16 February 2009

Highlight Tone Priority - ISO range limits

Have you tried Highlight Tone Priority? You know the one, the setting that shifts your dynamic range from the shadows to the highlights giving smoother tonal gradation in the highlight areas. While it's very useful in some situations - anywhere with lots of highlights and not much shadow - it can cause issues when you get to shadow areas as that dynamic range has to come from somewhere - the shadow tones. this could cause more noise in the shadow areas, so use it sparingly. 

Anyway, this post is not about that per se, but about the limitations it puts on your ISO range. We'll show you some examples of images with and without HTP in a future post. 

This list shows you the standard ISO range (with expansion turned on) of the camera and the ISO range once Highlight Tone Priority is turned on. 

EOS-1D Mark III - STD: 50-6400, HTP:ON 200-3200
EOS-1Ds Mark III - STD: 50-3200, HTP:ON 200-1600
EOS 5D Mark II - STD: 50-25,600, HTP:ON 200-6400
EOS 50D - STD: 100-12,600, HTP:ON 200-3200
EOS 40D - STD: 100-3200, HTP:ON 200-1600
EOS 450D - STD: 100-1600, HTP:ON 200-1600

For a quick way to check if you have HTP switched on or not, looked at the information screen - either the top LCD panel for those cameras that have one, or the rear LCD for the EOS 450D. 
On the EOS-1D/1Ds Mark III, EOS 40D and EOS 450D, the ISO speed when HTP is turned on, will show with small zeros eg: 2oo rather than 200. For the EOS 5D Mark II and EOS 50D, this has been changed so that it now shows D+ on the top LCD panel. 


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