Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Reply
 
Thread Tools Search this Thread
Old Jun 3, 2010, 3:17 AM   #1
Senior Member
 
MartinSykes's Avatar
 
Join Date: Feb 2010
Location: Cheshire, UK
Posts: 854
Default Image size vs. quality

Quick question - I'm looking at the FZ35. It has a 12.1 Megapixel, 1/2.33 sensor. It can record different image sizes like any camera.

Multiplying 12.1 by the relative sizes of a 1/2.33 and a 1/1.7 sensor gives about 7. So, If the FZ35 is set to record approximately 7MP images would it give results similar to a 7MP camera with an actual 1.7 sensor?

Or does the image scaling work differently to that?

[EDIT - This maths is wrong as explained below]
__________________
AutoHDR - Free HDR software for Windows at http://www.autohdr.co.uk on Facebook at http://www.facebook.com/home.php?sk=...36045126467361
My Flickr stream: http://www.flickr.com/photos/martinsykes
Panasonic DMC-FZ38, Sony ­α580

Last edited by MartinSykes; Jun 3, 2010 at 5:52 PM.
MartinSykes is offline   Reply With Quote
Sponsored Links
Old Jun 3, 2010, 7:30 AM   #2
Senior Member
 
Ordo's Avatar
 
Join Date: Jul 2009
Location: BsAs
Posts: 3,452
Default

Not sure about that math. You have to consider not just pixels number but also pixel density, pixel size, increased noise, etc. A 1.7 crop sensor is a different species.
Ordo is offline   Reply With Quote
Old Jun 3, 2010, 4:54 PM   #3
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

The logic behind your math escapes me. Perhaps you've overlooked the fact that 1/2.33 image sensors are smaller than 1/1.7 image sensors. A 1/2.33 image sensor is about 6.4mm x 4.8mm, while a 1/1.7 image sensor is about 7.6mm x 5.7mm. A 12MP image sensor has a resolution of about 4,000 x 3,000 pixels. On a 1/2.33 image sensor, that would be about 625 pixels per millimeter. If you scale that resolution to the size of a 1/1.7 image sensor that would be 526 pixels per millimeter, and at a size of 7.6mm x 5.7mm, that would be 4000 x 3000 or a 12MP image sensor.

What are you trying to do?
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Jun 3, 2010, 5:51 PM   #4
Senior Member
 
MartinSykes's Avatar
 
Join Date: Feb 2010
Location: Cheshire, UK
Posts: 854
Default

My maths was backwards.

My assumption is that the IQ given by a sensor depends on the size of the individual pixel elements.

The sensor size was a bit of a red herring but multiplying 12MP by the area of a 1/1.7" sensor and dividing by the area of a 1/2.33" sensor gives about 17MP. So, I would assume a 12MP 1/2.33" sensor should have the same IQ as a 17MP 1/1.7" sensor as they would both have pixel elements of about the same size.

Anyway, I suppose my real question is whether the IQ delivered by any given camera improves significantly if you take lower resolution pictures with it.
__________________
AutoHDR - Free HDR software for Windows at http://www.autohdr.co.uk on Facebook at http://www.facebook.com/home.php?sk=...36045126467361
My Flickr stream: http://www.flickr.com/photos/martinsykes
Panasonic DMC-FZ38, Sony ­α580
MartinSykes is offline   Reply With Quote
Old Jun 3, 2010, 7:34 PM   #5
Senior Member
 
Ordo's Avatar
 
Join Date: Jul 2009
Location: BsAs
Posts: 3,452
Default

In my own experience IQ is reduced. I recall trying 7Mp in my 10Mp camera and the images were not comparable. There must be some kind of algorythm going there as the lens and the sensor are the same. Just guessing.
Ordo is offline   Reply With Quote
Old Jun 3, 2010, 8:18 PM   #6
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

Quote:
Originally Posted by MartinSykes View Post
... Anyway, I suppose my real question is whether the IQ delivered by any given camera improves significantly if you take lower resolution pictures with it.
No. In fact, it decreases significatly. That's why a resized photo is no use in showing camera quality.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Jun 3, 2010, 8:37 PM   #7
Senior Member
 
VTphotog's Avatar
 
Join Date: Mar 2005
Location: Extreme Northeastern Vermont, USA
Posts: 4,214
Default

Pixel size (or pixel density) has more effect on noise and sensitivity than on IQ. IMO, the biggest reason that larger sensor cameras have better IQ, is the Blowup Factor (my term for what is basically the inverse of Crop Factor). The more you magnify an image, the more visible the imperfections become. If you start with a sensor with a Crop factor of 6, you have to magnify 6 times more than from a 35mm full frame sensor, for the same size printed image. Noise, edge blurriness, etc, become much more of a factor in the print. Of course, this is predicated on all other things being equal, which of course, the aren't.

brian
VTphotog is offline   Reply With Quote
Old Jun 8, 2010, 3:31 PM   #8
Senior Member
 
Join Date: Aug 2009
Location: Dundee, Scotland, UK
Posts: 106
Default

I have to say that I was most unimpressed with the IQ of the Lumix FZ38, but I was comparing it to my Nikon D90 from last year which is obviously not a fair comparison - after all, superzooms are just exalted compacts, whereas "enthusiast" DSLRs are potentially very high performance cameras when mated with quality glass. It's definitely worth spending just a little extra to get a cheap/entry level dSLR as the picture quality improves drastically, even though the zoom functionality of the camera is compromised.
__________________
1DsII | 5D | 17-40L | Sigma 50 1.4 | Sigma 105 2.8 Macro | 70-200 2.8L IS
Davi is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:07 PM.