Canon PowerShot G9 - confusing Focal Length

[Winblows]

This camera is my travel companion and a "party freak". I wonder, what is the really 35mm film equivalent for this lens ?

Canon states, that the lens has:
"Focal Length 7.4-44.4mm f/2.8-4.8 (35mm film equivalent: 35-210mm)"

Elsewhere, the WikipediA tells, that for a Canon lens
" ... Typical crop factors are 1.5x for Nikon APS-C ("DX") format, 1.6x for Canon APS-C format ..."

so, what IS the 35mm equivalent for this lens ?

 

[otherprof]

This camera is my travel companion and a "party freak". I wonder, what is the really 35mm film equivalent for this lens ?

Canon states, that the lens has:
"Focal Length 7.4-44.4mm f/2.8-4.8 (35mm film equivalent: 35-210mm)"

Elsewhere, the WikipediA tells, that for a Canon lens
" ... Typical crop factors are 1.5x for Nikon APS-C ("DX") format, 1.6x for Canon APS-C format ..."

so, what IS the 35mm equivalent for this lens ?

The G9 does not have an APS-C size sensor. APS-C sensors are in the DX Canon DSLRs. The senors in the G series are smaller. Canon is correct in what they state for your lens on your camera.

 

[KmH]

Yep!
The G9 has a 1/1.7” sensor, the second smallest image sensor made, and has a 4.2x crop factor.
Crop factor - Wikipedia the free encyclopedia
Image sensor format - Wikipedia the free encyclopedia

7.4 mm x 4.2 crop factor = 31.08 which Canon has generously rounded to 35.
44.4 mm x 4.2 crop factor = 186.48 which Canon has even more generously rounded to 210 mm.
Canon has rounded up so drastically for marketing purposes.

 

[Winblows]

Yep!
The G9 has a 1/1.7” sensor, the second smallest image sensor made, and has a 4.2x crop factor.
Crop factor - Wikipedia the free encyclopedia
Image sensor format - Wikipedia the free encyclopedia

7.4 mm x 4.2 crop factor = 31.08 which Canon has generously rounded to 35.
44.4 mm x 4.2 crop factor = 186.48 which Canon has even more generously rounded to 210 mm.
Canon has rounded up so drastically for marketing purposes.

Great! I'm looking for a the "WIDE ANGLE CONVERTER LENS WC-DC58B 0.75x".
31,08x0,75=23,31mm

 

[tirediron]

Yep!
The G9 has a 1/1.7” sensor, the second smallest image sensor made, and has a 4.2x crop factor.
Crop factor - Wikipedia the free encyclopedia
Image sensor format - Wikipedia the free encyclopedia

7.4 mm x 4.2 crop factor = 31.08 which Canon has generously rounded to 35.
44.4 mm x 4.2 crop factor = 186.48 which Canon has even more generously rounded to 210 mm.
Canon has rounded up so drastically for marketing purposes.

Great! I'm looking for a the "WIDE ANGLE CONVERTER LENS WC-DC58B 0.75x".
31,08x0,75=23,31mm

Well stop! Unless you really hate producing nice images, you don't want one of those. Your image quality will suffer horribly.

 

[Braineack]

7.4 mm x 4.2 crop factor = 31.08 which Canon has generously rounded to 35.
44.4 mm x 4.2 crop factor = 186.48 which Canon has even more generously rounded to 210 mm.
Canon has rounded up so drastically for marketing purposes.

how is a x 4.729... crop factor more generous than a x 4.729... crop factor?

it's also really odd that 35 / 7.4 = 4.729...

maybe what we learned is that KmH is just really bad at math.

edit: although when I do the real math I get a crop factor of 4.623656. but then again a d800 is technically larger than 35mm film.

but I'm guessing canon's "rounding" is close enough.

 

[nerwin]

The "true" 35mm equivalent focal lengths are 34.78mm - 208.68mm in case you were wondering. lol.

 

[Derrel]

Yep!
The G9 has a 1/1.7” sensor, the second smallest image sensor made, and has a 4.2x crop factor.
7.4 mm x 4.2 crop factor = 31.08 which Canon has generously rounded to 35.
44.4 mm x 4.2 crop factor = 186.48 which Canon has even more generously rounded to 210 mm.
Canon has rounded up so drastically for marketing purposes.

The "true" 35mm equivalent focal lengths are 34.78mm - 208.68mm in case you were wondering. lol.

So...which one of you is correct about this? I don;t feel like looking this up.

Whaddaya' say, dueling HP Scientific Calculators at 10 meters at noon, tomorrow?

 

[nerwin]

Hmmm..I did some research and figured out the G9's 1/1.7" sensor has a crop factor of 4.55. So technically speaking a 7.4-44.4mm lens with a 4.55 crop factor would give a it a 35mm equivalent FOV of 33.67mm-202.02mm.

 

[Braineack]

Pretty sure 4.55 assumes a 9.45mm sensor; the G9 sensor is slightly smaller at 9.3mm:

The G9 sensor is 7.44 x 5.58 mm.

a² + b² = c²

7.44² + 5.58² = c²

55.3536 + 31.1364 = 86.49²

√86.49² = 9.3mm

35mm/Full Frame: √1876 = 43mm

43 / 9.3 = 4.623656~ crop factor

so a 7.4-44.4mm lens on a G9 sensor would be 34.22mm - 205.3mm if that's correct.

Canon seems to have used 4.729... as their crop factor in determining the equivalent--either they just liked the round numbers is gave them better, or the sensor actually is even smaller at 9.1mm.


Either way, 31-186.5mm, or 33.6-202mm, or 34.2-205mm, or 35-210mm--you got a pretty darn close ballpark.

 

[Winblows]

Well stop! Unless you really hate producing nice images, you don't want one of those. Your image quality will suffer horribly.

Thanks for the advice. I've got a "LA-DC58H Conversion Lens Adapter" on a flee market, so I wanted to try the "WC-DC58B 0.75x" (if I could get it cheap).

 

[Winblows]

... and thank you all guys for the great help !

 

[Derrel]

Pretty sure 4.55 assumes a 9.45mm sensor; the G9 sensor is slightly smaller at 9.3mm:

The G9 sensor is 7.44 x 5.58 mm.

a² + b² = c²

7.44² + 5.58² = c²

55.3536 + 31.1364 = 86.49²

√86.49² = 9.3mm

35mm/Full Frame: √1876 = 43mm

43 / 9.3 = 4.623656~ crop factor

so a 7.4-44.4mm lens on a G9 sensor would be 34.22mm - 205.3mm if that's correct.

Canon seems to have used 4.729... as their crop factor in determining the equivalent--either they just liked the round numbers is gave them better, or the sensor actually is even smaller at 9.1mm.


Either way, 31-186.5mm, or 33.6-202mm, or 34.2-205mm, or 35-210mm--you got a pretty darn close ballpark.

Sensors are always larger than the area used to create the image; that is called "masking"...so it makes sense that if the sensor's outside dimensions would calculate to a 4.623656x crop factor, that masking off even a few pixels could easily lead to a net FOV factor of 4.729....