How to Match Exposures when Stitching Panoramas in Photoshop - Digital Photography School
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How to Match Exposures when Stitching Panoramas in Photoshop

Since the introduction of Photoshop CS2, Adobe’s image editing software has shipped with the ability to easily merge a series of photographs into a panorama.  Often, it is incredibly simple: once you have the images you want to stitch together, it only takes a few clicks to produce the blended panorama.  However, whilst Photoshop may be able to seamlessly merge your images 90% of the time, on occasion it may struggle to perfectly match the exposures across the input images resulting in a final panorama with obvious joins between the individual photographs.

To see what I mean, have a look at the image below.  This is a 7 shot panorama, straight out of Photomerge, and you can see obvious banding in the water of the lake, as the exposure/colour tone subtly change between images.

panorama_exposure_match_image-3

Top: The panorama fresh out of Photomerge. Bottom: I've highlighted the joins between the individual input images where the blending of exposures was not sufficient

This article walks through a series of fairly simple steps to edit the above panorama to remove the obvious joins and give a perfectly blended panoramic image  (note: I am only going to discuss processing the panorama once it has been stitched by Photomerge.  For tips on how to take the images, prepare them for stitching and on use of Photoshop to stitch them, see this recent article by Jason Weddington).

It is worth mentioning that the images I started with were a challenge to shoot for a panorama as the exposure differed greatly between the far left of the image, where I was shooting away from the sun, and to the far right, where I was shooting towards the sun.  Therefore, before blending the images into the panorama, the individual images were processed in Adobe Lightroom to try and match the exposures as closely as possible first.  Once complete, the selected images were exported to Photoshop to ‘merge as a panorama’, using the ‘auto’ setting.

On to the steps…

1.  Once the images have been merged, the output image will consist of several layers (one for each input image, in this case 7) with a mask applied to each layer.  In many cases, these layers can be flattened at this point to give the final panorama, however, we’re going to make a few edits first.

panorama_exposure_match_image-2

2.  Create a new layer, on top of all other layers.  Fill the layer (Edit > Fill) with 50% grey:

panorama_exposure_match_image-4

3.  Set the blending mode of the ‘grey layer’ to ‘overlay’.  When set to overlay, a 50% grey layer will appear transparent, so initially this layer will make no difference:

panorama_exposure_match_image-5

4.  Find one of the joins where the exposure needs to be tweaked, for example, below, there is an obvious join between the two images.  The left hand image needs to be a little lighter and the right hand image needs to be a little darker.  Let’s address the left hand image first.

panorama_exposure_match_image-6

Only the two layers of interest are selected here. The left hand image needs to be lightened, whilst the right hand image needs to be darkened

5.  If we ctrl+click/cmd+click the mask of the appropriate layer (i.e. click on the black/white rectangle in the layer bar), we will bring the portion of the image to be edited into an active selection (we only want to edit inside of that selection for the time being).

6.  Ensure the ‘grey layer’ is highlighted

7.  Select the brush tool.  You will want a large, soft brush so set the size to be a few hundred pixels (I used 500 px in this instance, but the size is relative to the size of your panorama) and set the hardness to 0%.  Set the opacity to 3% and the flow to 20%:

panorama_exposure_match_image-7

8.  To lighten the layer we want to select the colour white (if we wanted to darken the layer, we would select black).

9.  Using the brush, liberally brush over the join and back towards the centre of the image.  This will paint white onto the grey layer, but only within the current selection.  As the brush is very soft the edits should be subtle, but as you brush you should be able to see the area under where you have painted white gradually begin to get lighter.

panorama_exposure_match_image-8

An active selection of the mask of the left hand image is required so that any edits are only applied within that selection. The idea is to paint white onto the 'grey layer' in the region highlighted by red in the above image.

10.  In order to get seamless joins, I find that is is a compromise between lightening one image and darkening the other in order to maintain a smooth transition of tone/exposure across each image.  Therefore to edit the right hand image, you repeat steps 5 to 9, but ensure that the right hand image is within your active selection, and that the colour black has been selected for your brush.

Initially it is a slow process that involves carefully modifying each image at the join in order to match the exposure, however once you get a feeling for the brush it can become quite quick.

If we change the blend mode of our ‘grey layer’ back to ‘normal’ you will be left with something similar to the middle image below, where you can see the result of the white/black brush strokes on the grey layer and the difference it makes to the actual join.

panorama_exposure_blending_9

A composite showing the starting image, the modified 'grey layer' and the final image, when the 'grey layer' is set to 'overlay'.

