Friday, November 16, 2007

HDR Tone Mapping Using Film Profiles

By definition, an HDR image contains more latitude in pixel brightness than can be displayed on a monitor. When you take a standard digital photo of something bright like the sky at sunrise, a short exposure may capture the sky properly, but the ground will be black. Re-expose to capture the ground and now the sky is blown out.


The really maddening thing about digital cameras if that you get to see the photo right after you take it. So you see your black ground on the screen but then look up to find that the ground isn't black at all. In fact, it may look about as bright to you as the much lighter exposure where the sky is completely gone. There you stand with your eyes easily able to see everything, a little annoyed with your camera's poor showing.

In a nutshell, the problem is dynamic range. You eyes can capture a wide dynamic range, but the camera is capturing a narrow one. HDR photography lets you combine different exposures to create a floating point image that represents the real world scene being photographed, sans your camera's limitations. But then when you want to show these scene-referred pixels on your monitor, you have to do some tone mapping.

Here are examples of tone mapping available in Adobe Photoshop and After Effects. The first four are the standard ones that ship with Photoshop, while the last two are made using a technique I'll show you.


Legend:
1. sRGB / Gamma 2.2 curve
2. Highlight Compression
3. Equalize Histogram
4. Local Adaptation
5. Film Profile Tone Mapping
6. Film Profiles + color correction and film grain

The sRGB curve in #1 is what is typically displayed by default. A gamma curve is applied to the 0.0-1.0 range and the rest is clipped. This is what you'd get from just taking a regular photo.

Options 2-4 try to bring bright values down into visible range without crunching the other pixels too badly. You can see in each example that more detail has been brought out around the sun and the coarse clipping has been reduced. However, each technique has trade-offs. You'll notice that detail is lost in areas where a bright object comes close to a darker one such as the disappearance of a clear horizon line near the sun. Local Adaptation can sometimes produce halos in these circumstances as it fights to maintain contrast while bringing pixel values together. Sometimes the image comes out looking more like a painting than a photo.

Don't get me wrong, each image is different and these algorithms can produce some good results. But a tone mapping technique I have grown to like involves simulating the way film would capture that same scene. For one reason or another, people have always had a fondness for the look of film, and many movies are still shot on film for this reason. But what is it about the look of film that people like so much?

One explanation is that film is the original high dynamic range capture format. Even under long exposures a film negative is never absolutely 100% exposed, so the bright areas of highlights can retain detail that would be lost by a CCD.

After Effects CS3 ships with a series of ICC profiles that describe the response of different film stocks to light. Since an HDR image describes the actual light in a scene, converting from the linear HDR color space profile to a film stock profile using the Color Profile Converter creates a simulated negative in Log space (make sure you use the Absolute Colorimetric intent). From there, you can apply a Theatre Preview Profile, which simulates that negative getting printed on a film positive and the projected. So if you trust the color science involved, you're looking at your scene as if you had shot it for a Hollywood movie.


Looking at example #5, you can see that the results are pretty impressive. There is a good tradeoff between detail around the sun and detail in the rest of the scene. And the sun has a very nice film-style glow around it with no hard clipping at all. Since the film profile response is a simple curve, you don't get any of the artifacts of the other tone mapping methods. Finally, there is probably something about the simulated printed film that will remind you of all the movies you ever saw before the dawn of the digital age.

In this case I'm doing everything manually—I've disabled all color management by using no working space profile and checking "Preserve RGB" in the HDR files. The same process can be set up as a display LUT so that your project lives in linear, but gets viewed through the film preview. To do so, set a linear project working space, turn on Display Color Management in the View menu, and then turn use View > Simulate Output > Kodak 5218 to Kodak 2383, which uses the same settings I am. However, to actually output an 8-bit JPEG or TIFF with the film look, you'll have to set up the Color Profile Converter as I have.

In example #6, I have done a little more processing. By applying a Levels call to the original linear HDR pixels, I can do a realistic color correction where light is brought down in the scene as it would in nature, making it cooler in this case.

