Can someone please help me understand this?

This is taken from an online review site. I mean is the G6 "better" that is more sensitive? Why is this an advantage? Why is there a difference in stated and actual ISO?

TIA

Joe




One thing not to fall foul of when performing this kind of test is the difference between the indicated sensitivity and the actual sensitivity. The actual sensitivity is easily calculated by comparing the exposure used by the camera to that measured by a high quality light meter (ensuring the middle gray patch is equal for all samples and cameras). By doing this we managed to produce the following difference table:


please see tabel here

Interesting.

weird, i just brought that up in a different thread

It's bad, in a way, that canon would deviate from ISO standards, since the point of ISO standards is that they are standard, but it's a FILM standard, not a sensor sensitivity standard, so there's some room for interpretation there I guess. I've read most Canon cameras don't follow the standards, but I'm not sure if that includes film cameras, too.

I'm not sure WHY they'd do it either. My guess is that they came up with four settings, and they figured calling the lowest one "50" sounded better to the marketing department than calling it 100 and saying it had less noise than competitors.

But is a "good" thing? How does one interpret this?

right, it's weird. It's not really good or bad, they've basically just fudged the standards, which is generally a bad thing, but with film out of the equation, basically you're getting good photos so does it really matter?

Maybe they way they're looking at it is by the end result of the standards instead of the standards themselves... if their (indicated) 50 gives you the noise you'd expect from (standardized) 100, then why not call that "50" because many amateurs think of ISO as being "hown grainy the film is" rather than "how sensitive the film is"

From what I understand, the ISO (International Standards Org) designed standards (if you're as old as I am, which is only 36, you still call it "ASA" all the time) so that all film and camera manufacturers' products would be comparable. Now that film is out of the equation, ISO is sort of moot, and Canon decided to optimize their settings for the best photos possible, then assign "ISO" numbers to them as a reference to people that understood photography.

I bet in the next few years, sensor sensitivity becomes far more variable and ISO standards will be thrown out entirely. Why have four settings when you could have 12? With ever-increasing noise reduction and metering, why not throw ISO into the mix with aperture and shutter speed to come up with the perfect photo? for that matter, why are cameras still using preset apertures and speeds, couldn't a computer find points within those "notches" that would result in better photos? If 1/60 will overexpose just a hair, why not use 1/65?

But I really don't know much about this stuff, i'm just guessing what Canon was thinking, and writing science fiction. I'm sure Robert Lay will kick in a couple hundred words that will be far better researched than these.

Here is a quote from the conclusion of the reveiw:

"Another interesting point is the conservative approach Canon has taken in labeling its ISO sensitivity, in our tests the G6 proved to have a sensitivity range which was more like ISO 100 - 640 than the labeled ISO 50 - 400, that makes its low noise performance even better."

Still looking for more info.........

G'day!

I think it compares the ISO rating to film rating. You have to think in "reverse" here and forget digital. Imagine low light situation.For example in the rainforest under heavy canopy and you want to shoot a flower at f5.6(greatest clarity for G series lenses in terms of DOF). You don't have a flash, the light is poor and conditions just say use highter iso. You look at your THE ULTIMATE EXPOSURE COMPUTER Don't carry one around? Mine is on 4xA4 pages from Fred Parker site http://www.fredparker.​com/ultexp1.htm Its amazing in its simplicity and follows the good old Sunny16 rule

For argument sake lets take it as EV 7 on his chart. Lets look on the table To shoot EV7 at 5.6 at ISO400 my shutter speed needs to be 1/15sec. A little too low but in some situations and with tripod you can get away with it. Even handheld if you are real steady with your hands. However since Canon "underestimates" its ISO and in reality its close to 640 I would in reality need to shoot anywhere between 1/15-1/30th sec to get my "right" exposure. So 1/15th would give me a overexposed image which would push histogram to the right and expose more shadows. This is a GOOD thing. Remember "SHOOT TO THE RIGHT RULE"? We are deliberatly trying to get the exposure to the far right without clipping any channels. This results in LESS noise in shadows. Of course you will have noise at that ISO. It is unavoidable. However your exposure will be spot on and slightly overexposed rather than underexposed. And for low light situation where high ISO it may need to be used that may not be such a bad thing.

Alternatively you may think well since Canon is conservative I may get away with dropping ISO to 200 (in reality close to 320) and shoot at 1/10th or 1/13th and get less noise in your image. Alternatively keep your ISO400 and bump the speed up to 1/20-1/25th s So here you trying to minimise noise by either using lower ISO or increasing shutter speed

Another way to think of it you are getting ISO640 sensitivity and only paying for ISO400 At lower ISO I doubt one can detect much differences with naked eye on digital photos taken at ISO50 and ISO100 as most in camera processors are extremely effective in reducing/surpressing noise. Hence it is not as essential in lower ISO settings.

