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High Dynamic Range Photography

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ViperGTS-R
  • ViperGTS-R

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#1

Posted 12 May 2007 - 02:00 PM Edited by ViperGTS-R, 12 May 2007 - 02:02 PM.

user posted image


Sorry, this isnt the usual length of GTAF Tutorials, ive mainly designed this one for use my website which isnt finished yet.

Yes, it's long but hopefully you can draw out alot more knowledge out of it smile.gif

This tutorial aims to give you an idea of how HDR works and how to do it. In order to make a good HDR, a basic understanding of how HDR works is needed. Consider this tutorial to be a "For Dummies" equivalent, it's written so that anybody with a basic understanding of image editing can hopefully do it. Some more in depth tutorials can be found at:

Cambridge In Colour

HDR Soft

Luminous Landscapes

This has turned out to be a pretty long tutorial, so for people in a rush, here is my workflow in a nutshell:

In a Nutshell

* Take 3-9 exposures of the image.
* Merge them in Photoshop by using "File > Automate > Merge to HDR"
* Save as a Radiance Image (*.hdr)
* Open the HDR image Photomatix
* HDR menu > Tone Mapping
* Mess about with the settings until it looks good
* Set the preview size to 1024 (Radio buttons at the bottom)
* Take a screenshot of the preview and then exit without applying the tone mapping.
* New image in Photoshop and paste in the screenshot
* Crop, add borders etc
* Save as jpeg
* Next image...

What I usually do is merge the exposures in Photomatix first, because it is way faster, if it looks blurred or badly aligned, I merge the HDR in Photoshop, save as a HDR and tone map it in Photomatix, because Photoshop does a much, much better job at matching exposures exactly.


Introduction

First off, before I say anything, I do not claim to know a lot about photography. I have never done a course on it, or really ever gone to any great lengths to further my skills other than just to go out into the world and take some pictures and see what I can do. I am not an expert on HDR either, I taught myself how a few weeks ago and have been doing it ever since. However, through experience from my degree and general interest I have come to understand it at a fairly good level.

So if you know about HDR and I have said something wrong or anything like that then tell me what I have said wrong and ill change it. As there is a strong chance I may get some of the technicalities wrong.

What you need:

You may think you need a £800 ($1500 US) super digital SLR camera with all sorts of advanced features, but to do a half decent HDR, you really don't. Although all of the functions on a SLR will definitely help you gain that extra 30% advantage in quality, such as fast capture speeds and the ability to write images to the RAW digital image format. Generally SLR HDRs will be better, but I get by with a standard "point and shoot camera".

You can get by with the following:

* A digital camera that can take images at different exposures (not brightness), even better with an "Auto Bracket" function.
* Adobe Photoshop CS2 or greater and/or Photomatix.
* A tripod, monopod or a very steady hand.
* To have at least a basic understanding of Adobe Photoshop or editing images with a similar image editor.
* A tripod, monopod or a very steady hand.
* A fairly big storage card, you are most likely going to take a lot of photos, (I regularly fill up my 1GB storage card with photos after a long photo session).

My Setup

I have managed to scrape through with a Panasonic Lumix DMC-FX9 6MP digital camera. It cost me £150 ($296 US) on sale from £200 ($395 US) from a local camera shop, so it's nothing more than a slightly above average "point and shoot" digital camera.
I use a monopod sometimes for long exposures or large exposure sets (3+), a monopod is a pole with a camera mounting screw in the top, like a tripod with one leg. I got it for Christmas one year, as it doubles up as a walking pole as I'm into mountain walking etc.
I use Adobe Photoshop CS3 and Photomatix software for merging exposures and post-production stuff.

What is HDR?

Wiki page:
HERE

High Dynamic Range or HDR (also known as HDRI where the I is Image/Imaging), is a method of storing images digitally which stores a much higher colour range than usual. It means you can capture an image and really make it shine.

