What Is Canon's Auto Lighting Optimizer?

What Is Canon’s Auto Lighting Optimizer?


As camera manufacturers started realizing the limits of digital camera sensors, they started trying to increase their range. Today’s sensors have a range of around 7-9 stops of light, depending on the manufacturer. It is said, at any given point in time, the human eye can see about 14 or 15 stops of light. This difference between what we see and what a camera sensor ‘sees’ is the gap technology has been trying to fill, both in terms of absolute range on the sensor and manipulation techniques once the image is captured.

On Canon cameras there is a feature called Auto Lighting Optimizer (ALO). On Nikon cameras the aproximate same feature is known as Adaptive D-Lighting. Other cameras have the same basic feature. While the names are different, the idea is the same; increase the dynamic range presented in the final image.

The Canon Auto Lighting Optimizer functions by bringing out shadow detail as I will show in the following photos. All the photos are cropped down to show the same area and lighting. Lighting was constant and a manual setting of ISO 100, f/11, 1/400 was used on a Canon 7D and Canon EF-S 10mm-22mm lens. The pictures progress from the ALO being Disabled, then Low, Standard and Strong. Note: this function only affects JPEG images as RAW images are intended to give an exact copy of the sensor information. To help with detail, all images were increased by 1 stop of exposure in Lightroom, otherwise they are right out of the camera. Click on an image for a 2000px wide version.

From the first image to the last, the effect can be fairly useful. Notice, however, that the sky in the upper left becomes just a bit more blown out because of the overall dynamic range in the shot. To help give some more data, here are the Histograms from the pictures, in order.

The Histograms show where those highlights are nearing the edge on the right as well as how the dark areas have been marched over as well. There also seems to be a much larger jump from Standard to Strong as evident in the intensity of the light measured.

For those who shoot in JPEG, you may want to experiment with your cameras Auto Lighting Optimizer, Auto D-Lighting or whichever name your camera manufacturer gives this feature. It can be helpful but it is important to know it’s limitations.

Read more from our category

Peter West Carey leads photo tours and workshops in Nepal, Bhutan, Seattle, Portland, Los Angeles and beyond. He is also the creator of Photography Basics - A 43 Day Adventure & 40 Photography Experiments, web-based tutorials taking curious photographers on a fun ride through the basics of learning photography.

Some Older Comments

  • Danny May 14, 2013 09:38 am

    Many thanks for this blog Peter, it's helped me cause I always have some problems with shadows I have the D60 and I'm hoping my pictures will improve using this feature will be having loads of playing around with it in the near future.

    Keep snapping.

  • PhotoOp March 10, 2012 03:53 am

    Histograms would be more useful if the data were laid out so that changes in the frequency of data could be adjusted in specific areas. This is what most scroll bars attempt do and what Adobe tries to do by imitating a color field and reproducing it. But all the post pro won't change a bad image into a good one. Unless your specialty is removing pimples. Cameras are costly enough that more should be expected from their metering systems. If I could e.g. check a histogram in the LCD screen and make minute changes to exposure I'd buy into the concept. But all u can do is randomly apply changes which may make the results worse.

  • Mike Fewster May 22, 2011 09:31 pm

    I wasn't directing my comment at you Peter, but at Canon. I am currently in Asia and that camera with that feature is being heavily promoted here as though it is a new breakthrough. Example. TV and newspaper and billboards with shots of the Taj in dim light, then a side by side with a shot taken with the "new" Canon feature. I have no idea how it is being promoted elsewhere.
    However, while we are discussing this, you might like to go to the Apical site, check what that process is about and compare it with the Canon process. When Apical was first used under licence by Sony, many Sony users tried to duplicate the results by just post processing tweakng the images. The general conclusion was that the apical process is not something that can be replicatd by PP tweaking, although an approximation od it can be done. I'd be interested in knowing whether this is what Canon have done or whether they have come up with an Apical type process of their own.
    Sony still seem to me to be way in front of the field in this. Their "Twilight" mode combine 6 exposures into one without blurring for extraordinary hand held low light results, they also have the option of the Apical or regular bracketing approaches.

  • Bridget Casas May 22, 2011 08:45 am

    I prefer to shoot in Raw. So I see how HDR could be used for this type of photo. Thank you for the info.

  • Peter West Carey May 22, 2011 02:39 am

    I think you're taking things out of context a bit. Canon isn't trumpeting this feature, I simply wrote a post about it so others, who may not know about it, can learn. The same way there are posts on DPS about the Rule Of Thirds, which is also not new.
    Nowhere did I mention that this feature is new, with or without apostrophes surrounding it.
    Yes, other manufacturers have similar features, but that's not what this post is about.

  • Peter West Carey May 22, 2011 02:34 am

    HD Camera Team, that is good to know the 5D Mark II allows both.

  • HD Cam Team May 21, 2011 11:21 pm

    Well, actually this is not "new" to Canon... It was introduced in 2008.