Then I add a little film grain while the pixels are in simulated Log space, in between the two Color Profile Converter applications. Add grain is a 16-bit effect, but this matters little because log space does not need floating point values over 1.0. In fact, Log is usually stored in 10-bit Cineon files, so you have more bits than a typical film scan would.

By switching the simulated film stocks, you can also see how your same scene—accurately stored as an HDR image—would appear using different stocks. Much cheaper than experimenting with the real thing.

14 comments:

Unknown said...

Hi!
Really great idea of tone mapping.
But, maybe I am missing something, if you convert from HDR to film profile why in your example picture in 'to film log' the input profile is set to sRGB. How can sRGB describe actual light in a scene?

Anonymous said...

You will feel good connecting with most of our tutors. 24 * 7 service and support is provided to all our users. We help with projects requiring All Assignment Help work. Get My Homework Done

tom554 said...

Our assignment help service acts as an easy and convenient method to select for experts’ help for completing any academic task within the defined time. So, if you have stress for your assignment, hire our professional writers.

Assignment Help said...

Thanks for the post; We provide excellent writing services to all students who can’t get enough content for composing their academic papers. Through this Assignment Help services, you get wonderful chances to connect with professional assignment writers. Whenever you have stress and tensions, you can’t justify your efforts in the right way. Thus, you must choose the best option to finish your academic papers without any tensions. For that, you have to pick professional academic writers using online assignment help services.

Assignment Help Australia said...

Use Assignment Help to connect with Australian academic writers in just a few minutes. Students can take online assignment writing services in Australia when they have no one to ask their queries and find it tough to write your academic papers.
My Assignment Help
Assignment Help Online
Online Assignment Help

Ojash Yadav said...

En este momento de la digitalización, la técnica habitual para hacer pagos a través del dinero ha envejecido. Sustituya sus viejas técnicas por otras más actuales utilizando las administraciones en línea para pagar directamente a través de sus saldos financieros. Lo valioso de la administración de cuotas versátil que utiliza un pequeño mensaje, que se ha desarrollado obviamente patria desde que surgieron los problemas de ingresos, es que no necesita obtener un teléfono celular, es suficiente tener lo que ellos llaman un "responsable". Los clientes deben seleccionar en la fase de estos bancos, de los cuales indicarán la cantidad y la cantidad de intercambios habilitados siguiendo los parámetros, para utilizar la instalación por SMS. Las personas que utilizan saldos en el Banco de Venezuela banco de venezuela En Linea obtienen y harán compromisos interbancarios. Como un enfoque para obtener ganancias por la función, es urgente estar asociado con el BDV En Linea, en el cual debe iniciar la entrega esencial. Para las personas que tienen un registro gratuito en el banco del tesoro En Linea, puede crear la instalación de SMS de hasta 1,000,000 de bolívares de manera consistente, para eso debe consolidar la función en la instalación telefónica de Tesoro en Tesoro en la web y enviar, retirar la separación bnc , un correo electrónico al 2383 con toda la palabra Pagar, y los principales ejemplos de las cuentas bancarias de objetivos, el número de teléfono del destinatario, el tipo de cliente (V, Correo electrónico o J), el número de tarjeta de personalidad del beneficiario, el número fue con una coma y además dos decimales y código por la tarjeta de clasificación que se elegirá. Banco Bicentenario Debe inscribirse a través de su aplicación banco bicentenario En Linea Payment para explotar el servicio. En ese momento, pagará enviando un SMS al número 7077 juntos utilizando todo el términoEl código QR del video modificado se puede utilizar para descargar videos en su teléfono inteligente. Este convertidor mp3 en línea gratuito permite cambiar sus grabaciones de YouTube a MP3, MP4, MP4 HD, AVI y AVI HD. La interfaz es básica donde simplemente necesita pegar la URL del video y elegir el diseño de rendimiento. El registro modificado se hará accesible en la interfaz para descargar. También está disponible un módulo de programa gratuito para descargar videos. Con este programa en línea, sus grabaciones de YouTube se De hecho, mis abuelos tenían correo electrónico ... durante los años 90.Inevitablemente, el custodio estaba harto de observar involuntariamente que mi correo electrónico llegara al registro de la escuela. Por fin me arrinconó y dijo: "¿Has intentado hotmail ?" Entonces lo miré. Además, en ese primer año, fui un individuo sancionador por el trastorno de correo electrónico gratuito basado en la web. whatsapp web needs no presentation. It is all around the most well known texting application and has the most number of clients., GIFs, recordings, reports, this element bodes well. It tends to be exceptionally dull to return and quest for recently shared media, consequently another propelled search include. whatsapp web beta

online assignment writing help said...

