ISO

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I have done a little analysis of the EXIF data collected from brave Minolta users who were willing to help me with my project. In this table is what I have found about ISO setting and possible values.
This info is gathered from more than 24.000  pictures but this is still not enough to find all the possible values. See my notes bellow. Comments and your own EXIF data are highly welcomed.

ISO Film Speed Raw P
auto		 A
auto		 S
auto		 M
auto		 A
fixed		 S
fixed		 Note
100 48 x x x x 100 100  
109 49 x x x     100  
118 50 x x x x   100  
129 51 x x x     100  
141 52 x x x        
154 53 x x          
168 54 x x          
183 55 x x     200   MaxAperture
200 56 x x x x 200 200  
218 57           200  
237 58 x           MaxAperture and 4s
259 59           200  
282 60              
308 61              
336 62   x          
366 63 x       400   MaxAperture and UHS
400 64 x x     400 400 MaxAperture and (UHS or 4s)
436 65              
475 66           400  
518 67           400  
565 68              
616 69              
672 70              
733 71         800    
800 72         800 800  
872 73           800  
951 74           800  
1037 75           800  

 

- First of all you can note that there are not only four values of ISO setting as many users expect (100,200,400,800). There are much more finer steps in between. This table show all the values I have found in user-submitted data.

- Next interesting this is that ISO 800 is not the highest possible value. There are (at least) three values higher up to ISO 1037. They will be much more noisy of course.   :-(

- In second column is the value called "Film Speed Raw" this value is written inside MakerNote tag. We can expect that there are ISO setting with raw value equal to 60,61,65,68,69 and 70. They would mean ISO 282, 308, 436, 565, 616, 672 respectively. I have no proof that those values exist today. If you will find a picture with one of missing ISO value please let me know.

- Next three columns show the range of ISO values found when ISO is set to auto in P, A, S and M modes. As you can see the maximum value is ISO 400 so you don't have to worry about camera selecting noisy ISO 800. (S ends by ISO 200 but this is probably caused by lack of test pictures)

- Interesting is that in M mode with auto ISO there is only ISO 100, 118 and 200. ISO 118 and 200 are only in "Portrait Mode". So do not underestimate Digital Subject Programs they can do things which you cannot do manually.

- Next two columns are very interesting. They show you that you can set ISO to fixed value but still the camera can choose different ISO value (although in limited range). It seems that in A mode the camera is allowed to go one step below. So instead of ISO 200 you will get ISO 183. This usually does not matter as the resulting picture is therefore less noisy. But you should be really aware in case of S mode. In this mode the choice of apertures available to match with selected time is really limited and therefore the camera has to change the ISO value much more. From my test data it seems that the camera is allowed to go three steps higher than is preset. It is fine that the camera can still take a shot with little tweak of ISO but on the other hand it will raise the noise too and this in in many cases not welcomed. So be aware in S mode.

If you have read my short article and found it interesting than ask yourself: "Why I didn't send the EXIF data from my pictures to Dalibor to support his future investigation?"

 

Recommended reading:
- here you can find out disgusting fact that different ISO is NOT achieved by hardware amplifier as was expected but by simple multiplication - Bryan's Forum I hope that someone better in English will write it as an article
- there is a nice article describing Auto ISO feature