    Here there is a nice article at CPN, with some details and a list of cameras including that feature:


  • Mike Fewster May 21, 2011 08:53 pm

    This is only "new" for Canon. Sony, nikon and Olympus have been using the patented Apical process to do this for some years. The Apical process doesn't tweak the curves, it essentially allows individual pixels in a shot to have differing iso levels. Sony top end cameras use Apical best as they have a dedicated chip installed just for Apical. The lower end cameras that use the process use a somewhat simplified form. Check the Apical homepage for details on how the process works and who is using it.
    It has always surprised me that Sony, Nikon and Olympus haven't made more of this feature, so it iskind of funny that now that Canon has finally cauggt up they are trumpeting the feature.
    It is also worth checking the "Twilight" mode on some Sony models. Combined with the extrawide DR of newer Sony cameras, it makes built in flash virtually not necesary on a camera, which is probably why the Nex has only a tiny afterthought clipon flash.

  • HD Cam Team May 21, 2011 07:00 am

    Hi Peter and Jason,

    It's worth mentioning that the Canon EOS 5D Mark II allows you to use both ALO and HTP at the same time.

    We have run some tests (same scene, same camera settings with and without ALO+HTP on a 5D Mk II with Firmware 2.0.8) just to confirm it.

    Best regards.

  • Peter West Carey May 21, 2011 04:58 am

    Hey there! Highlight Priority and ALO seem to do about the same thing, in the sense of trying to expand the dynamic range and only one can work at a time (one working mainly on shadow, one working mainly on highlights). Give it a year, they both will work.

    As for the dynamic range, I was looking at some medium format camera backs today and they're up to 12-stops now. Again, maybe 2-3 years and they'll figure it out.

  • Phil May 20, 2011 01:36 pm


    The ALO feature first came out in the XSi, so the XTi missed out. Even so, it had hardly any effect in the XSi. I believe it was the T1i that first gave the option of 4 levels of ALO.

    Even though you don't have ALO, There is a similar function in Canon's Digital Photo Professional software. Under the RGB tab there are 2 tone curve assist buttons-one stronger and one weaker-which will automatically brighten up shadows.

  • HD Cam Team May 20, 2011 01:19 am

    Hi Peter,

    Thanks for posting this nice comparison. Indeed it shows the result of enabling ALO on Canon cameras.

    Obviously the negative effect is that it may bring some noise to shadows, but anyway it can be very useful in lot of shooting situations.

    Maybe people should be more polite and not so rude when posting comments. It's always easier to criticize than to spend time testing, comparing results and then writing an article :)

    Indeed, as posted in your article most current sensors (we're talking about "consumer" cameras) won't go further than 9 stops. Obviously manufacturers are working to expand that limitation (of sensors), as they have done from the firsts digital cameras.

    Thanks once again for sharing this nice test.

    Best regards.

  • Jason Racey May 19, 2011 09:49 pm

    Hi Peter. Was reading the article and noticed hey - it's you! Nice work. I just purchased a Canon D60 a few weeks ago and have been reading through the owner's manual about all the new features I have at my disposal. This is one of them.

    An interesting thing about this feature is that, at least on the Canon D60, you cannot use this and "Highlight Tone Priority" at the same time. Enabling HTP automatically disables ALO. I guess they have mutually exclusive goals. There's also couple of warnings in the manual about how these features will interfere with your ability to deliberately under- or over-expose images.

    ps. If you ever find a 14-stop camera please email me. Thanks! :)

  • Peter West Carey May 19, 2011 03:04 am

    I don't see that to be true according to DPReview http://www.dpreview.com/reviews/pentaxk5/page14.asp It shows the range closer to 8-10. Please correct me if I'm wrong.

  • Peter West Carey May 19, 2011 03:04 am

    Yes, that is the case. Yet not everyone wants to, or has to, shoot RAW. This is just another option.

  • Russ Frisinger May 19, 2011 12:39 am

    DPS, I learned something I knew absolute nothing about. Not even that it existed—and I read a Canon 7D book when I got it. This is why I follow you.



  • guzy May 19, 2011 12:02 am

    I'm curious with this feature, but after see the result I think the process is nothing more then compensate the exposure 1/3 to 1 stop over.

  • mrc May 18, 2011 11:58 pm

    For raw shooters Isn't it possible to get the same results with curves correction in raw conversion?
    I think so...


  • scott May 18, 2011 03:07 pm

    On the A700 Sony calls this the "D-Range Optimizer. I played around with it once and didn't see a significant difference, but now I'm think I may have been looking at the RAW files when I did that.....


  • Eric May 18, 2011 01:18 pm

    I suppose its worth mentioning that the Pentax K-5 has 14.12 stop of dynamic range at ISO 80, not the 7-9 listed in the article.

  • OldSailor88 May 18, 2011 07:38 am

    Is there an Auto Lighting Optimizer setting on the Canon Xti? I looked in the book but I don't see it. Thanks in advance for the assistance.

  • Tony May 18, 2011 07:35 am

    It's also worth mentioning that the there is two types of D-Lighting for Nikon shooters. Active, and regular.

    The active one affects the raw capture.