# High dynamic range?



## D-50 (Aug 22, 2006)

I was just looking at a post on this site by Andrew Brooks and his use of High Dynamic Range editing. does anyone know anything about this? Can you do it in Photoshop CS? How else can that type of look be achieved?


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## Dom0803 (Aug 22, 2006)

It's quite simple really.

All a HDRI (I- Image) is, is a composition of photographs with different exposures, usually very dark to very light to acheive a perfect blend. All the photos need to be identicle though, and the more exposures you have the better the image will turn out to be.

Read the wiki on it, it shall explain it well. http://en.wikipedia.org/wiki/High_dynamic_range_imaging


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## D-50 (Aug 22, 2006)

I have read about it but when when I look at the resulting photo examples they seem to have that dreamlike quality to them where things somewhat glow. Is that simply a result of the merge or has any other processing been done?  If you look at the images on this site http://www.cambridgeincolour.com/cambridge-gallery.htm especially the one of the bench I would love to know how this look is achieved.


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## Arch (Aug 22, 2006)

we've discussed HDR a few times before...... heres a link to one of them....

http://thephotoforum.com/forum/showthread.php?t=52699

But to answer your other question..... no CS cant do a HDR merge...... but CS2 can, and also Separate programs like photomatix.

Also i didnt see any reference to HDR on the site you linked..... so my guess is he's not using it (also he is an experienced photog/editor)... so he's probably using a combination of other techniques. However HDR could be used to create a shot like the bench one.


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## Dom0803 (Aug 22, 2006)

D-50 said:
			
		

> I have read about it but when when I look at the resulting photo examples they seem to have that dreamlike quality to them where things somewhat glow. Is that simply a result of the merge or has any other processing been done?  If you look at the images on this site http://www.cambridgeincolour.com/cambridge-gallery.htm especially the one of the bench I would love to know how this look is achieved.


I don't see him mentioning HDR anywhere, but they certainly look like HDR's

You have to use programmes with log's in them to have an official? HDR, but I find if I have ten photos with ten different exposures, if I open PS and I use each photo as a layer with an opacity of 10 on each of them, it creates the same effect, and gives an efficient blend.

I guess it's a cheaper method than CS2.

EDIT:

I looked at that guys site, and he definitley uses HDR.

http://www.cambridgeincolour.com/techniques.htm
http://www.cambridgeincolour.com/techniques_dynamic-range.htm


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## Arch (Aug 22, 2006)

Blending 10 photos using opacity is not quite the same as HDR  ...... you dont get a 32bit image.


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## Dom0803 (Aug 22, 2006)

yea but it aint like $600 

Tried out that Photomatrix mentioned earlier. Here's one.. slightly different about it though.. it's a poorly lit room and I'm limited to only two second shutter speeds as my longest, so it wasn't overexposed to begin with, instead correctly exposed.. so it kinda defeats the purpose I guess.


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## benaccent (Aug 30, 2006)

can you post the gerated image on its own so i can see it better? cheers


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## David (Aug 31, 2006)

Here's an image I did some while ago, when I first tested the "Merge to HDR" function of PS CS2. The resolution is reduced for posting:

Click here. (Comprised of seven images from 2 stops below to 2 stops above)

The same image, taken using the auto settings on my Canon 20D, can be seen here

Click here.

Most tutorials I've seen only go through the actual merge to HDR process, however I find that some degree of tweaking afterwards is necessary to get the tones for each colour correct, and to make the image more balanced. I almost always run through the following steps afterwards:

1. Duplicate the window and convert to lab, then select the lightness channel on the duplicate.
2. Redistribute contrast with the Shadow/Highlight tool and stretch it into the midtones further. Keep an eye on the histogram before and after this step.
3. Perform a curves adjustment on just the shadows so we can deepen them a bit without losing detail in the overhead light fixtures.
4. Sharpen as required using smart sharpen or using a mask to highlight the edges of the image.

(Thanks to Kevin F for his help with this.)

Doing this to the above image produces this:

Click here.

I actually think I went a bit too far with the darkening of the shadows in this one, but the principle is sound. I also haven't gone into detail about the adjustments in the steps above, so if anyone wants me to, or would like some screenshots then PM me.

