Alley in Pisa, Italy

by Lars Kotthoff

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I need to compare photos at a 1:1 pixel ratio (not downscaled to fit the monitor). For this, I need to set the view to 1:1 and then go through the photos using the arrow keys. As you can guess, I need the view setting to remain at 1:1 until I reset it, as with Lightroom.

Do iPhoto 11 and Picasa 3.9 on the Mac let me do this?

EDIT 1: This is not a Retina display. It's a 30-inch monitor at 2560 x 1600. And if I'm using a Retina display, I'd still expect the 1:1 to refer to physical pixels, no matter the pixel density. In other words, if I have a 2880 x 1800 photo, it should exactly fit the screen.

EDIT 2: To answer the question of why I am doing this, I am comparing cameras (iPhone vs NEX vs a superzoom) so that I understand exactly what the limitations of each camera are, under what situations (if any) I can leave the dedicated cameras at home and just use the iPhone, or if the superzoom gives me photo quality indistinguishable from the NEX.

EDIT 3: More information about why I'm doing this: The immediate goal is to help me decide under what circumstances the iPhone and the superzoom produce photos as good as the NEX.

This should help me decide when I can leave the other camera(s) at home and use the iPhone. Or whether I buying the aforementioned superzoom camera makes more sense for me than buying one or more zoom lenses for the NEX (each of which is as expensive as the superzoom camera).

I do not print out my photos. I view them full-screen on my monitor. So, if two cameras produce equivalent results when the photos are viewed full-screen, then I can buy the cheaper / smaller / lighter / more flexible option (like a superzoom camera instead of a zoom lens for the NEX).

The catch is that the best monitor I have today is 2560 x 1600, but I can imagine buying a 5120 x 2880 monitor. So, I don't want to choose a camera now and then realize later this year or the next year when I upgrade my monitor that my photos are not particularly good.

So, I want to compare cameras at 5120 x 2880. But my cameras take photos at a lower resolution, which is 4912 x 3264 for the NEX, and 3264 x 2448. So, I want to compare photos at 1:1 display.

(In an ideal world, if all my cameras shot at higher than 5120 x 2880, I would downscale all the images to this resolution and then compare them at 1:1. But since my cameras shoot at lower resolution, I want to compare them at 1:1. I don't want to upscale, since that reduces quality.)

Please let me know if this reasoning has a flaw. Thanks.

share|improve this question
Just to be clear, by "100%", you mean "at a 1:1 pixel ratio", not 100% of the image, right? Followup question: do you have a retina display, and if so do you want to see 1:1 pixels at that level, or actually larger? And that brings up a further followup question: why do you want to do this? –  mattdm Mar 2 at 3:37
Thanks, mattdm. Please see the updated question. –  Kartick Vaddadi Mar 2 at 4:44
To answer your last question (whether two images from different cameras have equivalent image quality), you should compare the photos at the same overall size, not at pixel-level detail. –  mattdm Mar 2 at 6:13
And, I'd like to hear more about why you answered the retina display question in that way. I agree that expecting the 1:1 correspondence to remain would be reasonable (although it turns out to not be the case in applications that don't ask for special handling), but the important question is: why do you think that adds special value in comparing images? –  mattdm Mar 2 at 6:20
I realize that I'm being a bit difficult, and I have no idea what the basic answer your simple software question even is since I don't use those programs, but I think this is really important overall. See this question about high-density displays. I know you don't have one, but it is still relevant because the basic premise is examined in the answers. –  mattdm Mar 2 at 6:27

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