How Fast?

for DSLRs
Do these 8 images all look about the same to you? The differences are not obvious. I created this set of images to answer some questions that were bugging me, such as:

  1. How different is a shot at 1.2 from 1.4? ( Compare panel 1 with 2)
  2. Does a 1.2 lens used at f4 look much different from an f4 lens at f4? (Compare panel 3 with 5)
  3. Does a longer but slower lens give you the same shallow depth of field look as a shorter but faster lens? (compare panel 1 with 7)

Bottom Line: It doesn't make sense to buy a fast lens and generally use it mostly stopped down. An f1.2 image is not VASTLY different from one at f1.4.

I ran into some problems with this series. First, there was a small tungsten lamp that I used to help with focus. The main light in each shot was a Canon flash set to TTL so I could easily change the f-stop and get a similar exposure. HOWEVER, at 1.2, the yellow from the little focusing lamp is actually pretty visible — in the first panel. Also when you vary exposure by letting the TTL flash ramp up and down its power it seems you get subtle color shifts. When the flash gives you less light it uses a shorter flash, which will cause color shifts, even in digital.
85mm 1.2
85mm 1.4
85mm f4
85mm f16
zoom f4
zoom f16
180 3.5
180 f16
85mm 1.2
85mm 1.4
85mm f4
85mm f16
zoom f4
zoom f16
180 3.5
180 f16
85mm 1.2
85mm 1.4
85mm f4
85mm f16
zoom f4
zoom f16
180 3.5
180 f16
Left
Right

These are shot with the Canon 85mm f1.2 lens, which is among the fastest lenses available. It is very costly, heavy and highly worshipped by many photographes for two reasons: it allows you to shoot in VERY low light; it produces a very intense look with very little depth of field.

Notice that there is some yellow cast on the left side of Nicole's face. There was a small tungsten focusing lamp which emitted enough light to affect the 1.2 exposure.

If you start to close down the Canon 85 f1.2 to 1.4 you lose a tiny amount of that fast lens look - but not very much. So before you pay the big bucks for that extra f stop try some rentals and tests.

On the other hand, if you close down to f4, you do lose most of that "fast lens look". In which case, you don't have to be shooting with a 1.2 lens.

If you close down to f16, you are not making use of almost all of the glass in the lens. It is not wrong to stop this lens down to 16, but it would not make sense to buy this lens unless you use if most often at f1.2 to f1.8.

This is a Canon 24-105 zoom set at roughly 85mm, and shot at f4. I don't see much difference between this and the f1.2 lens used as f4.

Also the Canon 24-105 zoom set at roughly 85mm, and shot at f16. This looks the same as the 1.2 85 when shot at f16.

The 180mm Canon macro lens, wide open at f3.5. How does this compare to the look of the 85mm at 1.2 or 1.4? Does the narrow focus work as well? And the look of the image is different due to the longer focal length.

The 180mm Canon macro lens, shot at f16. This look does not look too much different to me than the 85mm 1.2 at f16 (panel 4) or the 24-105 at f16 (panel 6).

These are shot with the Canon 85mm f1.2 lens, which is among the fastest lenses available. It is very costly, heavy and highly worshipped by many photographes for two reasons: it allows you to shoot in VERY low light; it produces a very intense look with very little depth of field.

Notice that there is some yellow cast on the left side of Nicole's face. There was a small tungsten focusing lamp which emitted enough light to affect the 1.2 exposure.

If you start to close down the Canon 85 f1.2 to 1.4 you lose a tiny amount of that fast lens look - but not very much. So before you pay the big bucks for that extra f stop try some rentals and tests.

On the other hand, if you close down to f4, you do lose most of that "fast lens look". In which case, you don't have to be shooting with a 1.2 lens.

If you close down to f16, you are not making use of almost all of the glass in the lens. It is not wrong to stop this lens down to 16, but it would not make sense to buy this lens unless you use if most often at f1.2 to f1.8.

This is a Canon 24-105 zoom set at roughly 85mm, and shot at f4. I don't see much difference between this and the f1.2 lens used as f4.

Also the Canon 24-105 zoom set at roughly 85mm, and shot at f16. This looks the same as the 1.2 85 when shot at f16.

The 180mm Canon macro lens, wide open at f3.5. How does this compare to the look of the 85mm at 1.2 or 1.4? Does the narrow focus work as well? And the look of the image is different due to the longer focal length.

The 180mm Canon macro lens, shot at f16. This look does not look too much different to me than the 85mm 1.2 at f16 (panel 4) or the 24-105 at f16 (panel 6).