Out of curiosity I tried using the merge to HDR function on some random images, one of which was the photo used above. You can get some interesting effects, but you need to choose your images carefully (using the exif data) to ensure that you have the necessary tonal range for the HDR process or PS CS2 will not allow you to continue with the merge. The result I got from this is here.

I love HDR images, and have always rated the Cambridge in Colour site as one of my favourites. His techniques are excellent as are the images.

Posted in case the above ramblings help with anyone's HDR process flow. IMO time consuming, but very worth while results, especially night scapes involving lighting.

David.


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## Digital Matt (Aug 31, 2006)

I just want to clarify something, since it seems to me that people are getting the wrong idea bout HDR.

HDR is not a new thing.  It's not a digltal-only thing.  It's not software based.

It simply means, capturing a higher dynamic range than the normal contrast range of the medium.  It can be done with film, or digital, and has been done for many many years, long before photoshop and the "Merge to HDR" function.

It doesn't require photoshop, or 8 exposures.  It can be done with split and graduated neutral density filters.  It's just a way to deal with a scene that has very bright highlights, and very dark shadows, much the way that the zone system helps to control this.  For landscapes involving a bright sky, and a dark foreground, nothing more than a graduated neutral density filter, and one good exposure, are needed for an image that covers the entire "high" dynamic range.  Understanding that will help you understand what you are doing with software, and what to do in the field, before you attempt it in post.


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## markc (Aug 31, 2006)

One of the problems I have with some of the "HDR" image I see is the contast is rather goofed up along with continuity of tones. You can't just take the well exposed area of one image and plunk it into the blown out area of another image. There needs to be a smooth constant ramp from dark to light. If you have a spot of 50% grey in one image, and a spot of 50% grey in another image, they should not be the same shade in the combined image. They may looks like the same tone, but because they were exposed differently, they are different in the "real" world. When combined, one should be lighter than the other. That's why the layer method doen't work in my opinion.


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## Digital Matt (Aug 31, 2006)

markc said:
			
		

> One of the problems I have with some of the "HDR" image I see is the contast is rather goofed up along with continuity of tones. You can't just take the well exposed area of one image and plunk it into the blown out area of another image. There needs to be a smooth constant ramp from dark to light. If you have a spot of 50% grey in one image, and a spot of 50% grey in another image, they should not be the same shade in the combined image. They may looks like the same tone, but because they were exposed differently, they are different in the "real" world. When combined, one should be lighter than the other. That's why the layer method doen't work in my opinion.



I agree Mark.  The majority of images I see that are done with this newfound HDR method look really wrong to me.  Completely unnatural.


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## PNA (Aug 31, 2006)

Digital Matt said:
			
		

> I agree Mark. The majority of images I see that are done with this newfound HDR method look really wrong to me. Completely unnatural.


 
I just tried a 7 photo sequence using PScs2 and it was poor......I would have rather taken a bracket of shots and worked them over in PS.


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## Arch (Aug 31, 2006)

It really depends what you use it for...... some HDR's i have seen are flat.... and I usually say so if they are.... if i create one myself and i dont like the results, i bin it.....this happens alot with landscape HDR's because instead of the light having a natural effect on the scene, the light is kind of forced, so it has equal distribution. So it should not be used just because it _can_ be. Having said this i have seen some amazing landsapes which used the merge to HDR command.

But HDR can have a great effect for scenes which have a harsh seperation of light from dark..... as in the kind of scene often mentioned with HDR.... 'the inside of a church'..... where you have coloured glass..... ornamental carvings in the shadows etc.... and you want to show it all.

This _can_ be achived using a zone system.... but unless you have the time and skill to 'paint' back in certain areas.... and give those areas thier own adjustment layers etc..... HRD offers a quicker and improved method.

The term 'high dynamic range' is nothing new..... but the ability for a computer to automatically merge pictures and create 32bits of colour and light information to play with, is. 

oh, and reflections are another bonus of HDR..... check out the helicopter above that David posted... a good example of how the merge to HDR command can be effective.


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## markc (Aug 31, 2006)

I also think that for a shot to be truly useful for constructing an HDR image, it should have a true white and black point. Very dark and very bright images don't help.

I'll try to illustrate what I'm thinking:

You have a wall that goes from very dark to very light. Your film/sensor can't expose the whole wall correctly, so you take 3 images (for example).