If you repeat that for each join across the panorama, you will end up with grey layer that looks like the image below (with the blend mode set to ‘normal’).

panorama_exposure_match_image-10

The 'grey layer' for the entire panorama showing the white/black brush strokes around each join

Once you set the blending mode back to ‘overlay’, all of the joins should disappear, and you should be left with a perfectly blended panorama with no tell tale signs of the joins:

panorama_exposure_match_image-11

The entire panorama when the 'grey layer' is set to 'overlay'. The joins between the images are no longer visible in the water of the lake

As the edits have been made to the ‘grey layer’ no permanent edits have yet been made to the actual images, so any mistakes are easily rectified or any further modifications can easily be made.  Once you are happy with the blending of the individual images, you can flatten the layers to produce your final panorama and make any further finishing touches:

panorama_exposure_match_image-12

The final panorama: Llyn Cregennen, North Wales, UK

I hope those steps were easy enough to follow.  Ultimately, this is just one application of a the use of a 50% grey layer, set to ‘overlay’, in order to modify the exposure of an image in a non-destructive manner (until the layers are flattened, that is).  So if you try to blend a panorama in Photoshop but didn’t quite get the results you were after, you dont have to jump for the clone brush straight away or send the image to the trash.  Give these steps a try and see if you can manually match your exposures where Photoshop can’t.

Please let me know if you have any feedback, I welcome any comments and, as always, I’ll try to respond when I can.

 

 

 

Read more from our Tips & Tutorials category.

Elliot Hook is a wildlife and landscape photographer based in Hertfordshire, UK. Elliot loves being outdoors with his camera, and is always looking to improve his own photography and share what he has learnt with others. Elliot also can be found at his website, on Twitter, Flickr and 500px.

  • http://www.crossfire.ro Ariel

    I was looking for something like that in order to avoid those 3rd party panorama softwares (pricey ones) that do this automatically.

    PS: try Microsoft ICE tool (free – http://research.microsoft.com/en-us/um/redmond/groups/ivm/ice/ ) for some panorama merging that sometimes are better than default PS.

  • http://www.os-am.com OsmosisStudios

    Or get it right when shooting?

  • Lon

    Shoot in manual.

  • Darbraun

    I agree with Osmosis, panos need to be shot on manual with NO change in exposure, avoiding painful post processing repairs.

    If your light changes during shooting, start over.

  • chauncey

    That’s a great tutorial but…yeah there’s always a “but” isn’t there…it presupposes that simply re-running photomerge will not automatically fix the problem.
    also…photoshop has six different methods for photomerging and they all cough out different results

  • ccting

    excellent..

  • http://blog.tonyeveling.com/ Tony

    Osmosis Studios – He has got it right when shooting. The exposure differences in his example are tiny and within normal margins of error. In fact some of this ‘wrong exposure’ will/may be down to naturally occurring vignette effects due to the lens (regardless of lens quality) A tiny difference caused by natural and unavoidable vignetting (and not noticeable in single images) can/will/may cause the differences in ‘exposure’ that you see in his example.

  • Matt Photodocumentarian

    Very nice tutorial. Too many Photographers are egomaniacs and it’s a shame some can’t just simply be more complimentary or not say anything at all. The arm chair quarterbacks on posts like this always make me sad.

  • Paul

    I think he has done a great job in explaning a technique to fix the trouble areas. I can usually get a fairly decent result fixing the light but its the water patterns and waves which give me the biggest headache. Even the above example still have reflection and wave pattern issues…but I guess that’s just another piece of the puzzle when you have moving elements in a multishot panorama :)
    Thanks for the great tutorial!

  • http://www.aaanouel.com aaanouel

    What I do is to create a new layer painted with linear gradient and different gray values (50% to Zero and/or intermediate values in between) according to the Pano I want to fix.

    Set layer to Overlay or Multiply (the same but inverse), playing with Opacity%, repainting the gradient and/or moving it L&R until it correctly fixes the Pano as well as possible.

    Finally, applying some big and very soft (Screen and/or Multiply mode) airbrush strokes (with minimal strength and flow) to retouch.

    For water seams I use a tiny Clone Stamp (totally horizontal copy) by applying an horizontal movement and frequently changing the cloned point for not repeating any patron.

  • nicolopicolo

    Very good results for panorama shots with ICE from Microsoft. For a free software is one of the best tool for novice and experienced user. User friendly and very good quality output.
    This image was created from 3 shots, manual settings and tripod.

    http://www.flickr.com/photos/33385365@N08/7621727828/in/set-72157627119816779/

    If interested download from this link bellow

    http://research.microsoft.com/en-us/UM/redmond/groups/IVM/ICE/

  • http://www.os-am.com OsmosisStudios

    Tony: WHY ARE YOU TYPING IN BOLD?! Your comment would have been better received had it been written normally and not like that of a 14 year old girl.

