The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Real base ISO Phase One

Christopher

Active member
Hi,

Just wanted to clarify before doing my own tests. As there were some graphs posted which show noise development through different ISOs with Phase backs.

Why is there ( or is there actually ) a difference between the 350 and 3100? (100iso vs 50iso)

Is 35on the IQ180 really base or is there no real difference to 50 ?

All the best and thanks for any input.
 

ErikKaffehr

Well-known member
Hi Christopher,

I don't know what graphs you refer to…

DxO used to measure "true" ISO. I think vendors take a lot of liberty with ISO numbers. What is base ISO can be discussed. One way to see it is that it is the ISO that gives best DR. My guess would be around 100 ISO, but that is just a guess.

Increasing full well capacity lowers base ISO, all other factors assumed constant.

Best regards
Erik


Hi,

Just wanted to clarify before doing my own tests. As there were some graphs posted which show noise development through different ISOs with Phase backs.

Why is there ( or is there actually ) a difference between the 350 and 3100? (100iso vs 50iso)

Is 35on the IQ180 really base or is there no real difference to 50 ?

All the best and thanks for any input.
 

vjbelle

Well-known member
Coming from a Leaf/Credo 50 to a Phase 100 I just automatically assumed that 100 iso would be identical and very acceptable. It certainly is. However when shooting the same scene at 50 iso the noise level does decrease slightly. In the real world this would never be seen but at 100% pixels or 200% pixels it is slightly noticeable..... emphasis on 'Slightly'. Really, really splitting hairs here!

Victor
 

bab

Active member
Coming from a Leaf/Credo 50 to a Phase 100 I just automatically assumed that 100 iso would be identical and very acceptable. It certainly is. However when shooting the same scene at 50 iso the noise level does decrease slightly. In the real world this would never be seen but at 100% pixels or 200% pixels it is slightly noticeable..... emphasis on 'Slightly'. Really, really splitting hairs here!

Victor
I would think CMOS has less pixel noise but maybe some electrical noise that 100 Might get hot...hotter than the 50 credo. Running the 100 must have a lot of back end smoke and mirrors to get that puppy to jump huh!
 

Steve Hendrix

Well-known member
Don't you find it interesting that all the cameras and all the lenses, and even all the tripods, across the entire industry, from numerous manufacturers, have nearly identical specification markers?

Cameras - ISO 50-100-200-400-800, etc.

Lenses - 28mm-35mm-50mm-80mm-110mm-120mm-150mm, etc.

Tripod Weight Capacity: 8.8lbs-11.0lbs-17.6lbs-22.0lbs, etc.


How likely is it that the products displaying all these measurements, that are shared by multiple manufacturers, have somehow been independently designed and manufactured and are really exactly as stated? Is it really ISO 50? Or is it 100? Or is it really 74? Oops, can't use 74. The Schneider 35mm APO Digitar XL. Or, err... 36mm.

https://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=1325&IID=1886
Schneider / ALPA Apo-Switar 5.6/36 mm, LB


This goes back to the film days, of course.

With regard to sensors from digital backs, most I've assumed are somewhere between the base and the next stop higher, since you can extract similar noise/dynamic range characteristics. In other words, I've generally treated them the same, unless my testing has shown me otherwise. 2 stops up from base (for CCD), is where I have really started paying attention.


Steve Hendrix/CI
 
Top