Resolution of slides

[Carolreid]

Hi,

I am scanning dozens of slides for a slide show which will be shown on a digital projector - NOT just a monitor screen.

For PTE to show I need the scanner to scan for 13" X 8.5" at 72 ppi with 962x630px giving 1.73Mb file for each image.

It difficult to check the projector settings (house isn't long enough) but will theis 962X630 px be enough?

Using the Nikon CoolScan I can change the 13X8.3" OR 72ppi OR 960X630px.

The size of the final file doesn't really matter since it will be saved to CD and is not for WWW use.

What to do?

HELP!!!! I'm getting one of my headaches.......

Carol

[Guest guru]

Hello Carol!

I don't know which model of Nikon CoolScan you use, but sure it is able to scan at much more than 72 ppi, and allows to get pictures (from 35mm slides) much larger than 962 x 630 pixels. See the instruction manual of the scanner.

This size (962 x 630) can be enough to create a presentation optimized for a 800 x 600 resolution, but not if you want to have a very high quality. Most digital projectors can now reach 1024 x 760 pixels, and with this setting (you must set it from your computer) the pictures won't fill the screen.

I hope I've been clear enough... If not, please write us again!

[LumenLux]

The size of the final file doesn't really matter since it will be saved to CD and is not for WWW use.

What to do?

HELP!!!! I'm getting one of my headaches.......

Carol

First of all, skip the headache.

Secondly, follow Guido (guru) direction.

Third, consider that file size might well matter, even though on CD. PTE slides of 1+ megabites each may tax your computer processor and trouble your show. After you get the scans you want, you will likely want to compress to maybe 50 or 60 level .jpg and see where that leaves you quality vs. file size. Many users get very good quality while keeping file size less than 200k per slide.

Fourth, don't go back to the headache.

[Ed Overstreet]

In my experience (I use a Nikon Coolscan IV/LS40) you should always scan your slides at the maximum resolution of which the scanner is capable, in my case at 12 bits and 2900 ppi which gives a scan of about 3900 by 2600 pixels, depending on your slide mounts. Scan directly into Photoshop through the TWAIN interface and edit the slide as you would any other slide scan. When you've finished editing the slide, then resize the image to fit a canvas no larger than 1024 by 768 pixels (use Photoshop Image Size with bicubic interpolation); the exact dimensions of your scan will depend on the cropping you've done, if any. Save to a JPG (you'll need to have converted the image to 8 bits by now in order to do this) at a Level 5 compression in the Save As JPG dialogue box; this will give you a file of maybe 100 kb which any system should be able to handle in PTE without difficulty.

Always scan at maximum resolution and edit the image at full size, then resize when the edits are finished. This gives you vastly better-looking images (and the 12-bit scan depth gives you much better shadow detail) than you'll ever get scanning at lower resolution and then trying to work with the image.

The "inches" dimensions in Image Size in Photoshop are totally irrelevant for monitor/projection/PTE display, they're only important for printing. Ditto the dpi/ppi display. All that matters for PTE, web, monitor, or digital projection is the pixel dimensions of the file. As already noted by others, most digital projectors can handle 1024x768 screen size and hence image sizes in PTE. In our experience (in the photo club of which I am a member in Ottawa) digital projection looks best at 1024x768 screen resolution, regardless of the image size. PTE can usually display most images JPG'd as noted above very smoothly at that screen resolution, though some members prefer to resize their images to 800x600 pixels and display at 1024x768, but I've never seen the point to this, as you're not making full use of the "screen real estate."

BTW if you are mixing images in both portrait and landscape orientation, you might want to consider fitting all your images within a 768x768 pixel canvas, so the verticals and the horizontals appear to have the same size and area, which they won't if your horizontals are 1024x768 but your vertical images will therefore have to be 576x768 pixels.

Hope this helps; if you have any further questions on the points I raise, feel free to email me.

[Carolreid]

Hi Ed,

>In my experience (I use a Nikon Coolscan IV/LS40) you should always scan your slides at the maximum resolution of which the scanner is capable, in my case at 12 bits and 2900 ppi which gives a scan of about 3900 by 2600 pixels, depending on your slide mounts.

If I were printing out the slides then I would want to scan to the highest resolution. Since I am not printing them out I thought that I could "get away" with a lower resolution(and therefore a faster scan time)

Using 12 bits instead of 8 almost doubles the scan time!

>Scan directly into Photoshop through the TWAIN interface and edit the slide as you would any other slide scan. When you've finished editing the slide, then resize the image to fit a canvas no larger than 1024 by 768 pixels (use Photoshop Image Size with bicubic interpolation); the exact dimensions of your scan will depend on the cropping you've done, if any.

I find it easier to do all the scanning first and then the Photoshopping later.

However, this method of yours means that HUGE files would be lying around waiting to be compressed.

>Save to a JPG (you'll need to have converted the image to 8 bits by now in order to do this) at a Level 5 compression in the Save As JPG dialogue box; this will give you a file of maybe 100 kb which any system should be able to handle in PTE without difficulty.

Obviously you think it is worth the extra effort in order to get good images on screen.

>Always scan at maximum resolution and edit the image at full size, then resize when the edits are finished. This gives you vastly better-looking images (and the 12-bit scan depth gives you much better shadow detail) than you'll ever get scanning at lower resolution and then trying to work with the image.

