Viewing a Photo at 100%

[Tobman]

Just a minor technical question. Often others refer to viewing an image at 100% onscreen in your computer. What does that mean, 100% of what?

[steve welle]

Good question and maybe not everyone means the same thing. I take it to mean that the number of pixels used to display the picture on your screen is the same as the number of pixels in the image file. For example, if your JPEG is 1000 pixels wide and your computer screen is 2000 pixels wide it would take up half the width of your screen viewed at 100%. I am sure I will be corrected soon if that is not how most photographers interpret 100%.

[Shadowman]

Most software editing programs (at least Photoshop versions) automatically zoom to 100% (default setting) for sharpening and noise reduction. You'll see the popup screen when you launch that application. With ACR you have to manually zoom in to view at range you desire. I've read where 50% zoom is just as effective.

[Manfred M]

Most modern cameras take pictures at considerably higher resolution than your computer screen is capable of displaying. A typical display is 1920 pixels wide x 1260 pixels high. A camera has a significantly higher resolution; for instance mine has a native resolution of 7360 x 4912 pixels. In order to display the entire image on my computer screen, a lot of the data in the image file is "thrown away" to get the image to fit (this is referred to as downsampling) and it really means what you see is only a portion of what your camera was able to capture. To make things worse, this dpwnsampling operation tends to show the image as being sharper than it really is.

By looking at an image at 100%, you will only see part of the image, but without any alteration of the data. In general, this image will not be as sharp as it should be if you are looking at something reconstructed from a RAW file (jpegs will have in camera sharpening and contrast adjustement, plus any other settings dialed in).

So, if we can't see the whole image cleanly on our screens; why do we bother with those large mega-pixel cameras? If we post SOOC images on the internet; and do no manipulation to the images, that would indeed be the case, but if we do prints, the resolution of a printer is far higher than a screen and even for moderate print sizes, the image has to be upsampled (a nice way of saying we have to create pixels where there are none), so in reality, we need to make print decisions based on the size of the final print size.

[dje]

Just a minor technical question. Often others refer to viewing an image at 100% onscreen in your computer. What does that mean, 100% of what?

Toby it's a term that IMO can be a bit confusing. It simply means that one individual pixel in the display corresponds to one individual pixel in the image file - a one for one representation. Ie no upscaling or downscaling. If the pixel count in the image file is greater than in the display, only part of the image will be seen.

Dave

[Tobman]

Excellent responses, that makes perfect sense now. I guess I also didn't realize that the computer was up or down sampling, but of course it has to. Thanks!

[NorthernFocus]

...A typical display is 1920 pixels wide x 1260 pixels high....

1920x1080 seems to now be the more or less "standard" in the US to match flat screen television formats. Also referred to as "full HD" or 1080p.

[chauncey]

I also didn't realize that the computer was up or down sampling, but of course it has to

Aah...I don't think that I would refer to it as up/down sampling as there is no change to the image size.

[ajohnw]

I suppose the term 100% crop is a bit odd. It basically means cropping a full sized camera image down to a size suitable for displaying on a pc screen so the 1:1 screen pixels to camera pixels still holds after a fashion. Often used for pixel peeping as an indication of lens quality. This can happen when the subject of a photo doesn't come anywhere near filling the camera's frame. Small birds that are really too far away spring to mind. People often reckon that once they have an even longer lens the birds just move further away.

I have sometimes posted 400% crops. They have been magnified on a PC screen by a factor of 4 not physically up scaled to a larger size. A sort of poor man's quick lens test.

John
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[NorthernFocus]

Aah...I don't think that I would refer to it as up/down sampling as there is no change to the image size.

Depends on which image you are refering to. The one stored on the media or the one displayed on the computer. Unless there is a perfect resolution match, then the image has been resized/resampled for display.

[Manfred M]

Aah...I don't think that I would refer to it as up/down sampling as there is no change to the image size.

From a technical standpoint, there is a real, but temporary change in size of how the image is displayed; so the updampling or downsampling does indeed take place. The fact that we have decided to not make this permanent is largely irrelevent, because we the photographer make decisions based on the displayed image.

