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.

  • \$\begingroup\$ 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. \$\endgroup\$
    – mattdm
    Mar 2, 2014 at 6:13
  • \$\begingroup\$ 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? \$\endgroup\$
    – mattdm
    Mar 2, 2014 at 6:20
  • \$\begingroup\$ 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. \$\endgroup\$
    – mattdm
    Mar 2, 2014 at 6:27
  • \$\begingroup\$ mattdm, you're not being difficult at all. On the contrary, you're forcing me to examine my assumptions, which is good. I added an "EDIT 3" to the question. Please take a look. And, yes, I will go through the question you linked. Thanks very much. \$\endgroup\$ Mar 2, 2014 at 8:03
  • \$\begingroup\$ completely useless comparison. As long as they look the same at the size you're interested in, how they look when pixel peeking is utterly irrelevant. \$\endgroup\$
    – jwenting
    Mar 3, 2014 at 7:50

1 Answer 1


iPhoto and Picasa are discontinued products. It past time to switch to a different image viewer if you haven't already done so.

Keeping the same zoom level while browsing photos does not appear to be possible in both iPhoto and Picasa. However, in both programs, you can press 1 to zoom to 100%.


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