    That aside, there are ways of correcting natural vignetting when doing the panorama that the author doesn’t even show. The methods used in Photomerge aren’t shown, so we can’t see how that was done: Checking a single checkbox can, in 99% of cases, remove this issue entirely. There are also other applications that can do a much better job straight out the box without fiddling. Finally, while many lenses have vignetting as severe as this wide open, it is most often eliminated with stopping down a few stops to the f/8-11 range, which is where most landscape photos are taken anyway. In fact, I’d challenge you to find a lens that doesn’t have it’s vignetting (especially of this intensity) removed by stopping down. At which point I’ll tell you not to buy that lens.

  • http://www.elliothook.co.uk Elliot Hook

    @OsmosisStudios – let’s keep this good-natured, I’m sure Tony’s post was a just a formatting error.

    For your info, the input images were taken in ‘manual’ at f/11, ISO100, at ~50 mm, each exposure was 1/10th second. The effect observed here isn’t due to vignetting and you can see that actually the exposure matches more or less perfectly for the land in the image, but it struggles with the water, even well into the centre of the frame in some instances (ticking the ‘remove vignetting box, actually makes the joins more obvious!).

    My best guess is that the small differences in the brightness of the water is due to the angle of the camera changing as it moved through the panorama causing the reflected light being recorded by the sensor to differ very marginally. Either way, to linger on that point is to miss the point of the article, which was to show one example of how to correct for this aberration, and achieve a well matched panorama. I’m certain there are other ways to do it, but I could not find an automated panorama stitcher that could do a better job, hence why I thought it would make a good tutorial in case others came up against a similar scenario.

  • viragored

    Neat fix, well explained – thanks. Another tip when shooting is to use fixed white balance, not auto.

  • http://www.os-am.com OsmosisStudios

    Elliot: Yes, because somehow tony managed to use a bold tag and a italic tag accidentally…

    I’m going to guess you used a circular polarizer?

  • http://www.elliothook.co.uk Elliot

    No circular polarizer, just a graduated ND filter.

  • http://www.pixbeatphoto.com Chris

    Ignore the haters. Thanks for the post and the tips! Look forward to reading more.

    -CB

  • tureluur

    Thanks, cool trick.
    I am always messing with the dodge and burn tool. (oh oh primitive)

  • Bruce

    Wouldn’t it simply be easier to check the Blend Images Together when doing the Photomerge initially?

  • http://www.courier-spain.com Edmund Sykes

    I read more blogs than I shoot photos (how sad is that?) but this is the best I have ever read. Many thanks for wonderful advice on a Photoshop technique I hadn’t even considered.

  • Mike

    Good info, but it’s kind of a shame that you have to know more about computers and software these days then actual photography.

  • mystixa

    “actual photopraphy” always depended on techniques like this to get to the image you see. The photoshop tools we use today are simpler to use for greater effect then those used in the darkroom. ..but they didnt invent the manipulations. A lot of what Ansel Adams did for example was accomplished in the dark room as much as it was on the tripod.

Some older comments

  • Edmund Sykes

    April 20, 2013 01:35 pm

    I read more blogs than I shoot photos (how sad is that?) but this is the best I have ever read. Many thanks for wonderful advice on a Photoshop technique I hadn't even considered.

  • Bruce

    March 4, 2013 03:37 pm

    Wouldn't it simply be easier to check the Blend Images Together when doing the Photomerge initially?

  • tureluur

    February 19, 2013 08:51 pm

    Thanks, cool trick.
    I am always messing with the dodge and burn tool. (oh oh primitive)

  • Chris

    February 12, 2013 12:53 pm

    Ignore the haters. Thanks for the post and the tips! Look forward to reading more.

    -CB

  • Elliot

    February 12, 2013 12:38 am

    No circular polarizer, just a graduated ND filter.

  • OsmosisStudios

    February 12, 2013 12:29 am

    Elliot: Yes, because somehow tony managed to use a bold tag and a italic tag accidentally...

    I'm going to guess you used a circular polarizer?

  • viragored

    February 11, 2013 07:54 am

    Neat fix, well explained - thanks. Another tip when shooting is to use fixed white balance, not auto.

  • Elliot Hook

    February 11, 2013 04:25 am

    @OsmosisStudios - let's keep this good-natured, I'm sure Tony's post was a just a formatting error.

    For your info, the input images were taken in 'manual' at f/11, ISO100, at ~50 mm, each exposure was 1/10th second. The effect observed here isn't due to vignetting and you can see that actually the exposure matches more or less perfectly for the land in the image, but it struggles with the water, even well into the centre of the frame in some instances (ticking the 'remove vignetting box, actually makes the joins more obvious!).