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None of them expose the whole wall correctly on the own, but with these 3 images we have the wall covered. Any more images won't really help in this case.

If you just use the right side of the left image and paste it into the right image, you kill the contrast, but if you combine the tonal curve, you get this:






But yeah, there are some amazing HDR images out there. The good ones are really, really good.


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## PNA (Aug 31, 2006)

markc said:
			
		

> But yeah, there are some amazing HDR images out there. The good ones are really, really good.


 

How can you tell those from any others??? I understand your example......

No doubt my technical skills are limited and just pushing buttons is not the answer to finely tuning a photo.


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## markc (Aug 31, 2006)

acsonpg said:
			
		

> How can you tell those from any others??? I understand your example......



Do you mean from the HDR images I don't care for or normal images?

The good HDR images have a full tonal range and good contrast, and while they can look rather etheral, you won't find areas that should be lighter than another actually looking darker. Those are the kind of things you don't always notice right off the bat, but the brain still picks up on them and says "wrong!" Like if a shadow area under a bridge has the same darkness as a tree's shadow. The bridge shadow should be darker.

Telling a good HDR image from a regular image is more about being familar with the dynamic range of film and sensors. If you see a wide exposure range in an image, it's probably HDR. But the wider the range, the more "blocked up" it will be also, since the step between each color becomes larger. A 3 ev range across 256 levels is .01 ev per level. A 10 ev range across those 8 bits is .04 ev per level. You can end up losing fine detail as it all becomes one color, since you are compressing 10 ev to fit in the same space as 3 ev.


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## ksmattfish (Aug 31, 2006)

"Merge to HDR" is a technique that takes 3 or more different exposures of the same scene, and uses them to create a 32 bit image file with a higher dynamic range than would be possible in a single exposure with the gear/media/materials.  For DSLRs with a normal dynamic range of 6 stops or so it's possible to get a file with a dynamic range of 10 to 12 stops with 3 exposures bracketed at 2 stops apart.  

This 32 bit file with the higher than normal dynamic range is not really viewable on most monitors or any print, because monitors and prints have a maximum displayable dynamic range of about 5 stops.  To create an image that is printable, or viewable on a normal monitor, the 32 bit file is converted to a 16 or 8 bit image file, and the dynamic range/contrast is compressed using a variety of methods depending on your software.  

The part of this that most people notice actually has little to do with high dynamic range.  It's the appearance or manipulation of the *local contrast* that makes it look the way it does.  It's completely possible to manipulate the heck out of the local contrast in a regular dynamic range photo, and get similar looking results.  Burning and dodging, adjusting lighting ratios, the zone system, graduated ND filters, USM (in the darkroom or PS), contrast masking, tone mapping, and the various methods of converting from 32 bit HDR files are all techniques for manipulating local contrast.

BW film has a higher potential dynamic range than most other photographic media, but getting 10 to 12 stops on a BW neg is still within the normal range for a single exposure.  Merge to HDR with 3+ different exposures should allow for dynamic range beyond what is possible in a single exposure.  Not that we can see it all at once with current technology.

I think people like it because the photos with heavy local contrast manipulation look like paintings (ala Photomatix).  Painters have been using local contrast manipulation for centuries.  But just like any technique, it doesn't have to be taken that far.  Local contrast can be manipulated to bring out more details in the shadows and highlights, and still look like a "normal" photograph to the viewer.


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## ksmattfish (Sep 1, 2006)

One thing that maybe should be pointed out.  I'd say that in both examples above (the helicopter and the glass vase) the contrast range in the scenes don't appear to be beyond what is normally capturable with a DSLR.  In any scene with a "normal" dynamic range there are numerous ways to lower contrast, open up the shadows, lower the highlights, etc..., although if you like using merge to HDR that's fine too.

To really see what merge to HDR can do find a scene that's blowing past both ends of the histogram.  Like a dark interior room with windows open to a bright sunny day.  Look for a shot that's impossible to get anything decent in a single exposure.  That's when merge to HDR really shines.


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## Arch (Sep 1, 2006)

The amount of of reflection detail and 'shine' to the helicopter seems beyond the capabilities of a single capture too tho


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## PNA (Sep 1, 2006)

"OVERLOAD"!!!!!

I just learning to open PS......


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