I hope it all makes sense to you. The key is forget noise/ISO relationship for a second and think more ISO/exposure. Higher ISO less time is needed to "expose" the film hence better chance of getting away with handheld shots and other advantages.

For my G2 I rarely go over 100 I have taken a few ISO400 by mistake but most of these were not for printing but for memorabilia sake I could use NeatImage and get them silky smooth to a degree but their value to me is more sentimental and noise adds a little character

Regards,
Flagpole

First and foremost film cameras don't have ISO settings. ISO is film rating hence you camera will have ISO setting of the film you load into it

The rest of the post see the post above. The reason Canon brought the ISO rating as is is to stop CONFUSING those people who remember ISO from the point&shoot days. Remember when ISO400 used to mean versatile? So they decided not to mess with well known standarts and just underrate their settings. Its not really trying to deceive anyone but rather designed not to confuse people. They could have equally labeled it ISO100, 200, 400, 800 like SONY has (and overrate their settings) or some other arbitry setting. In reality it makes little difference as all that matters is that the difference is in double steps to allow camera to adjust aperature/shutter accordingly depending on ISO.

If you go to this website http://www.photocritic​.org/articles/ev.php and go through calculations you will see that comperatively it does not matter what values are since when you are going to compare EV=1 (ISO 100) & EV=2(ISO=200) you difference is 1 full stop. And so on. Hence it matters little really what the ISO values are as long as relationship is constat. The difference between ISO50&ISO400 is 3 stops which is the same difference between ISO100&ISO800.

Again you need to stop thinking noise and start thinking EXPOSURE. You can rescue an image which is well exposed and has noise but you can't rescue an image which is noise free and completely underexposed. ISO setting just gives you versatility to grab that "Kodak moment". What you do with it after its up to you

Flagpole

Flagpole wrote:
G'day!

I think it compares the ISO rating to film rating. You have to think in "reverse" here and forget digital. Imagine low light situation.For example in the rainforest under heavy canopy and you want to shoot a flower at f5.6(greatest clarity for G series lenses in terms of DOF). You don't have a flash, the light is poor and conditions just say use highter iso. You look at your THE ULTIMATE EXPOSURE COMPUTER Don't carry one around? Mine is on 4xA4 pages from Fred Parker site http://www.fredparker.​com/ultexp1.htm Its amazing in its simplicity and follows the good old Sunny16 rule

For argument sake lets take it as EV 7 on his chart. Lets look on the table To shoot EV7 at 5.6 at ISO400 my shutter speed needs to be 1/15sec. A little too low but in some situations and with tripod you can get away with it. Even handheld if you are real steady with your hands. However since Canon "underestimates" its ISO and in reality its close to 640 I would in reality need to shoot anywhere between 1/15-1/30th sec to get my "right" exposure. So 1/15th would give me a overexposed image which would push histogram to the right and expose more shadows. This is a GOOD thing. Remember "SHOOT TO THE RIGHT RULE"? We are deliberatly trying to get the exposure to the far right without clipping any channels. This results in LESS noise in shadows. Of course you will have noise at that ISO. It is unavoidable. However your exposure will be spot on and slightly overexposed rather than underexposed. And for low light situation where high ISO it may need to be used that may not be such a bad thing.

Alternatively you may think well since Canon is conservative I may get away with dropping ISO to 200 (in reality close to 320) and shoot at 1/10th or 1/13th and get less noise in your image. Alternatively keep your ISO400 and bump the speed up to 1/20-1/25th s So here you trying to minimise noise by either using lower ISO or increasing shutter speed

Another way to think of it you are getting ISO640 sensitivity and only paying for ISO400 At lower ISO I doubt one can detect much differences with naked eye on digital photos taken at ISO50 and ISO100 as most in camera processors are extremely effective in reducing/surpressing noise. Hence it is not as essential in lower ISO settings.

I hope it all makes sense to you. The key is forget noise/ISO relationship for a second and think more ISO/exposure. Higher ISO less time is needed to "expose" the film hence better chance of getting away with handheld shots and other advantages.

For my G2 I rarely go over 100 I have taken a few ISO400 by mistake but most of these were not for printing but for memorabilia sake I could use NeatImage and get them silky smooth to a degree but their value to me is more sentimental and noise adds a little character

Regards,
Flagpole

Thanks Flagpole that really helps alot.