focal length, and maximum magnification

so i was looking at which can focus closer...the 17-40L or the 15-85mm
looking at the specs here
http://www.the-digital-picture.com …Comp=100&Lens=6​75&Units=E
it lists the 17-40L as .25X, and the 15-85mm as .21X

plugging the minimum focus distance, and longest focal length into a dimensional field of view calculator shows the 15-85mm would photograph a much smaller area 6.2" vs. 3.4"

so...this leads to my question...which one can get a closer shot...and if it's the 15-85mm what's the value in .XX maximum magnification numbers?

It says the Canon 17-40L has a minimum focusing distance of 11.02" (28 cm). The Canon 15-85mm says it has a minimum focusing distance of 1.2' (36.58 cm).

Take Care,
Cheers, Patrick

Saint728 wrote in post #14831805
It says the Canon 17-40L has a minimum focusing distance of 11.02" (28 cm). The Canon 15-85mm says it has a minimum focusing distance of 1.2' (36.58 cm).

Take Care,
Cheers, Patrick

I know this- my point is at the minimum focus distance, and maximum focal length the 15-85mm would give a tighter shot even though it's max magnification is less supposedly

DreDaze wrote in post #14831857
I know this- my point is at the minimum focus distance, and maximum focal length the 15-85mm would give a tighter shot even though it's max magnification is less supposedly

Of course the 15-85mm will give you a much tighter shot then the 17-40mm, its more then twice as long on the maximum focal length side. Thats like comparing the Canon 70-200mm against the Canon 100-400mm. It list the 70-200mm at .17x and the 100-400 at .20x. Now which of these two lenses will give you a tighter shot?

Take Care,
Cheers, Patrick

Saint728 wrote in post #14832611
Of course the 15-85mm will give you a much tighter shot then the 17-40mm, its more then twice as long on the maximum focal length side. Thats like comparing the Canon 70-200mm against the Canon 100-400mm. It list the 70-200mm at .17x and the 100-400 at .20x. Now which of these two lenses will give you a tighter shot?

Take Care,
Cheers, Patrick

so then what's the point of maximum magnification numbers...i mean just looking at the numbers of .21X, and .25X i think most would assume you get a closer shot with the 17-40L at .25X...however, you can see in my examples what the results would actually look like...

so the higher magnification doesn't necessarily mean a closer shot

you're example doesn't work because the longer focal length lens has the higher magnification as well...

Keep in mind that not all zooms give their MM at their longest fl.

I really don't get what point your trying to make or find? It doesn't matter what the maximum magnification numbers are. At a longer focal length the larger it will be simple as that. If you have a 40mm lens the subject will be a lot smaller then if you have a 85mm lens.

The whole point of your thread it "so i was looking at which can focus closer...the 17-40L or the 15-85mm" Do you mean the minimum focusing distance or the largest magnification? If its the minimum focusing distance then the 17-40mm would be it. If you want the largest magnification then the 15-85mm would be it. If you want to see a similar example use your 50mm lens and take a picture of a subject then change the lens to your 100mm and take the same picture. You will find the 100mm will make your subject look bigger.

Take Care,
Cheers, Patrick

Saint728 wrote in post #14833414
I really don't get what point your trying to make or find? It doesn't matter what the maximum magnification numbers are. At a longer focal length the larger it will be simple as that. If you have a 40mm lens the subject will be a lot smaller then if you have a 85mm lens.

The whole point of your thread it "so i was looking at which can focus closer...the 17-40L or the 15-85mm" Do you mean the minimum focusing distance or the largest magnification? If its the minimum focusing distance then the 17-40mm would be it. If you want the largest magnification then the 15-85mm would be it. If you want to see a similar example use your 50mm lens and take a picture of a subject then change the lens to your 100mm and take the same picture. You will find the 100mm will make your subject look bigger.

Take Care,
Cheers, Patrick

Not always true, either. A 100/2.8 macro will give a larger picture, than any 200/300/400mm lens, due to it's MFD and MM. Now, with both lenses shooting from the same distance, there shouldn't be much/any difference.

I'm basically wondering about the maximum magnification number- previously I thought that the higher the number the more magnification you could get. With 1.00 being 1:1 magnification being the best(aside from the mp-e) I would think say a lens with .25 would be better than a .21, however as shown here the smaller magnification gives a better macro shot. So I'm basically wondering if the magnification number means anything.

And thanks for responding at all- I'm wondering if I should've posted in the macro talk section

1Tanker wrote in post #14833379
Keep in mind that not all zooms give their MM at their longest fl.

That must be it...I'd think for a zoom it would be a range for max magnification

It means that there is no way the 15-85 is still 85 at min focus distance. Magnification numbers are not relative to focal length.

it also has me wondering if the crop lens mag is relative to a crop sensor.

1Tanker wrote in post #14833445
Not always true, either. A 100/2.8 macro will give a larger picture, than any 200/300/400mm lens, due to it's MFD and MM. Now, with both lenses shooting from the same distance, there shouldn't be much/any difference.

So your telling me that there is much/any difference between the two focal length on the same subject at the same distance? I know for a fact the longer focal length lens will make the subject larger then it is with a shorter focal length lens.

A 100/2.8 macro will give a larger picture, than any 200/300/400mm lens, due to it's MFD and MM.

The 100mm f/2.8 lens will not give me a larger picture then a 200/300/400mm lens. If I take a picture at 50 feet away from the subject using the 100mm lens then take the same picture using a 200/300/400 from 50 feet away, the subject will definitely be larger.

Take Care,
Cheers, Patrick

The 100mm will make a larger picture because it can get MUCH closer. That's why lenses specify magnification figures. It reconciles the focal length + min focus distance into a comparable number.

The problem is that some zooms don't maintain their focal length (measured at infinity) when they focus close. Some lose nearly half their focal length. The 15-85 must be doing that to have a worse magnification at double the focal length of the 17-40.

Saint728 wrote in post #14833552
So your telling me that there is much/any difference between the two focal length on the same subject at the same distance? I know for a fact the longer focal length lens will make the subject larger then it is with a shorter focal length lens.

A 100/2.8 macro will give a larger picture, than any 200/300/400mm lens, due to it's MFD and MM.

The 100mm f/2.8 lens will not give me a larger picture then a 200/300/400mm lens. If I take a picture at 50 feet away from the subject using the 100mm lens then take the same picture using a 200/300/400 from 50 feet away, the subject will definitely be larger.

Take Care,
Cheers, Patrick

Yes, sorry.. i meant to say, that if you took the 100 macro, and a 70-200 at 100, and shot with both from the same distance(more than 5' say), they would give the same FOV(give or take any true differences in fl).

Saint728 wrote in post #14831805
It says the Canon 17-40L has a minimum focusing distance of 11.02" (28 cm). The Canon 15-85mm says it has a minimum focusing distance of 1.2' (36.58 cm).

Take Care,
Cheers, Patrick

The 15-85 is specified at 35cm, The 1.2 ft is only an approximation. I can achieve focus with my copy at around 32 -33 cm at both the wide end and the long end.