If we then go ahead and use these tools to save the file to a smaller size for posting on the internet or elsewhere, then we either overwrite the existing file or create a new one.

[NorthernFocus]

One feature missing in LR that exists in PS Elements is the ability to view the image "print size". Though the translation isn't perfect, you can display a scale on screen and simply use a rule to tweak up/down as necessary.

My typical workflow is to do any necessary noise reduction and capture sharpening at 100% resolution. Then final print sharpening displayed at "print size". It's not perfect but I find it useful. Of course for web use final sharpening should be done at the resoluiton the image will be displayed at.

[Stagecoach]

One feature missing in LR that exists in PS Elements is the ability to view the image "print size". Though the translation isn't perfect, you can display a scale on screen and simply use a rule to tweak up/down as necessary.

Dan,

The function in Elements to view the "print size" on screen is one I use often but it was some time before I realised that to get it to display dimensionally accurate on screen it was necessary to enter the exact 'screen resolution' figure within the 'units and rulers' preferences within the edit menu.

Grahame

[NorthernFocus]

...to get it to display dimensionally accurate on screen it was necessary to enter the exact 'screen resolution' figure within the 'units and rulers' preferences within the edit menu.

Thanks, I'll take a look at that.

[animalnz]

Unfortunately the ability to view a print at actual size has been removed from later versions of photoshop. Discussions I have read elsewhere suggests the decision was made because, as stagecoach has pointed out, many people did not realize that a small amount of setup is necessary to get it right. I would have thought a little education (maybe a pop up warning of the problem) was a better solution but I don't pay the support salaries at Adobe.

[Manfred M]

Unfortunately the ability to view a print at actual size has been removed from later versions of photoshop. Discussions I have read elsewhere suggests the decision was made because, as stagecoach has pointed out, many people did not realize that a small amount of setup is necessary to get it right. I would have thought a little education (maybe a pop up warning of the problem) was a better solution but I don't pay the support salaries at Adobe.

Seriously?

I can think of three different ways I do it with Photoshop CC (same as CS6). I suspect there are more.

1. <Image> <Image Size> menu items. Choose the paper size, resolution (360 dpi for Epson printers and 300 dpi for all others). You can also select the resampling algorithm from the dropdown menu.

2. You can also use the same menu and change the canvas size and drag your image to fit; and

3. <File> <New> then select the paper size from the dropdown box, select the colour model and print resolution. Drag or copy and paste your image and use the transform tool to resize.

To view at 100%, double click on the maginifying glass icon or type in the 100% on the bottom left corner of your screen. I do this when I do my output sharpening.

[animalnz]

All true except that in earlier versions of photoshop I could view at print size , after calibrating once for my screen, by clicking on the, conveniently labeled, view at print size button. No resizing, and then revert at will, and even back again all with the same convenient button.

[Giman]

I don't know where I learned it, but I was told that PS can only render a precise image preview representation in 100%, 50%, 25% or 12.5% views. In earlier versions only 100% view would render a preview of sharpening effect. I notice that CC can render a preview at any magnification. PLEASE CORRECT ME IF WRONG but why not view a magnification closer to the desired finish print size to check on noise and sharpening effect?

[Manfred M]

I don't know where I learned it, but I was told that PS can only render a precise image preview representation in 100%, 50%, 25% or 12.5% views. In earlier versions only 100% view would render a preview of sharpening effect. I notice that CC can render a preview at any magnification. PLEASE CORRECT ME IF WRONG but why not view a magnification closer to the desired finish print size to check on noise and sharpening effect?

The last number of versions of Photoshop have had good precise rendering at any size. I think this started around CS3, but I cannot remember for sure.

The magnification I use definitely depends on what I am doing in post. Output sharpening is always done at 100% of the final size; otherwise we cannot get an accurate representation as to what the impact will be on the image. If I am doing a complex selection with the pen tool, I may zoom in to 400% or even more, if I am doing certain other functions like resizing, I may be viewing at 10% or 15%