Today, more and more students are going after assignment writing services so as to get assignment writing help and to escape from their writing troubles. Obviously, assignment writing services can help the students to get away from the tensions, strain and worries of writing assignments. Most of the students will be worried and stressed when they get assignments to be written on varied topics and it is definitely a matter of concern because not every assignment service provider has qualified experts and a team that specialises in that particular subject.
top assignment help australia
top assignment writing website
best assignment writing help australia
best online assignment writing help
best assignment writing help

get assignment help online said...

Student can normally have issue finishing Assignments.Many assignments area unit quite difficult and have to be done in a very short period of your time. That’s not continuously possible. After all, there area unit so many assignments from all varieties of subjects that require to be done at the same time. but many students troubled by the deadlines of the Assignment submissions they don't know how to get high-quality assignment in a short time, most of the students get stressed. but now Assignment Help In US is here providing best quality Assignments.
visit here:
online coursework help
online coursework writing
coursework assignment help
online coursework service
coursework help online
coursework writing service
Java Assignment Help
Java Assignment Helper
Java programming help
do my java assignment
coursework help
coursework help service
help with coursework writing

Jenifer Discota said...

Do you have difficulty in writing your engineering assignments? Here is the solution! Choose our mechanical engineering assignment help service and get a high-quality assignment within the given deadline. ABC assignment help has a team of knowledgeable master for writing an assignment.

Unknown said...

http://franziseue8015.ampblogs.com/Cara-Dapat-Bermain-Freerolls-Poker-Terbaik-31484230
http://nationdqs4996.tribunablog.com/how-to-discover-the-bagus-agen-idn-poker-terpercaya-9615659
https://thewaytoplaywinnerr.weebly.com/
http://mounren44913.mybjjblog.com/how-to-find-the-best-poker-indonesia-10254549
http://mounren44913.mybjjblog.com/how-to-find-very-best-judi-bola-10254655
http://franziseue8015.ampblogs.com/How-To-Search-The-Bagus-Judi-Bola-31607889
http://nationdqs4996.tribunablog.com/how-to-find-best-play-situs-judi-bola-9635785
http://biancawqq4321.educationalimpactblog.com/16013408/how-to-find-situs-judi-bola-terbesar

eillajones309 said...

The write up you've got shared with us is extremely fine in quality. If you guys stuck somewhere while writing your assignment and wish assignment help australia.service then contact essay writer.

instant assignment help

abcassignmenthelp said...

ABC Assignment help provides best Machine learning assignment help service through professional computer science experts. You can learn about any area of machine learning like supervised learning, unsupervised learning, predictive models, regression models, clustering etc. from our experienced tutors. Our services come at an affordable cost making it possible for you to score high in assessments related to optimization methods, clustering algorithms, ensemble learning, deep learning, decision tree, gradient boosting or any other area of machine learning.

essay writing service said...

Keep up the glaring job. If you guys unable to attract your professor by the quality of your instant essay and need instant essay help service then hire instant essay writers.
instant essay help
instant essay writer
essay writer singapore
essay help singapore
cheap essay help
best essay help
http://www.arabessay.com/an-essay-on-the-dubai-palm-islands-largest-man-made-island-in-the-world/
http://www.arabessay.com/sheikh-zayed-mosque-abu-dhabi/
http://www.arabessay.com/interesting-facts-about-burj-al-arab/
OMAN
https://sourceessay.com/how-many-pages-is-1000-words/
https://omanessay.com/majan-college/
https://omanessay.com/middle-east-college/
https://omanessay.com/middle-east-college/

crystal said...
This comment has been removed by the author.