use 4" Kodak Ektanar f2.8 lenses.  I have not yet bought a digital projector, but need to, so the information that has been posted here is quite informative.

sig292 Wrote:
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> How about just projecting the slides?

Currently with projectors getting better I would use 1500 pixels. Or just use a jpg version of your hi res original tiff and when done with the show most progams have a "reduce file size" option in a menu. Select that to optimize the size of the show program.

Rich

MartyBernard Wrote:
-------------------------------------------------------
> If I want to make scans of 35mm slides to be used
> for projection in a meeting, what size should I
> make the scans?  For example, Train Orders sets
> the maximum width at 1000 pixels.  Is that
> appropriate for projection, or should they be
> larger?
>
> Thanks,
> Marty Bernard

Marty,

In the early days of digital presentations, most projectors output was 800 pixels wide. Then came along 1024 wide. Then 1200, etc. Now I think projectors at some venues project up to 1900 pixels wide, or a little more. So the question is answered by scanning slides at the highest possible resolution and save as TIFFs. Then, convert the tiff to a jpeg and a size like 1024 x 683 or 1280 wide. Then, if you end up knowing a show you are producing has a projector that outputs at the high end, like 1900 wide or more, your pictures sized at 1024x683 (for example) will only fill a part of the black "canvas", what area is "projectable", if you will. So that means you have potential to create a canvas with two, three, or four smaller pictures in one view.

Bottom line, projectors and computer screen resolution continues to increase.

Best wishes with that great collection of yours.

chico