ISO Question

Sol Invictus · 10-06-2012, 03:14 PM

I had a general question I was hoping someone could answer.

The K-5 is capable of ISO 80 and my D600 of ISO 50. But in the D600 (and I believe in the K-5 as well) you have to select an option to lower the ISO to those levels. They are part of the expanded range. The base ISO starts at 100 and is expandable to 50, or 80 in the case of the K-5. My question is, if those cameras are capable of these low ISO figures, why are they not enabled by default. Why doesn't the ISO start at 50 or 80? Why is there a need to expand to these levels? Is there an issue with these low ISO figures?

**boriscleto** · 10-06-2012, 03:46 PM

They aren't enabled by default because they are outside the natural range of the sensor. In the past expanded ISO was done mostly in software, on CMOS cameras it is mostly hardware I believe. DxO says the K-5 gets .42 more DR at ISO 80.

Sol Invictus · 10-06-2012, 03:50 PM

Originally posted by boriscleto

They aren't enabled by default because they are outside the natural range of the sensor. In the past expanded ISO was done mostly in software, on CMOS cameras it is mostly hardware I believe. DxO says the K-5 gets .42 more DR at ISO 80.

Thanks. Is there a downside to using these low ISO figures?

elliott · 10-06-2012, 04:01 PM

Originally posted by Sol Invictus

Thanks. Is there a downside to using these low ISO figures?

Think of it like purposely under or overexposing and then pushing it in software later when doing the RAW processing, you'll lose dynamic range.

**boriscleto** · 10-06-2012, 04:01 PM

I haven't seen any on the K-5.

**boriscleto** · 10-06-2012, 04:03 PM

Originally posted by elliott

Think of it like purposely under or overexposing and then pushing it in software later when doing the RAW processing, you'll lose dynamic range.

Then why does DxO say you get more dynamic range at ISO 80? With a CCD sensor that was true, with a CMOS sensor that doesn't seem to be the case except at the upper range. The K-5 loses more DR going from 25600 to 51200 than it gains from going to ISO 80 from ISO 100.

10-06-2012, 03:14 PM	#1
Sol Invictus Veteran Member Join Date: Aug 2011 Location: Calgary, Alberta Photos: Gallery Posts: 392	ISO Question I had a general question I was hoping someone could answer. The K-5 is capable of ISO 80 and my D600 of ISO 50. But in the D600 (and I believe in the K-5 as well) you have to select an option to lower the ISO to those levels. They are part of the expanded range. The base ISO starts at 100 and is expandable to 50, or 80 in the case of the K-5. My question is, if those cameras are capable of these low ISO figures, why are they not enabled by default. Why doesn't the ISO start at 50 or 80? Why is there a need to expand to these levels? Is there an issue with these low ISO figures?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K5: -/+ and ISO button question.	Riv	Pentax K-5 & K-5 II	6	09-10-2012 01:07 PM
K-7 ISO question	varyabol	Troubleshooting and Beginner Help	5	10-17-2011 09:40 PM
Dumb question: how do i set to ISO 100?	nsolarz	Pentax K-5 & K-5 II	2	07-15-2011 06:39 PM
K-x ISO question	mikknu	Troubleshooting and Beginner Help	2	04-08-2011 04:01 PM
Dumb K-5 question re: Auto-ISO	deadwolfbones	Pentax K-5 & K-5 II	18	10-23-2010 10:14 AM

10-06-2012, 03:46 PM	#2
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	They aren't enabled by default because they are outside the natural range of the sensor. In the past expanded ISO was done mostly in software, on CMOS cameras it is mostly hardware I believe. DxO says the K-5 gets .42 more DR at ISO 80.

10-06-2012, 03:50 PM	#3
Sol Invictus Veteran Member Join Date: Aug 2011 Location: Calgary, Alberta Photos: Gallery Posts: 392 Original Poster	Originally posted by boriscleto They aren't enabled by default because they are outside the natural range of the sensor. In the past expanded ISO was done mostly in software, on CMOS cameras it is mostly hardware I believe. DxO says the K-5 gets .42 more DR at ISO 80. Thanks. Is there a downside to using these low ISO figures?

10-06-2012, 04:01 PM	#4
elliott Inactive Account Join Date: Dec 2008 Location: North Carolina Photos: Albums Posts: 1,720	Originally posted by Sol Invictus Thanks. Is there a downside to using these low ISO figures? Think of it like purposely under or overexposing and then pushing it in software later when doing the RAW processing, you'll lose dynamic range.

10-06-2012, 04:03 PM	#6
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by elliott Think of it like purposely under or overexposing and then pushing it in software later when doing the RAW processing, you'll lose dynamic range. Then why does DxO say you get more dynamic range at ISO 80? With a CCD sensor that was true, with a CMOS sensor that doesn't seem to be the case except at the upper range. The K-5 loses more DR going from 25600 to 51200 than it gains from going to ISO 80 from ISO 100.