Artificial brightness adding noise (photomatix)

[TheStupidForeigner]

I'm using Photomatix but I notice when I make a HDR image it artificially increases the exposure on areas that it thinks are too dark and of course this causes a lot of noise. What is the best way to adjust this and produce less noise on my images?

 

[TheNevadanStig]

When merging the photos, it should have a box to check that reads something like "reduce noise on underexposed images". You can also do it in another post program after photomatix.

 

[SCraig]

That IS what HDR does. HDR means High Dynamic Range and it is doing what it was designed to do, it's trying to increase the dynamic range of the image. If you are only using one image then it isn't "Causing" noise it's only emphasizing what was already there.

The normal HDR method is to combine multiple images, usually one that was exposed for the shadows, one that was exposed for the mid-tones, and one that was exposed for the highlights. This allows the software to combine the three (or more) to bring out detail in the shadows and highlights while retaining the mid-tone detail.

 

[TheStupidForeigner]

That IS what HDR does. HDR means High Dynamic Range and it is doing what it was designed to do, it's trying to increase the dynamic range of the image. If you are only using one image then it isn't "Causing" noise it's only emphasizing what was already there.

The normal HDR method is to combine multiple images, usually one that was exposed for the shadows, one that was exposed for the mid-tones, and one that was exposed for the highlights. This allows the software to combine the three (or more) to bring out detail in the shadows and highlights while retaining the mid-tone detail.

I know but I don't want it to make anything brighter than it is in the brightest image. For example I took some photos in a salt cave but it tried to make it exposed to the same brightness of an outdoor scene. And the amount of noise it adds is sooo much...

so I'm asking, are there any methods of reducing it? I of course use noise reduction on underexposed images and reduce more in lightroom later but I'd like to prevent it rather than reduce it later.

 

[Scatterbrained]

You do know there are a multitude of presets in Photomatix right? Not all of them are so aggressive. Personally, I have switched to using the Photomatix "Merge to 32-Bit Tiff" plug-in for Lr. Merge all of your images into a 32bit floating point Tiff file and then edit it in Lr as if it were a fresh raw file, then send it to Ps for a bit more work. Before that plug-in I tended to stick to the "Auto" or "Neutral" settings. The trick is to try and get a flat image from Photomatix that you can work in post, rather than trying to get a finished image in Photomatix. Photomatix isn't nearly as good an editor as Lr or Ps.

 

[TheNevadanStig]

Don't use a high ISO either and it will be fine. Adjust the exposure levels using shutter speed, not ISO.

 

[SCraig]

I know but I don't want it to make anything brighter than it is in the brightest image. For example I took some photos in a salt cave but it tried to make it exposed to the same brightness of an outdoor scene. And the amount of noise it adds is sooo much...

so I'm asking, are there any methods of reducing it? I of course use noise reduction on underexposed images and reduce more in lightroom later but I'd like to prevent it rather than reduce it later.

Something like photos in a salt cave would certainly be a perfect use for HDR software.

Are you using multiple images as opposed to trying to tone map a single image? The bottom line is really that the software isn't creating the noise, the settings on the camera are, and you're going to have to control it when you take the shot.

I just use the "Essentials" version of Photomatix, but even it has some controls that allow me to adjust brightness and the blending point so you should be able to find a happy medium there.

Sorry, I don't do a lot of HDR so I don't have a simple answer to your question other than to prevent the noise from getting in the images in the first place. To that end I'd also mention that there are times when shots on either the high end or the low end of the dynamic range aren't needed and one can focus on one end of the exposure. Using your salt cave as an example, odds are good that pulling detail from the highlights isn't going to be a problem so I would probably take several shots on the dark side of the proper exposure, and maybe only one on the highlight side. That will provide a lot more latitude on the dark side for helping to control the noise.

Noise is ALWAYS going to be more prevalent in dark areas than it is in light areas. Take a look at This Article and think of it in terms of getting detail from the shadows using HDR. It may give you some insight on what's going on and some ideas on how to avoid the issue.