If you have ever been on top of a mountain on a sunny day and seen an amazing view or seen an awesome sunset on a beach and thought, wow, that's amazing and then taken a photo. You will know that unless you are a decent photographer, it just doesn't even look a quarter as good as it did when you saw it. This is because the colour range in digital cameras (and to a lesser extent, film cameras) is limited, as what the human eye can see and what the camera can see are very different.

The camera only captured a small range of the colours on offer in that scene. With HDR, you capture a much larger colour range by taking the same picture several times at different lighting levels (exposure) and then merging them together into 1 HDR super picture.

You cannot fully view a raw HDR on a conventional monitor, like 99% of image formats the CRT and Flat screen monitors too can only display a limited range of colours. Though up market flat screens I think can display slightly more, when you are viewing a raw HDR on your computer you are really only seeing a small part of its complete colour range.

With methods in Photoshop and Photomatix, to make a HDR for viewing on the web etc, you compress parts of the HDR colour range in order to enhance details in both the light and in the shadows using various techniques.

How it works (you can skip this bit if you want)
Images stored as JPEGs on a computer are made up of 3 component colours, Red, Green and Blue (RGB) and each colour is stored as 3 numbers from 0-255 representing the mix of RGB required to get that colour. Meaning JPEG can choose from 255^3 colours, which is 16,581,375 colours. Now that may sound like a heck of a lot, and it is, but the human eye can see far more colours than this, into the billions I think.

JPEG is an 8-bit image format, which means it stores RGB values in the range of 0-255 (2^8 = 256). High quality image formats such as TIFF and TGA can store images in the 16-bit colour range, meaning they can store colours in a mid HDR colour range. However, HDR images store colours in a 32-bit colour range or even more. Meaning they have a fantastic amount of colours (I don't believe my calculator, but I think (2^32)^3 is the right answer).

Making a HDR

Take the pictures
First off, take your digital camera, and figure out how to take images at different exposures, read the manual, google your camera etc, it varies massively from camera to camera. The exposure is pretty much the amount of light your camera will let into the camera per-picture.

The feature you are most likely looking for is a + or - EV setting, this is the exposure, although this may be called something different on your camera.

Even better is an "Auto-Bracket" feature that will automatically take the same image at multiple exposures in rapid succession at a set range of 1/2 ev or 1 ev between exposures. Mine does 3 pictures separated by up to 1 ev, meaning it takes an image in 0 ev, -1 ev and +1 ev.

user posted image

Once all that is sorted, take some pictures! Remember, that you will need to stand very still, as each image needs to be exactly the same (though Photoshop and to a lesser extent, Photomatix will align them for you), if one of the exposures is blurred then the whole HDR wont work.

Merge to HDR
Once you have some images to play with, upload them to the computer and fire up Photoshop. From the File menu select "[Automate] > [Merge to HDR]". Click browse and select the images that are relevant. Only select the images that are the same and differ only by their exposure, as they will all be layered on top of each other. If it pops up and asks for the fstop settings etc, which it does sometimes, there should be a drop down box somewhere, which lets you set it to EV mode, which is what you want, for this tutorial anyway.

Once you click ok, your computer will probably lag out a bit as it processes each image and aligns them all, this can take anywhere from 5 seconds to 30+ seconds, depending on the number of exposures you selected. You need a minimum of 2, and don't go beyond 9, any more than that and it really doesn't make a difference. The more varied exposures you have, the higher the dynamic range (very dark underexposed and all the way to very light and overexposed).

Eventually it will pop up with a window like below:
user posted image

If its all blurred, then that's because the images were too different, you need to make sure that when you take the picture that you keep very still, especially on the overexposed images where sometimes the shutter will be open for 1 second or more and any movement will be seen in the image, for big exposures, use a tripod, monopod or rest it on a wall or something.

It will probably look washed out or just really crap, that's because the computer is only displaying a small section of the colour range available. We will sort this out later.

It will also sometimes get confused and ask you to fill in the details for the ev settings in the boxes next to the different exposures, as long as these values are approximately right, it should look fine.

