Originally posted by UncleVanya Two problems with built in slide out hoods:
1) Not narrow enough on crop.
2) Friction doesn't hold up over time and the hood tends to slide back closed as you tilt up the lens.
Clear advantages:
- You can't lose them or forget them at home.
- They don't take up a meaningful amount of space when you don't use them
Possible advantages:
- They don't necessarily collide with filters & lens caps (if you use the right kind of lens cap) like screw-in and clip-in hoods
- Variable length (if they have enough friction to stay in place)
Disadvantages:
- Their length and shape is restricted by the design of the lens barrel (this one's quite ample but they're often too short)
I had a full set of Canon nFD lenses with 52mm filter threads for a while (24/2, 28/2, 35/2, 50/1.4, 85/1.8, 100/2), they all used the same hood bajonet and while they all had dedicated hoods (BW-52C, BW-52B, BW-52A, BS-52, BT-52),
the hoods were all interchangeable, a 24mm hood still gives some protection on a 35 or 50 and a somewhat longer hood still works on a wider lens (exchanging more soft vignetting for extra flare protection).
Unfortunatelly, only the BW-52C and BW-52B had petal shapes, I would have liked some longer petal hoods (I know the petal hood for e.g. the 100/2 would be quite long but I could always use one of the shorter ones).
Ideally, some lenses would have oversized bajonet mounts, so hoods could be intercompatible across a wider range of lenses.
The Canon nFD 135s & 200s don't have hood bajonets but the 52mm filter thread spans from 24mm to 200mm (within that range, only the 35/2.8 tilt-shift and the 85/1.2 have larger threads), so the lens caps are all interchangeable, so could the hoods be.
A (mostly) universal hood bajonet would add some bulk to the smaller lenses but I think that would be well worth it.
(Canon nFD nFD 300/5.6, 100/2, 50/1.4, 35/2, 28/2 & 24/2.8)
EDIT: Dammit, now my brain has latched on to the standardisation idea...
First, we'll adjust the most common prime focal lengths a bit to deal with the crop issue:
(10) - 15 - 23 - 35 - 55 - 85 - 130 - 200 - 300 - (450)
The ratios between the steps are now all between 1.5 and 1.57, so to get an APS-C lens hood for your FF lens, you just buy the hood for the next-longer prime lens.
A secondary set of steps could look like this (ratios between 1.5 and 1.56):
(13) - 20 - 30 - 45 - 70 - 105 - (160) - (240) - (360)
The lens hood bajonet needs to be slightly larger than the filter thread anyway, so we tie the two together.
Something like 77mm across the board would add too much bulk to all the smaller lenses but we
do want 85/1.4's and 130/2's.
72-82mm would work as the largest thread (with a corresponding hood bajonet), we should be able to cover anything from 20/1.4 to 130/1.8.
Next we'll need a thread size that can cover anything except the largest primes, things like a 35/1.4, 55/1.4 and 85/1.8 should fit here.
Something like
58-67mm should have us covered, a prime lineup like this should be possible:
20/2.8 - 23/2 - 30/1.8 - 35/1.4 - 55/1.4(1.2?) - 85/1.8 - 105/2 - 130/2.4
As for zooms, a 15-35/4 or 23-105/4 would probably need the larger thread/bajonet but a 23-70/4 & 70-200/4 as well as variable-aperture lenses like 20-45/3.5-4.5, 23-130/3.5-5.6 or 70-300/4-5.6 would fit here.
I'm not sure if we'd really need a small 3rd standard but a set of small primes (with diameters around 65mm and below) with
49-55mm threads could work:
23/2.8 - 30/2 - 35/1.8 - 55/1.8 - 85/2 - 130/2.8(3.5?)
Overall, we should leave some room for lens design and pick the larger side for all 3 standards (55mm, 67mm, 82mm).
Apart from extreme wide angle lenses and fast tele lenses (105/1.4, 200/2, 400/2.8, 200-400/4, etc.), we'd have everything covered and would never need filters or lens caps in any but these 3 sizes.
There would be some options for backward compatibility, e.g. step-up rings with bajonet hoods on the outside to bring old lenses into the new standard.
Last edited by Boris_Akunin; 07-19-2018 at 03:10 PM.