Digital Image Sensors - is my thinking correct?

[roadtripper]

So I'm definitely going to buy a DSLR over the next six months.

I took some notes as I read more about DSLRs this week and I wanted to make sure that I have these general points down correctly:
(1) The larger the "image sensor" on a DSLR, the less "noise" (aka grain) it will have. This means larger prints with better quality are possible with all other factors equal.
(2) Larger sensors = better in low-light conditions and/or at high ISOs. I'm assuming this means better action and night-time photography
(3) Larger sensors = better dynamic range, meaning improved detail in shadows or other non-highlighted areas.
(4) Larger sensors = better to create blurry backgrounds (i.e. smaller depth of field)
(5) Larger sensors = bring you closer to the actual focal length or focal range of a lens.
(6) Larger sensors = better range of aperture, especially small apertures such as f/19, f/22, etc. (assuming lens is capable of the range).

Any thoughts on any of the above? Are they correct, incorrect and/or largely conditional on other factors? Any other huge benefits of a large sensor that I'm missing?

Probably going with the EOS Rebel XSi unless the Canon EOS-5D Mark II is released over the next six months (it was not released today like many expected - canon announced a new EOS Rebel XS to replace the XTi instead)

Thanks!

 

[kmorgan]

There are some really good articles on The Luminous Landscape . Check out this one for starters and go from there...

Understanding Digital Camera Resolution

Kevin

 

[roadtripper]

There are some really good articles on The Luminous Landscape . Check out this one for starters and go from there...

Understanding Digital Camera Resolution

Kevin

Thanks for the link, Kevin. I read practically every article on dpreview.com and thos were really quite helpful.

 

[DougPaul]

In some cases, the issue is sensor pixel size, not overall sensor size. So, my comments below assume the same number of mega-pixels at the different sensor sizes.

(1) The larger the "image sensor" on a DSLR, the less "noise" (aka grain) it will have. This means larger prints with better quality are possible with all other factors equal.

Less noise: yes at high ISO, not an issue at low ISO
BTW grain is a form of noise found on film emulsions, not digital sensors.
Larger prints: possibly, more due to sharper image on bigger sensor, less because of reduced noise.

(2) Larger sensors = better in low-light conditions and/or at high ISOs. I'm assuming this means better action and night-time photography

Lower noise at high ISO for the same number of megapixels. A larger sensor -> a bigger physical lens aperture (for the same eFL and F-stop), -> more photons per per pixel -> better signal-to-noise ratio

(3) Larger sensors = better dynamic range, meaning improved detail in shadows or other non-highlighted areas.

Generally, but less of an issue at low ISO.

(4) Larger sensors = better to create blurry backgrounds (i.e. smaller depth of field)

Yes, larger sensors give reduced depth of field for the same eFL and F-stop because of the larger physical lens aperture.

(5) Larger sensors = bring you closer to the actual focal length or focal range of a lens.

Huh? This is purely due to convention.

Most of us are used to thinking in terms of FLs for 35mm film cameras. The "crop factor" is simply the ratio 35mm_sensor_size/sensor_size. DSLRs typically have crop factors of 1--1.6. Many point-and-shoots have crop factors ~5--6. One could view cameras using bigger than 35mm film/sensor formats as having crop factors less than 1. (For instance, 70mm format would be crop factor ~.5.)

(6) Larger sensors = better range of aperture, especially small apertures such as f/19, f/22, etc. (assuming lens is capable of the range).

DSLRs typically all have similar (wide) F-stop ranges. P&Ses typically have (narrow) ranges of max (=F/2.8--F/4) -- F/8. The minimum on P&Ses is dictated by diffraction limits on the very small sensors.

Any thoughts on any of the above? Are they correct, incorrect and/or largely conditional on other factors? Any other huge benefits of a large sensor that I'm missing?

I think I have the above correct... Unfortunately, the info is spread over a number of websites--I think it can be found in various places on the following websites:
http://www.luminous-landscape.com
http://bobatkins.com/
http://ronbigelow.com/
http://www.kenrockwell.com
http://www.fredmiranda.com
http://www.clarkvision.com

Probably going with the EOS Rebel XSi unless the Canon EOS-5D Mark II is released over the next six months (it was not released today like many expected - canon announced a new EOS Rebel XS to replace the XT instead)

Looks like the XS is more a little brother to the XSi and a replacement for the XTi. http://www.pcworld.com/article/id,146899-c,digitalcameras/article.html

Don't forget that a good picture requires artistic vision (before or after the actual shot...) and the hardware is only a means to execute the vision.

Doug