Cropped Sensor - Explain to a Noob

[DampCat]

I understand the concept of the cropped sensor and what that means compared to a full frame (um.. is this correct context?) camera... but how do i work out the adapted lengths?

For example, i have an EOS 10D... i'm not sure of the sensor size, but presumably it's not full frame or anywhere close... so at 18mm, my 18-55 is actually how wide? And how do i work this out? Is there a formula?

I really interested in getting a 10-20 (or more likely 10-22 Sigma/Tamron given my budget) but if my 10D will reduce the width too much there wont be much point. What will the width actually be?

 

[Raikiri]

On Canons crop sensors you get a 1.6x view of what you would get on full frame/35mm.

So a 100mm lens shows what a 160mm would on 35mm, 18 is 28.8mm etc. It's not quite as clean cut as that, but it's all you really need to know.

 

[Paul_Canning]

What are the advantages/disadvantages to having a cropped sensor?

 

[Mr Jones]

Advantage: Longer focal length for the same lens mounted on a FF. Useful for sports/wild-life photography.
Disadvantage: More noise than FF. DoF isn't as 'thin' as a FF camera on the same f no.

That's the major difference that I can think of off the top of my head.

The Sigma/Canon 10-20mm will be 16mm when mounted on OP's cropped sensor (1.6x), 16mm is ridiculously wide - the perception of wider angles even at a few mm lesser gives more WOW than a few more mm on the tele end imo.

 

[Raikiri]

+
Generally cheaper.
Smaller/lighter bodies
Longer reach with the same lenses - so a 300mm f2.8 is equivilent to a 480mm f2.8
Greater DOF - Can be useful in some situations, or a pain in the arse
Better for Macro

-
Lenses aren't as wide - you would need a 10mm for the equivilent to 16mm on full frame.
Poorer build quality - usually more to do with the price point, but being used in lower end products they often aren't made as well.
Poorer high ISO performance - smaller gaps between the image sites leads to noise/errors

 

[DampCat]

So my 10mm would be 16mm? That's still pretty wide.
And the cheapest FF camera from Canon is the old 5D at ~£800?

Bleh!

 

[D.P.]

+
Generally cheaper.
Smaller/lighter bodies
Longer reach with the same lenses - so a 300mm f2.8 is equivilent to a 480mm f2.8
Greater DOF - Can be useful in some situations, or a pain in the arse
Better for Macro

-
Lenses aren't as wide - you would need a 10mm for the equivilent to 16mm on full frame.
Poorer build quality - usually more to do with the price point, but being used in lower end products they often aren't made as well.
Poorer high ISO performance - smaller gaps between the image sites leads to noise/errors

"Poorer build quality - usually more to do with the price point, but being used in lower end products they often aren't made as well."

This isn't true, especially for Nikon. The D100,200 and 300 are built like a tank. The Canon 7D is pretty solid. The Canon 1D series are 1.3x crop sensor...

Also, the cropped sensor doesn't mean you always have worse noise. Simply, the smaller sensor mean that if the same number of pixels are present each pixel is smaller allowing less light to be detected. a 12 MP Cropped sensor has the same pixel density as a 20MP Full fame (on Canon).



One noticeable difference between DX and FX sensors is on lens quality. If the cropped sensor has a higher pixel density it will require better lenses to achieve the same sharpness of image. FX can be more forgiving, until you end up at the high pixel densities again like the 24MP Nikon D3X. However, as an advantage, if you use full frame lenses on a cropped sensor then the central image area normally has the best quality which is an advantage of cropped cameras.


If sensor design keep cropped sensor to 12MP then DX is just fine for 99% of people. Unfortunately Nikon is the only to do this. Forcing 18Mp on a cropped sensor is a real waste.

 

[Mr Jones]

So my 10mm would be 16mm? That's still pretty wide.
And the cheapest FF camera from Canon is the old 5D at ~£800?

Bleh!

It is indeed still pretty wide.
The widest cropped sensor lens is, AFAIK, the Olympus 7-14mm Zuiko Digital F4 lens, 14-28mm equiv. The Sigma/Canon is the widest for a Canon without resorting to going down the FF route (Much much bigger, expensive and will show more imperfections of cheaper lenses).

If sensor design keep cropped sensor to 12MP then DX is just fine for 99% of people. Unfortunately Nikon is the only to do this. Forcing 18Mp on a cropped sensor is a real waste.

Not trying to sound like a fanboi but the Olympus 4/3 also keeps the MP down for same reason, no point cramping in so many pixels in a cropped sensor where it'll just noise creep anyway.

 

[growse]

Another advantage of crop is that there's less data for the camera to process off the sensor, generally. So burst rates tend to be higher.

 

[Raikiri]

"Poorer build quality - usually more to do with the price point, but being used in lower end products they often aren't made as well."

This isn't true, especially for Nikon. The D100,200 and 300 are built like a tank. The Canon 7D is pretty solid. The Canon 1D series are 1.3x crop sensor...

Which is why I specifically mentioned price, referring to the entry level models. Obviously I didn't mean a £3,000+ 1D series.

Also, the cropped sensor doesn't mean you always have worse noise. Simply, the smaller sensor mean that if the same number of pixels are present each pixel is smaller allowing less light to be detected. a 12 MP Cropped sensor has the same pixel density as a 20MP Full fame (on Canon).

But I was comparing like for like, obviously the pixel density will vary if you're comparing two sensors with wildly different pixel counts.

 

[D.P.]

Another advantage of crop is that there's less data for the camera to process off the sensor, generally. So burst rates tend to be higher.

This is only true if the cropped sensor has less resolution, which they often do but not always.

E.g., a Nikon D300s has to shift the same pixels as a D3s.

 

[D.P.]

Which is why I specifically mentioned price, referring to the entry level models. Obviously I didn't mean a £3,000+ 1D series.




But I was comparing like for like, obviously the pixel density will vary if you're comparing two sensors with wildly different pixel counts.

Yeah, comparing the 12Mp D3s and D300s shows the difference full frame can make.

The thing is, Canon don't sell a modern Full Frame camera with something like 12MP to achieve ultra low noise. The 21Mp sensors have a similar pixel pitch to a 12 Mp cropped sensor.