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PostPosted: Fri Dec 02, 2011 4:30 pm 
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Joined: Sun Jun 24, 2007 12:20 pm
Posts: 35
Location: Chicago, IL USA
I understand that the higher the megapixel count, the bigger enlargements (or larger crops) you can make and maintain image quality.

Here's my question:
within a given DSLR camera line where two models are essentially identical except for resolution size, is there a difference in quality when similar "quality settings are used between a higher versus lower resolution camera?

For instance
Sony alpha A55: 16 MP
Sonly alpha A77: 24 MP

If you set both cameras to take 8MP photos (so file sizes are similar) would there be any difference in the quality of the photo (assuming you aren't making an enlargement that goes beyond what is appropriate for an 8MP image?

I'm guessing the answer is no difference...


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PostPosted: Sat Dec 03, 2011 2:19 am 
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Joined: Tue Nov 08, 2005 3:32 pm
Posts: 9975
Location: Queenstown, New Zealand
Hi Argelius, it's an interesting question, but be careful with your assumptions.

A higher resolution sensor (that's the same size) will have smaller pixels and therefore reduced sensitivity. This in turn means higher noise levels at the same ISO values, and also reduced tonal dynamic range. So high resolution sensors are a double-edged sword.

But it's important to compare cameras of the same era, as new sensors generally perform better than older ones even if they are higher resolution. The big question is when two sensors are of the same generation.

As for capturing at reduced resolutions, it all depends how the camera scales the image and either throws away unwanted data or combines pixels to improve sensitivity. Sadly no-one provides details on this, so it's a case of comparing for yourself. I rarely have time to test this capability becuase I'm already doing so many tests and most people are only interested in shooting at the maximum resolution.

Something you could try though is downscaling in software. Get hold of images from two cameras and scale them down to the same resolution, and then pixel-peep at 100%. Tell us which looks better!


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PostPosted: Sat Dec 03, 2011 12:24 pm 
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Joined: Sun Jun 24, 2007 12:20 pm
Posts: 35
Location: Chicago, IL USA
Hey Gordon --

Excellent thoughts -- really appreciate your insight here. Ultimately, my real problem isn't the need for more pixels to play with, but a different camera to play with. I'm a gadget-holic and always wanting to upgrade. Alas, the a55 is the favorite camera I've ever had, so I'm content to stick with it. Sounds like uping to the a65 wouldn't be an immense change, so I'll hang out with the a55 a while longer.

Anyway, the point of the post wasn't help in picking a new camera...just trying to understand something, which you expertly handled.

Thanks!


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