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View Full Version : ISO values and picture quality



buzz
09-10-2004, 02:58 AM
I have a S1 IS and am looking at the FZ20 because of the 12X optical. The question I have is why does the FZ only go down to ISO 80? The canon goes down to ISO 50. I know that a higher ISO means more light sensitivty. But the images also get more grainy with a higher ISO. I am wondering if the f 2.8 thoughout the focal range forced the issue with the lowest ISO of 80?

Thanks for any info

buzz

John_Reed
09-10-2004, 07:41 AM
I have a S1 IS and am looking at the FZ20 because of the 12X optical. The question I have is why does the FZ only go down to ISO 80? The canon goes down to ISO 50. I know that a higher ISO means more light sensitivty. But the images also get more grainy with a higher ISO. I am wondering if the f 2.8 thoughout the focal range forced the issue with the lowest ISO of 80?

Thanks for any info

buzzHaving seen lots of FZ20 images, and shot a few of them myself on a borrowed camera, I can truthfully say that the images aren't "grainy" at ISO 80. Here's a snapshot I shot at the SF Zoo using the FZ20 at ISO 80:
http://john-reed.smugmug.com/photos/8358039-L.jpg
See any "graininess" there? I don't. I really don't think that the "f2.8 throughout the focal range" has much to do with the sensor sensitivity. I think that Panasonic just made a choice to select a minimum ISO that gave faster shutter speeds in low-light situations, and that they weren't worrying too much about the presence of noise at that ISO level. Beats me why they chose a minimum of 64 for the FZ15; that'll have to remain one of life's unsolved mysteries! But seriously, I tried to use Noise Ninja on an ISO 50 shot from my FZ10 (just to try it out), and it couldn't even find a noise signature to do a profile.

buzz
09-10-2004, 07:46 PM
Nice photo, looks free of any noise to me....

dr150
09-17-2004, 10:35 AM
I read a prof review that the camera has vignetting issues throught the focal range but worse on widescreen end of it.

John_Reed
09-17-2004, 11:13 AM
I read a prof review that the camera has vignetting issues throught the focal range but worse on widescreen end of it.Really? Where did you read that review? I haven't seen one posted anywhere. I've also shot a few shots with the FZ20 and haven't seen much evidence of vignetting. Please identify your source so I can check it out? :confused:

MikeCamp
09-17-2004, 12:04 PM
I read a prof review that the camera has vignetting issues throught the focal range but worse on widescreen end of it.


I'm not buying it.

No vignetting on any of my pics and I've taken alot. I sure would like to read this "Prof" review.

PixChick
09-17-2004, 12:32 PM
I read a prof review that the camera has vignetting issues throught the focal range but worse on widescreen end of it.

Here is the exact quote off the dpreview review, by Simon Joinson:

Macro Focus
The FZ3 has a dedicated macro mode, accessed via the main exposure mode dial - this means you cannot combine macro focus with manual or semi-automatic exposure, which is a pity. The macro mode works throughout the zoom range, but - as is usual on this type of camera - only gets really close when used at the widest setting. There is inevitably some distortion when you get really close - less expected (and less forgivable) is the slight vignetting (darkening of corners). To be fair this is far less visible in real life shots.

Here is the link to the page where it can be found:

http://www.dpreview.com/reviews/panasonicfz3/page5.asp

Notice that it states "To be fair this is far less visible in real life shots"

Also, this was a review of the FZ 3. It is possible that the FZ 20 may not have the issue.

I don't think it is an issue, really. I happen to have just purchased the FZ 20, so I can also say with hands-on knowledge that I didn't see any noticable vingetting. I am sorry not to include any sample photos, but I haven't gotten any onto my web space yet. If you really want zero vignetting, you can always zoom out slightly and crop after the fact.

By the way, that was a very favorable review

PixChick :)

judge9847
09-17-2004, 12:44 PM
To be fair this is far less visible in real life shots.

Err ... am I being dumb here or what? What ISN'T a real life shot???

And by the way, I've NEVER seen any vignetting on any Panasonic images, macro or whatever.

The guy had to be on something or maybe was looking at his results through an eye patch ... :)

PixChick
09-17-2004, 01:05 PM
Err ... am I being dumb here or what? What ISN'T a real life shot???

And by the way, I've NEVER seen any vignetting on any Panasonic images, macro or whatever.

The guy had to be on something or maybe was looking at his results through an eye patch ... :)

Well, I think it means as opposed to the barrel distortion test with certain presets and that weird grid that is photograhed. Who photographs that in real life?? I believe Jeff has made similar comments about issues not showing up in "real world" situations. The bottom line is that this (vignetting) is not an issue. Like I said before, the review was very favorable. His final word on the camera, in the conclusion, was "excellent."

PixChick :)

by the way, I am sure you could post a question about this on dpreview's Panasonic forum and Simon would respond. He seems to be pretty good about that.

Dave Dilks
09-17-2004, 01:09 PM
Err ... am I being dumb here or what? What ISN'T a real life shot???


I think this is the context that brought up the 'real life' comment:

"Vignetting (darkening of the corners of the image) is visible in many wideangle shots - specifically those with large expanses of blue sky and in macro images."

"The vignetting can, of course, be removed using software, and in truth it only really becomes a problem with very close macro shots"

I haven't noticed significant vignetting with my fz3, but I also haven't taken any pictures of large expanse of blue sky or very close macro shots - mainly I try to stick to real life shots. :rolleyes:

D70FAN
09-17-2004, 02:41 PM
I have a S1 IS and am looking at the FZ20 because of the 12X optical. The question I have is why does the FZ only go down to ISO 80? The canon goes down to ISO 50. I know that a higher ISO means more light sensitivty. But the images also get more grainy with a higher ISO. I am wondering if the f 2.8 thoughout the focal range forced the issue with the lowest ISO of 80?

Thanks for any info

buzz

It's generally an arbitrary decision based on the noise threshold approaching zero. The Canon goes down to ISO 50 because that is where they set the "zero" noise threshold. On my D70 minimum is ISO 200. It makes sense that the better the sensor noise immunity characteristic the higher the base ISO setting can be. But again it is somewhat arbitrary, as even most professional dSLR's still offer ISO 100 or even ISO 50 to insure a true zero noise floor.

Bottom line is that it probably doesn't matter.

John_Reed
09-17-2004, 03:19 PM
There is inevitably some distortion when you get really close - less expected (and less forgivable) is the slight vignetting (darkening of corners). To be fair this is far less visible in real life shots.I read this to mean that the FZ3, as he tested it, showed slight vignetting at shortest focal length, i.e., "really close." We don't know exactly how he was testing, but for example if he did so with the lens hood in place, that can cause vignetting at the widest angle settings.

apathetic
09-26-2004, 11:46 AM
Looking at the recently posted pics from the fz20, they appear very noisey, especially in the dark areas. And this is at the lowest ISO setting. Compare that to the 20D samples. Every time I convince myself that I want to buy the FZ20, I see something that shows one of it's flaws. I guess I'll have to wait for the DSLRs to fall into my price range...