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09-27-2022, 06:18 AM - 2 Likes   #1
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Where have all the f/3.5-4.5 zooms gone?

This isn't specific to Pentax by any means but when I look at older zoom lenses I see there are lots of f/3.5-4.5 or similar around. They may not be exactly that but the point is that on the long end they aren't f/5.6. Nowadays almost all zooms are either constant maximum aperture or f/3.5-5.6, so slower on the long end. No-one tries to make variable-aperture zooms not quite so slow at the long end any more and it's a shame as it provides something a bit better without going to the size/weight/cost of a constant aperture zoom.

Am I the only one who has noticed this?

09-27-2022, 06:36 AM   #2
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QuoteOriginally posted by Jonathan Mac Quote
This isn't specific to Pentax by any means but when I look at older zoom lenses I see there are lots of f/3.5-4.5 or similar around. They may not be exactly that but the point is that on the long end they aren't f/5.6. Nowadays almost all zooms are either constant maximum aperture or f/3.5-5.6, so slower on the long end. No-one tries to make variable-aperture zooms not quite so slow at the long end any more and it's a shame as it provides something a bit better without going to the size/weight/cost of a constant aperture zoom.

Am I the only one who has noticed this?
Now that you've mentioned it...

I'm guessing they've been superseded by f/4 zooms, like Fuji's 16-80/4 and Nikon's 24-70/4.
09-27-2022, 07:21 AM - 4 Likes   #3
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I think the issue is the following, the faster zooms we’re made at a time when the maximum ISO was 400 from the film era.

My K1MKII probably has better overall image quality at 10x that ISO. I have posted some shots even at 25600 ISO. Are they gallery quality prints, no, I freely admit that, and they have a bit of noise, but….. are they good enough to capture the image accurately. YES.

So why do you need ultra fast lenses today. And remember many of these are consumer lenses, you can still go out and get constant aperture F2.8 in the range of 20ish mm to 70ish mm and from 70-200mm, you just pay a lot, like you always did.

Edit note. My *istD (circa2003) had better image quality at ISO800 than the best 400ISO film I ever used.
09-27-2022, 07:22 AM - 1 Like   #4
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I think also in the age of cleaner higher ISO and shake reduction, the need for a faster aperture at long zoom is negated. Sure you may be losing 3/4 of a stop in terms of DOF, but the difference between 4.5 and 5.6 is pretty small.

09-27-2022, 07:30 AM   #5
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Actually I’m seeing a lot of f4-5.6 zooms and I think that’s due to the changes in high iso functionality. I think there’sa tolerance for slower lenses that comes from being able to shoot at higher iso. Look at the 55-300 PLM as another example of aperture getting slower. Size and weight are very important to todays consumer.
09-27-2022, 07:43 AM - 2 Likes   #6
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I'd add in-body shake reduction and next gen post-processing advances to the ISO factor.

The DOF trade-off is size/weight and reduced cost.
09-27-2022, 10:11 AM - 2 Likes   #7
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Main reason is optics. The definition of F-stop is:
f/stop = focal length / diameter of effective aperture (entrance pupil) of the lens
The kit lens is 18-55mm f3.5-5.6. That's a 3 x zoom ie 3 x 18 = 54. There would nominally be a commensurate corresponding shift in F number of 3 stops. However lenses are typically designed to have a lesser change than the change in focal length would warrant. You can get an impression of how much you can zoom before the f-stop changes with the lens on the camera, metering off eg a white wall (an approximate measure, the camera exposure changes in steps of 1/2 or 1/3 stop depending on your camera settings).

Old film kit lenses were typically something like 28-70mm, =2.5x zoom, and f3.5-4.5 would have been pretty typical for these. I guess it was relatively straightforward to design these lenses like this, specifically because they were typically retrofocus designs with a large negative front element, so I guess the entrance pupil could also change while zooming through the wide angle focal range. There are also lenses where you can see the iris change size as you zoom.


Last edited by marcusBMG; 09-27-2022 at 11:28 AM.
09-27-2022, 12:13 PM - 1 Like   #8
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QuoteOriginally posted by marcusBMG Quote
Old film kit lenses were typically something like 28-70mm, =2.5x zoom, and f3.5-4.5 would have been pretty typical for these. I guess it was relatively straightforward to design these lenses like this, specifically because they were typically retrofocus designs with a large negative front element, so I guess the entrance pupil could also change while zooming through the wide angle focal range. There are also lenses where you can see the iris change size as you zoom.
Quite a few longer zoom ranges were available with the f3.5-4.5 aperture range in question. The 35-135 was one I used for a long time on my film PZ-1. What I see in looking back is that the longer lenses tended to end with f5.6 but the shorter often ended their open aperture range at f4.5 rather than slower.