    My best guess is that the small differences in the brightness of the water is due to the angle of the camera changing as it moved through the panorama causing the reflected light being recorded by the sensor to differ very marginally. Either way, to linger on that point is to miss the point of the article, which was to show one example of how to correct for this aberration, and achieve a well matched panorama. I'm certain there are other ways to do it, but I could not find an automated panorama stitcher that could do a better job, hence why I thought it would make a good tutorial in case others came up against a similar scenario.

  • OsmosisStudios

    February 11, 2013 01:37 am

    Tony: WHY ARE YOU TYPING IN BOLD?! Your comment would have been better received had it been written normally and not like that of a 14 year old girl.

    That aside, there are ways of correcting natural vignetting when doing the panorama that the author doesn't even show. The methods used in Photomerge aren't shown, so we can't see how that was done: Checking a single checkbox can, in 99% of cases, remove this issue entirely. There are also other applications that can do a much better job straight out the box without fiddling. Finally, while many lenses have vignetting as severe as this wide open, it is most often eliminated with stopping down a few stops to the f/8-11 range, which is where most landscape photos are taken anyway. In fact, I'd challenge you to find a lens that doesn't have it's vignetting (especially of this intensity) removed by stopping down. At which point I'll tell you not to buy that lens.

  • nicolopicolo

    February 8, 2013 09:59 am

    Very good results for panorama shots with ICE from Microsoft. For a free software is one of the best tool for novice and experienced user. User friendly and very good quality output.
    This image was created from 3 shots, manual settings and tripod.

    http://www.flickr.com/photos/33385365@N08/7621727828/in/set-72157627119816779/

    If interested download from this link bellow

    http://research.microsoft.com/en-us/UM/redmond/groups/IVM/ICE/

  • aaanouel

    February 8, 2013 04:40 am

    What I do is to create a new layer painted with linear gradient and different gray values (50% to Zero and/or intermediate values in between) according to the Pano I want to fix.

    Set layer to Overlay or Multiply (the same but inverse), playing with Opacity%, repainting the gradient and/or moving it L&R until it correctly fixes the Pano as well as possible.

    Finally, applying some big and very soft (Screen and/or Multiply mode) airbrush strokes (with minimal strength and flow) to retouch.

    For water seams I use a tiny Clone Stamp (totally horizontal copy) by applying an horizontal movement and frequently changing the cloned point for not repeating any patron.

  • Paul

    February 8, 2013 03:29 am

    I think he has done a great job in explaning a technique to fix the trouble areas. I can usually get a fairly decent result fixing the light but its the water patterns and waves which give me the biggest headache. Even the above example still have reflection and wave pattern issues...but I guess that's just another piece of the puzzle when you have moving elements in a multishot panorama :)
    Thanks for the great tutorial!

  • Matt Photodocumentarian

    February 7, 2013 01:58 am

    Very nice tutorial. Too many Photographers are egomaniacs and it's a shame some can't just simply be more complimentary or not say anything at all. The arm chair quarterbacks on posts like this always make me sad.

  • Tony

    February 4, 2013 11:01 pm

    Osmosis Studios - He has got it right when shooting. The exposure differences in his example are tiny and within normal margins of error. In fact some of this 'wrong exposure' will/may be down to naturally occurring vignette effects due to the lens (regardless of lens quality) A tiny difference caused by natural and unavoidable vignetting (and not noticeable in single images) can/will/may cause the differences in 'exposure' that you see in his example.

  • ccting

    February 4, 2013 02:56 pm

    excellent..

  • chauncey

    February 3, 2013 11:44 pm

    That's a great tutorial but...yeah there's always a "but" isn't there...it presupposes that simply re-running photomerge will not automatically fix the problem.
    also...photoshop has six different methods for photomerging and they all cough out different results

  • Darbraun

    February 3, 2013 04:07 pm

    I agree with Osmosis, panos need to be shot on manual with NO change in exposure, avoiding painful post processing repairs.

    If your light changes during shooting, start over.

  • Lon

    February 3, 2013 03:34 pm

    Shoot in manual.

  • OsmosisStudios

    February 3, 2013 07:28 am

    Or get it right when shooting?

  • Ariel

    February 3, 2013 03:15 am

    I was looking for something like that in order to avoid those 3rd party panorama softwares (pricey ones) that do this automatically.

    PS: try Microsoft ICE tool (free - http://research.microsoft.com/en-us/um/redmond/groups/ivm/ice/ ) for some panorama merging that sometimes are better than default PS.

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