H5D - 50. Advantages to rating at 50 ISO?

[Garry Sarre]

I have tried to find the answer from Hasselblad and on the web in general. Does anyone know if there is an advantage to rating the H5D 50 at 50 ISO.... Or is it for shooting blurry water falls ?

[JoeKitchen]

Are you asking if there is an advantage to shooting at 50 ISO, the base ISO of the camera?  Or are you asking whether there was a specific reason Hassy set the base ISO at 50?  

In any event, to answer the first question, 50 ISO is the native ISO of the sensor and would produce the best possible quality to shoot at that ISO.  It would require more light and/or longer shutter speeds, but the main reason to shoot at 50 would be for the best possible image quality. 

For the second, this particular sensor that is in the H5D-50 has a base ISO of 50, unlike a base ISO of 100 for most CMOS sensor based cameras.  That is why the lowest ISO is 50 on this system.  (For CMOS based cameras, they often have a ISO 50 option, however the camera is actually over exposing the image and pulling it down to get that ISO.  This is different.)

[Garry Sarre]

Yes Joe. I was wanting to know if the quality was better at 50... Or if it was, as you mentioned a 'pull' setting for those that require longer shutter speeds or wider apertures for given lighting conditions.

Thank you for your very quick answer.

[torger]

Hasselblad's CCD cameras ISO settings are simpler than most, it's just a value in the EXIF data, the amplification out of the sensor is always the same. That is regardless of your ISO setting you'll be shooting base ISO, just under-exposing more (the raw conversion looks at the ISO value and multiplies raw samples accordingly). Of course you get the least noise if you shoot at ISO50 and have enough shutter speed to make a good exposure.

There are examples in the DSLR world, like a Canon 5Dmk2 when you can shoot at a lower ISO than base ISO, the sensor there is ISO100 but you can shoot at ISO50. It's simply just multiplication in the raw file and you gain nothing in that case. But as far as I know there is no medium format camera on the market where you can shoot lower than the base ISO, in other words the lowest ISO is always the best.

[Garry Sarre]

Yes, your example of the Canon 5D, Mark 1 in my case, was what made me pose the question. I have been thinking that the DR on the HD5 isn't as much as I had hoped at 100 ISO. ie. With my portraits, high lights and shadows are both a little too close to the edges of the histogram. Hopefully 50ISO will give them more room for error.

Thanks for your response Torga.

[BobShaw]

50 ISO gives you another stop bigger of aperture for portraits etc. I wish they would come out with 25.

[Go Go]

Hi Bob,

You can always use an ND filter.

[BobShaw]

You can put an ND on, but that makes the viewfinder darker and detracts from the image quality. Also you need to carry different sizes or step ups which is all much harder than a simple click of a control. Unfortunately big ISO numbers and huge numbers of AF points sell. Handy if you want to shoot a model with 63 eyes at midnight I suppose.