iPhone Photography Tip: Using One Picture For HDR


In one of my previous posts I talked about HDR Photography using Pro HDR. As you may recall one of the options is to chose two pictures from within your photo library and combine them.

As I mentioned, not a lot of people go around taking a picture that’s under exposed and over exposed for the same scene. Also, sometime you don’t have time to take two pictures. But even with one photo, you can still turn it into an HDR picture.

All you need is an app that allows you to edit a pictures exposure. I use Photoshop Express. It’s free.

Open the picture you’d like to use. Along the top tap the symbol that looks like a sun, and pick exposure.

Use your finger to slide to the left to darken the picture. This will ensure your bright areas retain detail. Once you’re happy with the result save the picture to your photo library.

Next you’ll want to chose the same picture again. Make sure it’s the original, and not the edited one you just saved. Select exposure again, but this time slide your finger to the right. This will bring out the highlights in the dark areas. Again, once you’re happy with the results save the picture.

Once that’s done, you can run Pro HDR using the Library HDR selection and follow the instructions.

Using this method also ensures your pictures line up perfectly and I’ve found that in many cases, the resulting HDR pictures looks better.


  • Oclement

    That can’t really be called HDR
    Might be an “efficient” method (in some cases) to simulate the effect, but there’s no way you’ll get the same amount of infornation in the resulting picture as yoi have much less information to start with.

    Changing the exposure will not reveal details the camera missed while taking he shot because of a wrong exposure.

    I guess this is the exact method that the other apps were using prior the release of pro hdr abd the likes of it, using a single picture.

    Just my 2cents

  • Flaxx

    Hi Oclement,I disagree with you. It’s not HDR in the sense that it’s still an 8-bit per color image, rather than 10/16/32 bit per color image, but it certainly has more visual information than either of the two original images because the first has the background and the second has the foreground. The effective range is much more than 8-bit per color, but it is then compressed (mapped) into the 8-bit per color space. It’s no different than, adding the two images together to make a 16-bit per color image, removing the over-exposed and under-exposed sections of each respective picture, and then saving it as an 8-bit per color image (thus compressing the color-space). That’s why they’re called HDR images and not just HR. Keep in mind too, that the monitor you’re using (or at least what most people are using), probably only displays 6-bits per color which is why you wouldn’t see a difference between a true HR image and an HDR image.

  • I disagree in your disagreement 🙂
    Whatever you took as overexposed can never be corrected enough to achieve the same result as a correctly exposed photo, no matter which software you use. You just can’t create data out of thin air, nor the computer can.

    With a RAW photo, taken with a Good DSLR, you’ll be able to use this method to create 2+ exposed pictures, and will achieve acceptable to good result using this technique, but is still referred to as “Fake HDR”. The reason is simple, you’re limited by the Sensor’s ability to capture all the light variation. I think the most you can get from a DSRL (for now at least) is about 11 Stops, so you’ll be limited to that. 3 Pics taken separately, even with a cheaper sensor will merge into a pic with a range of 14-15 Stops.

    Now, there’s no way an iPhone can take a single pic with that many informations, the sensor being a CMOS, its dynamic range is by nature smaller than what a CCD will provide, usually found in the DSRLs.

    I’m not saying CMOS or iPhone can’t achieve HDR or make great photos, but my point is that there’s no way you can have enough input/output with a single photo taken with a camera phone (no matter its quality) to create what would be a true HDR photo.

    (had a hard time putting my ideas together, sorry if it’s confusing at time, I’m trying to work at the same time hehe 😀

  • Flaxx

    I think you’re failing to understand how HDR works. You don’t modify a single picture, because of course a single picture is limited to the data that is already there. With HDR you are combining several different pictures taken with several different exposures. In this article, the idea is, one picture has the detailed information of the background and the other has the detailed information on the foreground. Combine them together (respectively removing the foreground and background) and you get an HDR image that would be IMPOSSIBLE to capture with the sensor it was captured on because effectively you’re taking a shot that is half exposed with a slower shutter and half exposed with a faster shutter…
    They have a good example image with the middle image being a “best exposure” capture and showing you that the HDR still gets a “better” image because it has better captured a range that the sensor is physically unable to do.

  • Bugten

    I have to agree with Olivier. I don’t see how you can create details that are missing in a photo by underexposing and overexposing the shot. If you try this with your favorite photo editing software, you’ll see that it works to a small degree, but it will never compare to taking actual bracketed shots.

  • Jgates513

    I’m not seeing a Save As… option. Not sure how to save it and still load the original back.

  • I do understand how HDR works; but the article is really about taking a single shot, and simulating different expositions in a photo editing software …

  • I do understand how HDR works; but the article is really about taking a single shot, and simulating different expositions in a photo editing software …

  • guylegend

    I don’t care whether this is true HDR or not but the results look pretty darn good. I mean I like the last image a lot better than the original and isn’t that what we’re after here? I get the sense that people care more about methods than actual results. This is art people!

  • +1

  • Brian

    This is like adding hiss and pops to a 128 bit MP3 and saying it sounds just like the original vinyl would sound. It’s complete crap, but people are told that HDR photos are good, and this has similarities to an HDR photo so hey, this must be good too, right? Maybe it’s a fun little toy to fool around with, but let’s not make it any more than that.

  • Flaxx

    Ugh! I feel like an idiot. You’re totally right and I completely agree. I was thinking you were talking about when you have multiple shots and combine them, that it would not be HDR. Clearly in the context of this article (when there is only a single shot for the source of the two images), I agree with you (and in fact in my last reply, I wrote “You don’t modify a single picture, because of course a single picture is limited to the data that is already there.”). Sorry for the misunderstanding.