Lens power - Eos 30D w/ 75-300mm vs SX60hs @ 300.

[Saluki]

New to digital SLRs and just got my first - a nice Eos 30D w/ the 75-300 lens. I have been using an SX60HS for about 6 years and wanted to compare it to the "new" Eos. Took similar shots with both, at 300mm.  Was surprised to see the Eos gave greater enlargement than the SX60 at the same apparent focal length.  300mm with the Eos looks like about 400 on the SX.  Why is that?

[rs-eos]

Sensor size.  At the same focal length, sensor size drives the field-of-view.   The SX60HS sensor is tiny compared to the APS-C sensor of the 30D.  The 30D would thus give you wider field-of-view for the same focal length used on your SX60HS.

[Saluki]

Ah....thanks.

[jrhoffman75]

To expand on Ricky's answer. Consumer cameras frequently provide focal length as 35mm equivalent since folks moving to those digital cameras frequently come from film point and shoot cameras.

As shown below, canon describes the actual focal length of the lens (which is less than 300mm) and the 35mm equivalent (which can go to greater than 1300mm equivalent). The camera may be reporting 35mm equivalent.

Digital SLRs don't/can't do that since the camera computers don't do the equivalency calculations. A 300mm lens on a crop sensor 30D is still a 300mm lens; but because of the 1.6 crop factor it gives the same field of view as a 480mm lens on a full frame (35mm equivalent) sensor.

[ebiggs1]

This is called the telephoto addvantage for folks with smaller than 35mm frame size cameras. On the other side of the coin there is a WA disadvantage for the smaller sensor folks.

[MikeSowsun]

Here is a little more info for you:

Your SX60hs has a 3.8-247mm lens with a 5.5 crop factor, which is equivalent to 21-1365mm.

Your 30D has a 75-300mm lens with a 1.6 crop factor, which is equivalent to 120-480mm.

When you set the SX60hs to “300”, it was actually at 55mm but you were reading the equivalent focal length of 300mm. The 30D set to “300” was equivalent to 480mm and that explains why it gave greater enlargement. 

[Saluki]

So the 30D with the 75-300 is actually giving me the equivalent of 120-480mm, yes?

[MikeSowsun]

Yes, 120-480mm when compared to a standard “Full Frame” 35mm film camera or DSLR with a

24mm x 36mm image sensor. 

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