When you click ok, it will then make the HDR image, you are then faced back to normal Photoshop mode where you can do anything you want to the image.

Un-Edited Raw HDR

After Effects

You now have 2 choices, tweak it in Photoshop or in Photomatix, there are probably other programs you can use but these are the 2 I shall cover in this tutorial.

If your in a rush, id say Photomatix produces much better results so skip the Photoshop bit below and read the Photomatix bit instead. However you can do some pretty cool stuff in Photoshop though, so it's worth reading.

Photoshop
We now want to collapse the colour range from 32-bit, to a 16 or an 8-bit image. Preferably 8 bit, because if it's going to be saved as a jpeg, it will be 8 bit in the end anyway.

user posted image

Once you select 8-bit or 16-bit then you get a small box appear with sliders in it, it is through this tool you can play with the exposure settings etc, the setting you will most likely need is Local Adaptation, available from the drop down box.

user posted image

Click the little down arrows to show the curve editor.

user posted image

Local adaptation lets you manipulate the levels of light and dark in the image freely, by changing the shape of the curve you can multiply and remove sections of the colour range. By looking at the image's histogram, you can see a graph showing the percentages of black to white in the image. Remember that the black parts of histogram are where there is data stored for the picture, so if you make a big curve that deviates away from the histogram by miles and does not approximately match the general shape of the histogram, you will no longer be manipulating the image's data, but data that Photoshop is making up for you which means it wont look all that great. Then again if you aren't after realism, have a play around, see what you can do, you can make some really interesting effects.

user posted image
user posted image

Once you click ok, you are now back to normal Photoshop mode, you have collapsed the colour range and now what you see, is what you get, so you can now save as a jpeg or Photoshop in George Bush, whatever. Your done.

Alternately... You can use Photomatix....

Photomatix

Ok, roll back to when you had just merged the HDR in Photoshop, you haven't touched it other than you just merged the exposures.

Get the Photomatix demo here:
http://www.hdrsoft.c...wnload.html#pmp


I use the Photomatix pro demo, fortunately it isn't one of those really annoying demos, which times out, has a limited number of executions. Instead it discretely puts "Photomatix" into the image somewhere; sometimes it's in the middle, sometimes not. However I get around this by taking a screenshot of the preview that it gives you for Tone Mapping.

Tone mapping in Photomatix is really powerful, it gives you loads of control over how the final image will look, and is generaly spot on when it comes to getting the most out of a HDR.

Go to "[File] > [Save As]" and then save it as a Radiance Image (*.hdr). Now open it in Photomatix, and select "[HDR] > [Tone Mapping]" and you are given a screen like below.

user posted image

Strength: The level to which the Tone mapping will be applied, i usualy set it on 100%.
Colour Saturation: How adjust to how bold and vibrant you want the colours will be.
Light Smoothing: This one is fairly important, it sets how much influence light areas have over their surroundings.
Luminosity: Sort of like a brightness and contrast mix, except it varies according to light and dark, makes light things stand out more.
Micro Contrast: How much the fine details will stand out.
Micro Smoothing: Doesnt seem to have a huge effect, similar to micro contrast, it blurs fine details more.
White Clip: Remove up to 5% of the white end of the colour range. Similar to Contrast.
Black Clip: Remove up to 5% of the black end of the colour range. Similar to Contrast.
Gamma: Not sure how to discribe this, it behaves in a similar way to luminosity.

When you are done, you can set the preview size to 1024 (radio buttons at the bottom) and then screenshot the preview, or you can click OK and it will process the entire HDR to those settings and you will have to put up with "Photomatix" being in your image. Unless of course you buy it.

Paste the screenshot into Photoshop and then crop, add borders, adjust, whatever, save as a jpeg and then your done.

This may seem to take ages but you get pretty quick at it after a while.

Tips

* Use a tripod or something to keep the camera steady, nothing more annoying than getting home and finding 1/2 your HDRs wont merge because you couldnt keep the camera steady.

