Should I use high resolution stills in Keynote?

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Level 1

112 points

Should I use high resolution stills in Keynote?

Preparing a Keynote presentation requiring lots of stills/movies -- this is to be streamed from an international conference worldwide. So I don't want to mess up.

I have high resolution stills (the originals were RAW, I converted them to PNG's). Do I want to build my Keynote with the high resolution PNG's, or do I want to batch convert them over to JPEG's before inserting them in the Keynote? What would be an optimum file size per pic. There will probably be about 100 or so stills, plus a dozen short movies (it's an hour and a half presentation I believe).

Or, if I do use high resolution PNG's (15-20 megs each), is there a function in Keynote that reduces the file sizes?

And, if so, am I better to batch convert the PNG's to JPEG's, or just use the PNG's and let Keynote do the optimization?

For the movies I'm going to convert everything to H264 (same resolution as the Keynote presentation - 1920x1080 - using the same optimum bitrate as one would use for Vimeo).

All ears,

Ben

MacBook Pro (15-inch Glossy), Mac OS X (10.6.8)

Posted on Jun 9, 2016 3:11 PM

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Answer 1

Jun 10, 2016 2:49 AM in response to Ben Low

Size the images to match the slide size in Keynote; in this case they should be 1920 x 1080 pixels

as they are PNG files keep them as that

Batch convert the images as follows:

Open the whole batch of images in Preview

Select all of the thumbnails in the sidebar - click on one image in the side bar then (Command-A)

from the Tools menu, choose Adjust Size

use custom size and enter 1929 x 1080

Save

Place the images in Keynote as follows; drag all the images into the Navigator (the side bar on the left) and a new slide will be created for each image, centered and scaled full screen

If the images are larger than slide size, they won't look any better, they just take up more space

if the images are smaller than slide size, they will reduce in quality

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Answer 2

Ben Low Author

Level 1

112 points

Jun 10, 2016 6:41 AM in response to Gary Scotland

Thank you most kindly Gary. This is very helpful. I'm going to try it out immediately.

You suggest that Keynote 'creates' a new slide for each image I've imported in ... meaning Keynote determines the best resolution for Keynote when it makes this new 'slide'? Meaning, I don't have to concern myself if the original image is a 20 meg .png or a 2 meg JPEG? I want to get the best quality possible displaying out of the Keynote, but not create any issues with file sizes embedded in the Keynote. The actual size of the final Keynote master file is not that important (to me), it's more about smoothness of operation, playability.

Ben

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Answer 3

Jun 10, 2016 8:12 AM in response to Ben Low

meaning Keynote determines the best resolution for Keynote when it makes this new 'slide'?

No, Keynote creates all new slides using the values in: Inspector > Document > Document > Slide Size.

If the slide size is 800 x 600 all slides in that presentation will be 800 x 600 no matter what images are placed on the slide.

You determine the best resolution for the project based on how the end product will be used, you need a high pixel count for images destined to be shown on a 4K video wall, its more efficient to use a much lower count for a 19" desktop display.

I have clients who have projectors with a resolution of 1920 x 1200 pixels, so thats the resolution of the Keynote slide size I give them, I then downsize all graphics to 1920 x 1200 pixels to match the slide size.

I don't have to concern myself if the original image is a 20 meg .png or a 2 meg JPEG?

Yes I agree, what determines image quality in Keynote is the amount of pixels in each image, not how many mega bytes the file is.

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Answer 4

Ben Low Author

Level 1

112 points

Jun 10, 2016 9:04 AM in response to Gary Scotland

Thank you Gary. Most helpful. And reassuring. It's going to be a long week, and knowing this one fact will take a load of stress out of the equation.

All the best,

Ben

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Answer 5

Ben Low Author

Level 1

112 points

Jun 10, 2016 9:16 AM in response to Gary Scotland

S

Aha! One other thought. I'm going to pull in 1920 x 1080 stills. The Keynote project has to be that size for this particular event. If I downsize the resultant slide, and then later resize it back up to the 1920 x 1080 ... is there any loss of resolution? I have this old memory of working with an earlier Photoshop, where once one downsized an image, and then resized it back up, the image retained the resolution of the downsized version ... so one always had to keep an image the same size once loaded in. I know Photoshop has a way around this now. But just wondering if it is an issue with Keynote?

B

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Answer 6

Jun 10, 2016 9:55 AM in response to Ben Low

If I downsize the resultant slide, and then later resize it back up to the 1920 x 1080 ... is there any loss of resolution?

Pixel size in Keynote and pixel size of image files are different things:

Example 1

If you reduce the pixel count of an image that is 1920 x 1080 pixels (File 1), to 1280 x 720 and resample and save as (file 2), you will be throwing away pixels / image data, thus degrading the image resolution.

If you then change the pixel size of (file 2) back to of 1920 x 1080 pixels and resample, the resultant file will have less visual resolution than the original image, even though the pixels are now the same as the original. Those missing pixels can't be recovered. This applies in what ever image editing application whether Photoshop, Preview, Pixelmator etc.

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Answer 7

Ben Low Author

Level 1

112 points

Jun 10, 2016 10:38 AM in response to Gary Scotland

But if I DON'T save ... meaning if I am just continuing to work on the document ... the file is only converted to the reduced pixel version when I save? Have I got that right? And, if I decide down the line to make the image bigger again ... then I should go back to the original and re-import it back into the Keynote?

Just to be sure I've got this right...

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Answer 8

Jun 11, 2016 3:07 AM in response to Ben Low

But if I DON'T save ... meaning if I am just continuing to work on the document ... the file is only converted to the reduced pixel version when I save?

For image files; if the pixel resolution and resample is selected the image will be changed at that point, but the file will not retain the changes until the file is saved.

if I decide down the line to make the image bigger again ... then I should go back to the original and re-import it back into the Keynote?

Yes correct, a good work flow for any kind of file (text, images, video, Keynote);

keep the original unchanged as an archive file,
make a copy of the original to use as the working version,
make changes in the working copy saving a separate file of that change,
keep the working copy unchanged,

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Answer 9

Ben Low Author

Level 1

112 points

Jun 11, 2016 6:15 AM in response to Gary Scotland

Thank you again Gary. Very clear. Very helpful. We are just getting going here. I'm working with a PC guy, it's his presentation, but we have to deliver the final output as a Keynote because the people running the conference are all Mac based and everything is being streamed out from that Mac setup. A lovely setup by the way ... running all the presentations for about 35 speakers, at least four mega-LCD-screens in the hall, the sound system, and streaming out to the web ... all done with one Mac Pro (the cute little round black thingie). The techie guys were amazed last year at how much they could have running off that one unit without crashing.

I have to supply the images, he builds the presentation in PC Powerpoint, then I have to prettify the end result in Keynote. Thank God Keynote does such a seamless back and forth with Powerpoint.

Thanks mucho again,

Ben

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