SMC Pentax-F 35-135mm F3.5-4.5 Reviews - F Zoom Lenses - Pentax Lens Reviews & Lens Database

SMC Pentax-FA 24-90mm F3.5-4.5 AL [IF] Reviews - FA Zoom Lenses - Pentax Lens Reviews & Lens Database

SMC Pentax-A 35-210mm F3.5-4.5 Reviews - A Zoom Lenses - Pentax Lens Reviews & Lens Database
09-27-2022, 06:08 PM - 1 Like   #9
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It has to do with zoom range too,
Most of the older zooms were 2 to 3X (35-70, 50-150 etc), many current zooms are 4 to 6X (18-135, 55-300, etc) and longer,
Harder to only have a stop or two change over such a longer focal length.
09-27-2022, 06:19 PM   #10
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QuoteOriginally posted by K-Three Quote
It has to do with zoom range too,
Most of the older zooms were 2 to 3X (35-70, 50-150 etc), many current zooms are 4 to 6X (18-135, 55-300, etc) and longer,
Harder to only have a stop or two change over such a longer focal length.
35-135 is 3.8x, 35-210 is 6x. I suspect it has to do with consumer demand for lighter lenses and a tolerance for slightly slower aperture in design choices due to not being limited by film iso.
09-27-2022, 07:52 PM   #11
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I believe the older f/3.5-4.5 where fast zoom of these days, when constant aperture f/2.8 zooms were rare. And it probably also comes from manual focus zooms where slower aperture did not work well with the focus aid.

Now we have the choice of faster constant aperture or slower variable aperture. I guess there is not much room for something in between. The difference between a constant f/4 zoom and a variable f/3.5-4.5 would be too small.

Last edited by Fogel70; 09-27-2022 at 08:16 PM.
09-28-2022, 12:39 AM   #12
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Shooting low light nowadays is easy with the great low noise / high dynamic range sensors combined with shake reduction. Slower and more compact zooms are more attractive for that. In case you want to ply with small depth of fields you can choose for the F2.8 zooms, although heavy and expensive. Better for that are faster primes, even the low budget manual focus K/M/A era lenses perform great for that purpose. You grab a pristine M-1.4/50 for very little on Ebay and Market Place and these lenses deliver great IQ on 36 Mp FF.
09-28-2022, 03:29 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
I think the issue is the following, the faster zooms we’re made at a time when the maximum ISO was 400 from the film era.

My K1MKII probably has better overall image quality at 10x that ISO. I have posted some shots even at 25600 ISO. Are they gallery quality prints, no, I freely admit that, and they have a bit of noise, but….. are they good enough to capture the image accurately. YES.

So why do you need ultra fast lenses today. And remember many of these are consumer lenses, you can still go out and get constant aperture F2.8 in the range of 20ish mm to 70ish mm and from 70-200mm, you just pay a lot, like you always did.

Edit note. My *istD (circa2003) had better image quality at ISO800 than the best 400ISO film I ever used.
I think the "digital sensors are far better at high ISO than film ever was so there's no need for lens speed" argument has long since been debunked as nonsense. If it were true then there's be no lenses available today, prime or zoom, faster than around f/4, simply because that provides at least equal IQ as what we had in the film days. What was available at the peak of film is not any kind of established standard of what's "good enough". All else being equal, faster is always better, regardless of the qualities of sensors.

I suppose making variable-aperture zooms slower is a push from manufacturers to buy their constant-aperture zooms or fast primes but the flip-side of that is that they're offering poorer value in the variable-aperture zooms. Canon, always the first to make their products poorer value, have released APS-C kit lenses for their mirrorless mount APS-C cameras that are f/4.5-6.3. After all, why should the customer benefit from improved image quality by using a lower ISO when we can charge the same as in the past for a kit lens that's 2/3s of a stop slower than previously and keep the extra money?
09-28-2022, 03:56 AM   #14
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I rather suspect the ultra-short focal length everything-in-focus lenses fitted in the majority of modern 'phones has numbed the requirements of the current generation of up-coming photographers, many of whom seem to have no concept of using selective focus at exposure time, preferring to rely on a plug-in or app to provide any background blurring they feel might improve the result.
Also, as others have mentioned, the comparatively high-sensitivity and low-noise capabilities of modern sensors has further reduced the perceived need for a wide-aperture lens.
Consequently, there's lower demand for "artistic capability", especially in a zoom, so few are being manufactured
09-28-2022, 04:28 AM   #15
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QuoteOriginally posted by Jonathan Mac Quote
I think the "digital sensors are far better at high ISO than film ever was so there's no need for lens speed" argument has long since been debunked as nonsense. If it were true then there's be no lenses available today, prime or zoom, faster than around f/4, simply because that provides at least equal IQ as what we had in the film days. What was available at the peak of film is not any kind of established standard of what's "good enough". All else being equal, faster is always better, regardless of the qualities of sensors.

I suppose making variable-aperture zooms slower is a push from manufacturers to buy their constant-aperture zooms or fast primes but the flip-side of that is that they're offering poorer value in the variable-aperture zooms. Canon, always the first to make their products poorer value, have released APS-C kit lenses for their mirrorless mount APS-C cameras that are f/4.5-6.3. After all, why should the customer benefit from improved image quality by using a lower ISO when we can charge the same as in the past for a kit lens that's 2/3s of a stop slower than previously and keep the extra money?
The iso discussion is only one element to the equation. But you are correct in terms of offering slower (equate slower to cheaper) kit lenses in order to not only increase margins on kit lenses, which many consider throwaways eventually, but also to push for sales on the higher quality lenses. Yes this is business and money is always at the top of every decision.

The other thing to consider, is the improvements in AF performance. Since kit lenses need to work reliably at all lighting conditions the smallest aperture that value has always been one of the limiting factors as well. Although not scientific by any means, I have a long experience with pushing AF to its limits in terms of aperture. My view is that from the Z/PZ-1 through to K1 MKII the minimum aperture requirement has changed by at least one stop,
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