* Try merging them in Photomatix first, if they are blurry then merge in Photoshop, as it does a much better job of matching exposures.

* Set your camera's exposure first, then turn on autobracketing and take the shot, and then move the exposure up and do the same, saves alot of time and you get a massive exposure range. So first set it to -1 ev turn on autobracketing, take the shot, then set it to 0 ev take it again and then set it to +1 ev and take it again and you should end up with 9 exposures.

* Try macro (ultra close up) HDRs, they look pretty awesome.

* Adobe Photoshop CS3 is slow and unstable as its in Beta stages, HDR has been improved on CS3 but try CS2 First, as CS3 is infuriatingly unresponsive sometimes and it EATS memory like nothing else.

* For you 3dsmax users, 32-Bit HDRs make great reflection and environment maps.


Ill add more to this as i think of more...


Hope you found this useful, go and take some pictures and let me know if it worked out smile.gif


Ian Foster 2007, All Rights Reserved.

Yes, my name is Ian wink.gif

ViperGTS-R
  • ViperGTS-R

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#2

Posted 17 May 2007 - 10:37 AM

105 views, has anyone had anybody had a go at this?

dills
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#3

Posted 17 May 2007 - 11:31 PM

I just had a go with my phone camera, pretty pleased with the results, gonna try it outside tomorow, could only do inside my dining room as it's pretty late. If it turns out to be any good then I'll post it either in here or in the photography topic, or both.

Nice tutorial. icon14.gif

vALKYR
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#4

Posted 19 May 2007 - 12:30 PM

Really liked the tutorial, will try it out as soon as I have the time for it smile.gif

Thanks mate!

Mister Pink
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#5

Posted 20 May 2007 - 02:09 PM

Thanks for posting this. Please give me some time and i'll post the results wuth any further questions I'm sure I'll have.

Thanks again wink.gif

ViperGTS-R
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#6

Posted 20 May 2007 - 03:28 PM Edited by ViperGTS-R, 20 May 2007 - 03:38 PM.

Thanks for the comments guys, much appreciated, glad to see your all able to follow it and get results.

It can be a bit long winded, but i think HDR can be really fun, you can take some amazing photos with it. Make mundane stuff suddenly look interesting.

Mister Pink
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#7

Posted 22 May 2007 - 07:10 PM Edited by ThePinkFloydSound, 22 May 2007 - 07:13 PM.

Hey Viper,

I was experimenting with HDR or at least trying. I used an existing photo I had and changed the Levels in the first and merged them. Is this method O.K. or shall take photos with different exposures?

While I was experimenting I came across those nice little effexts you wer talking about.

Before....

user posted image

After....

user posted image

When I have more time I'll try do a serious one. Thanks again Viper for introducing me to this. I've seen one or two shots around. Never understood it or bothered to figure it out. Now I'm glad.

ViperGTS-R
  • ViperGTS-R

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#8

Posted 22 May 2007 - 07:24 PM

What ou are doing is technically not HDR, because the color range you are using isnt real. But yeah you can use this technique to enhance plain photos. Ive done that with a couple of photos. If you force the colour range to 32 and then back to 8 again it gives you the same conversion tools to play with the colour levels.

Allthough all i think you are playing with is the luminosity.

Ill upload a few exposures for people to play with.

ViperGTS-R
  • ViperGTS-R

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#9

Posted 22 May 2007 - 07:51 PM

user posted image

user posted image

user posted image


Theres 3 for now, my internet is slllooowwww today.

EDIT: Whoops, didnt mean to double post, sorry!

Mister Pink
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#10

Posted 23 May 2007 - 11:09 AM Edited by ThePinkFloydSound, 23 May 2007 - 11:27 AM.

I upgraded from Photoshop 7 to CS3 to get the HDR feature so I was happy when I was just messing around with Local Adaption levels and got tht effect.

Thanks for posting the images. I'll try it out now.


Edit: Here's the result...

user posted image






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