>The "inches" dimensions in Image Size in Photoshop are totally irrelevant for monitor/projection/PTE display, they're only important for printing. Ditto the dpi/ppi display. All that matters for PTE, web, monitor, or digital projection is the pixel dimensions of the file. As already noted by others, most digital projectors can handle 1024x768 screen size and hence image sizes in PTE. In our experience (in the photo club of which I am a member in Ottawa) digital projection looks best at 1024x768 screen resolution, regardless of the image size. PTE can usually display most images JPG'd as noted above very smoothly at that screen resolution, though some members prefer to resize their images to 800x600 pixels and display at 1024x768, but I've never seen the point to this, as you're not making full use of the "screen real estate."

This also means, I suppose, that the "fit to screen" function in PTE is likely to

reduce the quality of the image even further if it has not been scanned to max to start with.

>BTW if you are mixing images in both portrait and landscape orientation, you might want to consider fitting all your images within a 768x768 pixel canvas, so the verticals and the horizontals appear to have the same size and area, which they won't if your horizontals are 1024x768 but your vertical images will therefore have to be 576x768 pixels.

That is a good tip!

I think its back to the drawing board for me!

Thanks again,

Carol

[Bert]

My question concerns cropped images. I have scanned a vertical slide at 3264 pixels wide x 2520 pixels high. I want only to use one half of the slide and after cropping end up with a vertical image of 1470 pixels wide x 2062 pixels high.

If I wanted to make a print of this image at say 8 x 12, I would resize it up 160% (bicubic resampling), to get a vertical with enough pixels to print.

How does this work for a slide show? Do I resize the cropped image 1470 x 2062 to a 549 x 768 jpeg to fit on the screen, or do I resize it up first 160 % and than resize it to a 549 x 768 jpeg.

Thanks,

Bert

[Guest guru]

A good question, Bert!

If you resample your picture at 160%, you create "interpolated" pixels, which don't add anything to image's detail.

Actually, you must discard several pixels to get a 549 x 768 picture for your presentation: so it doesn't make sense to increase pixels (artificially) before the resampling.

A little addition: if you want to enhance your picture (colours, sharpness etc.) for PTE, save the 549 x 768 slide as Tiff or Bmp, and save it as Jpg only the finished image.

[potwnc]

BTW if you are mixing images in both portrait and landscape orientation, you might want to consider fitting all your images within a 768x768 pixel canvas, so the verticals and the horizontals appear to have the same size and area, which they won't if your horizontals are 1024x768 but your vertical images will therefore have to be 576x768 pixels.

I use 800x600 for screen/lcd projector shows. All my shows mix portrait and landscape and I find the

following to look OK when I go between the 2:

E.g., 800x600 landscape -> 450x600 portrait. Make a second copy of the 800x600 image and "mask" it

on each side so that it is the same image but with the center 450x600 pixels showing. This second image

is still 800x600 pixels, but the viewable part of the image that shows is now 450x600 pixels portrait. Do

a fast (no effect) transition to this second slide and show it for a small (e.g., 200 msec) amount of time

before transitioning to the third, 450x600 portrait image.

I've found that if you don't do too many of these in a show it works quite well.

Ray

[Ed Overstreet]

Hi Ray. Neat trick, similar to something we used to call a "fade to black" effect with a two-projector dissolve unit, wherein you start to fade the first image to a black screen then begin the transition to the second image while the first fade to black is still in progress, about half-way. We generally did this when going between landscape and portrait orientation, but I also used the same effect sometimes within the same orientation but where the fade would otherwise be a bit messy-looking. That trick can't be done in most av software though there's an effect in the newer versions of Internet Explorer DHTML code that permits this. However you could I suppose simulate it with a genuine third image, a separate file inserted between the two where the insert is the first image overlaid at 50% opacity on a black canvas ...

The trick you describe is a variation on another two-projector trick some of us used, where we'd insert between a landscape and a portrait image a third image (in your case it would be a duplicate of the first image) mounted in a Gepe plastic clear mount in which the two halves of the mount were rotated at 90 degrees instead of correctly aligned, giving a square aperture instead of a 3:2 aperture, as an intermediate transition between landscape and portrait orientations. Your trick in PTE is more flexible, however, since it can be adapted to any aspect ratio other than 1:1 or 3:2.

Another trick for going between landscape and portrait orienation is to use an appropriate horizontal/vertical gate effect.

We used to have lengthy debates in the old two-slide-projector days about the landscape-to-portrait transition issue; there are times where doing a simple fade can work (depending on the subject matter in the images) and times where you really want to avoid the "cross-over" third image that appears during a simple fade. Others took the approach of sticking to one orientation or the other throughout the entire show, which sometimes makes sense with some subject matter (e.g. landscape-only orientation during shows based on actual landscapes and portrait-only orientation for shows based on portrait/studio photographs of people) though it can be a bit limiting having images only in one orientation.

Sorry this posting and yours are a bit off-thread here, maybe if others are interested we could have a separate thread on how to deal with varying image orientations in a show. I've already touched on this in one of my The Third Image thread postings, since the the landscape-to-portrait issue is a special case of the more general issue in which images in a sequence don't all have the same aspect ratio, which in turn is a special case of a "third image" on the screen where the "third image" (the overlapping image that appears during the transition between two images) displays partial-opacity areas that the two images don't have in common.

None of these issues are relevant when you opt instead for running a show with images sized less than the full screen (e.g., 800x600 or even 600x400 images placed on a 1024x768 canvas) and don't centre the images but move them around the canvas, which can be interesting and opens up possibilities of multiple non-overlapping or partially-overlapping images on the screen simultaneously, something you couldn't do with two slide projectors though with lots of patience and money you could achieve with three or more slide projectors. But I digress, sorry