Equivalent Lens Lengths

[Andysnap]

I was just trying to work out (and failing miserably) what the equivalent lens of a 90mm on a 6x9 camera would be on a cropped digital camera eg Nikon D300.

Any of you clever maths bods know?

Andy

 

[freecom2]

90mm FL = 6x9
~40mm FL = 35mm
~27mm FL = APS-C (D300)

The closest match will probably be a 28mm lens mounted on an APS-C camera.

 

[redddraggon]

It's a crop factor of 0.4

diagonal distance 35mm frame
diagonal distance 6x9 frame


(Can work it out using pythagoras theorem)

So a 90mm lens on 6x9 is about the same as 36mm on 35mm, or 24mm on APS-C.

 

[Andysnap]

Thanks a lot FC2 I had sort of guestimated around that but my maths is atrocious and I wasn't even vaguely convinced I was in the same ballpark.

Andy

 

[freecom2]

It's a crop factor of 0.4

diagonal distance 35mm frame
diagonal distance 6x9 frame


(Can work it out using pythagoras theorem)

So a 90mm lens on 6x9 is about the same as 36mm on 35mm, or 24mm on APS-C.

Thanks a lot FC2 I had sort of guestimated around that but my maths is atrocious and I wasn't even vaguely convinced I was in the same ballpark.

Andy

This link appears to use more maths to show it is 39mm:

http://www.oresteen.com/69lensdata.htm

 

[redddraggon]

This link appears to use more maths to show it is 39mm:

Apparantly 6x9cm film is not 60x90mm but 56 x 84 mm and that's why my maths gave a different answer :shrug:

I guess people are sloppier with measurements outside of academia :bang:

 

[Andysnap]

Thanks James, a slightly different result from FC2

Blimey, thats made my head hurt....

I want to retake an image that I took on the GW690 on digital and print it out to do a comparison. It doesn't need to be 100% exact but I would like to try and replicate the shot as nearly as possible to make it fair.

Just need to wait for a sunny day.....could be a while.

This was the shot


Warmingham-Church-Graves by andysnapper1, on Flickr

Cheers

 

[Andysnap]

Apparantly 6x9cm film is not 60x90mm but 56 x 84 mm and that's why my maths gave a different answer :shrug:

I guess people are sloppier with measurements outside of academia :bang:

I suppose it was easier to call it 6 x 9 than 5.6 x 8.4

 

[freecom2]

Apparantly 6x9cm film is not 60x90mm but 56 x 84 mm and that's why my maths gave a different answer :shrug:

I guess people are sloppier with measurements outside of academia :bang:

Their calculations were 57 x 83mm.

If I wanted to replicate, I'd use a mid-range DX zoom like a 17-55 that covers that range.

 

[Andysnap]

I've got an 18-135mm which is really sharp so should give a good comparison.

 

[excalibur2]

Talking about replicating shots....my 35mm shots didn't quite match the same view that were taken by cameras in 1916, they were sorta "now and then" shots. H'mm I suppose I should have used a plate camera

 

[Steve Smith]

It's easy. The long side of a 6x9 frame is 90mm - as is your lens.

So the equivalent lens length for a 24 x 36mm frame is equal to the long side. i.e. 36mm.

But to be really accurate

36/84 x 90 = 38.57mm


Steve.

 

[Andysnap]

Cool, thanks Steve.