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HDR Imaging FAQ

Golden Gate in HDR

Photo by vgm8383

HDRYou need to get few things clear before you shoot.

After writing about HDR Image Creation Techniques & Top 10 HDRI Tutorials, this article answers the questions that are frequently asked about HDRI.

Why does the HDR image look so dark?

The ratio of the dynamic range of HDR image is higher than the display resolution properties of a regular monitor. That is why, a HDR image’s ratio is of highest intensity value, whereas a monitor screen can display only ratio up to 100:1 to 400:1 (TFT) in a natural way. Therefore, to make the image fit to the monitor and look presentable, it need to be tone mapped. And, hence it looks dark.

Does one always need an HDR?

No, High Dynamic Range or even Medium Dynamic Range can also be used in a high contrast lighting situation. This is obviously not always the case, for instance a foggy morning on an overcast day, where one has to shoot in a low contrast lighting situation, then there is a very little need for an HDR file.

What are MDRs, LDRs and SDRs?

These are abbreviations for Medium Dynamic Range, Low Dynamic Range and Standard Dynamic Range. They all refer to an average scene that you might shoot in normal fashion, i.e. non-HDR.

Which is a better setting to use — Wider or Longer focal length?

Actually, both the settings have drawbacks to them. But it depends on one’s need of what is been clicked. Wide shots are faster, save faster, resulting in requirement of fewer images to re-touch. But the downside to it is in getting a final image out of 6 images, with lesser resolution. Plus, the wide lenses have more chromatic aberration which is not a problem, but one nevertheless should be aware about the same. For giga-pixel panoramas, one needs longer focal length lenses and extra stock of memory card and a larger hard drive space.

Does one need to buy an expensive, professional light meter or colorimeter?

For professional photography and correct exposure of the image many digital SLRs cameras now are present in the market with LCD to review it. Even cameras have option of histogram to view darkness and lightness of the image which are accurate as during daylight its difficult to figure out exposure range of the image on the LCD. Thus, expensive, professional instruments are necessary to master the trade.

Why does the Preview sometimes show a regular pixel pattern?

This pixel pattern becomes visible in LDR Mapping mode Compressor. The compression algorithm causes this as the result of tone mapping, which depends on resolution and the visible field of view. Thus, Navigator and Preview give different results. The pixel pattern shows Navigator pixels within the Preview. This way, the pattern reveals intensity differences between Navigator and Preview.

Can one save the tone-mapped result in JPEG format?

It is not advisable to save tone-mapped image as jpeg format. FDR Tools is not a full-fledged editing application, as they only allow the user to merge and tone map the image in real time. In the FDR Tools, things like sharpening, retouching, resizing, etc are not done by saving the image after tone-mapping in jpeg format might result in less resolution and clarity of the image. So, its safer to save it in format like TIFF.