A New Constant f/4 Aperture RF-S Zoom Coming

[Michael Clark]

*IF* this lens has any degree of weather sealing it would solve the lens dilemma I've been struggling with and will be an insta-buy for me. But this is RF-S so I'm fully expecting that it will continue the budget build quality tradition. It will definitely cause me to wait and see whether it pans out before going with another option, though.

Coming from the M43 world I didn't entirely realize how spoiled they are for hiking/travel lenses. All sorts of 24-xx (equivalent) options many with robust build and weather sealing at a range of aperture/size/cost. I'm trying to find 'that lens' for my R7. Maybe I'm over-valuing weather resistance, but being in the dusty SW and having been caught in weather when traveling far too frequently I'm far more comfortable having it. (we got drenched several times on a trip to NZ and the E-M1.2/12-100 came through with aplomb)

The only RF-S lens with any advertisement of splash/dust resistance is the Sigma 17-40 which is probably the most logical choice, but I'm unreasonably annoyed that it's 17 rather than 15 on the wide end. And general hiking/travel really doesn't need F/1.8 so there's a size penalty. I find myself very seriously considering the RF 14-35/4 as it seems the best fit - 22-56 equivalent (maybe even a bit wider if you manually tweak the corrections), L build quality, reportedly great optically even with the corrections (and APS-C avoids the worst of the corrections in the first place); just evaluating whether paying the premium for an FF ultra-wide (albeit a fairly reasonably priced one) is worth it.

Weather resistance is pretty easy to do fairly cheaply. I've used the same two OP/TECH rain covers dozens of times over the past 15+ years. I can't believe they've held up so well. I figured they would be more or less disposable. I think I have another bag or two of them socked away somewhere in the house, but I've not yet needed to replace the two in my camera bag. I have used a cheaper no-name brand with room for a flash and they do tend to tear sometimes.



I've shot field sports in all kinds of weather, and community parades in downpours. I have yet to have any issues with any of my gear due to water or dust.

 

[Michael Clark]

Yes. For complex lenses, the entrance pupil may be very different than the front element size. I'm fuzzy on the relationship; this is what Google tells me: "The entrance pupil in a complex lens is determined by imaging the physical aperture stop through all preceding optical elements into object space. It is the virtual or real image of the diaphragm as seen from the front of the lens, defining the cone of light that enters the system."

Of course. And field of view depends on the focal length and the sensor size.

At narrow angles of view (i.e. telephoto lenses) the EP and the front element are pretty much the same size, give or take 10% or less. It's wider angle lenses where the EP is a virtual image often located well behind the physical aperture diaphragm.

 

[Michael Clark]

Thinking more about the 15-70/4, I find it somewhat interesting that it's not quite a direct head-to-head competitor to either of the Sigma normal zooms, but that the Tamron 17-70 IS which IS a bit more of a direct competitor never appeared for RF-S. Makes me wonder whether Canon did actively prevent Tamron from offering that lens in RF-S mount.

I still wish this would have L-grade construction, but it seems far more likely that it'll be on the level of the budget FF STM lenses.

The absence of the 17-70 does indeed make more sense now, that was Tamron’s only mirrorless APS-C lens that didn’t directly compete against a superior Sigma alternative on RF mount, and one that would’ve been popular with the RF-S bodies lacking IBIS (4/5 currently).

If the construction isn’t L caliber, I hope it’s at least along the lines of the RF 28-70 f/2.8.

Things that make you go, "Hmmmm?"

 

[Michael Clark]

Update: My point is that the DOF of a lens is entirely independent of the size of the sensor which receives its image.

Except it's not unless you enlarge images from all sensors by the same factor and your FF images are thus 1.6X larger than your APS-C image. If you enlarge images from differently sized sensors to the same display size, you enlarge the smaller images by a greater factor, thus enlarging the blur in those images by a greater factor. Some blur that is not perceptible as blur at a smaller enlargement factor will be perceptible as blur at the higher enlargement factor.

If you take the same exact digital file and view it at two different display sizes from the same distance, the DoF changes! You can even view the same displayed image from two different distances and the DoF changes!

Two things determine Depth of Field: aperture and total magnification. The lens only fully controls one of those factors. Total magnification is determined by subject distance, focal length, the enlargement ratio from the image size projected onto the sensor to the image size as displayed when viewed, the viewing distance from the displayed image to the viewers eyes, and even the viewer's visual acuity which determines the smallest arcminute (under near ideal lighting conditions for a person with 20/20 vision the limit is right at 1 arcminute) or arcseconds of angle that is perceivable as blur.

 

[Michael Clark]

Neuro, once again you prove that you're an obnoxious bully.

That he is, but on this point he is also correct.