Can sliding apertures on zooms die? And stay dead? Please?

I've always loathed sliding apertures on zoom lenses, and I suspect I'm not the only one who feels so strongly. The reasons are obvious. Even with sophisticated metering, you're not going to get predictable, consistent exposures as you change focal length. These lenses should have died ages ago. But the cursed things live.

 

Even Leica, who really ought to know better, has several zoom lenses with sliding apertures. The 24-90mm SL, as well as the 90-280mm SL are just two. The one zoom lens for the S system, the 30-90, is an f/3.5-5.6. (But it's worth noting that Panasonic's L mount zooms will have constant apertures).

 

You might think, well, hey, isn't it better than not to have the bigger aperture at the wide end? Shouldn't we want as much light gathering capacity as we can get? Hell, no. Having a bigger aperture at the wide end gives you speed where you don't need it. The long end is where you really want speed - but you can't have it.

 

I would much prefer - and I suspect most people would agree - to have a constant f/3.5 on a zoom rather than an f/2.8-4. I'd even take a constant f/4 and have a smaller lens.

 

If you want to satisfy the cheapskates, who just want a (half-) decent camera to take on holiday, you can give them the crappy zooms. But for photographers, it should not even be an option.

 

What kind of a world do we live in when we have amazing cameras that give us more than we could hope for (e.g. A7III with 4K video, IBIS, affordable price), only to be let down where it counts - the lens? What the hell is this design philosophy? (Don't the Russians 'disappear' people who are a threat to the well-being of the nation? Can we do this with product managers, or nah?)

 

Speaking of 4K, and video capability in general, you would think that all modern zoom lenses would have constant apertures for those who want to shoot video, even if casually. Even if you accepted sliding apertures for stills, you cannot accept them for motion. There is not one Super 8mm camera (or video camera) with a sliding aperture on its zoom. If there is, I never saw one or used one.

 

And while we're at it, threaded filters can also die. There won't be any concern by the WWF about that extinction event, either.

I think it's your problem if you can get good exposure with these zoom's.

Excuse me, I am not involved with camera making but I dare to guess that in modern days sliding apertures in a system lens can be dealt with & compensated by the camera firmware & computer? If Fuji for example manage to compensate over the zoom range varying lens distortions, why shouldn't others be able to tell their camera to stop down a little further at the short end of the zoom? Do you really need to shoot adapted glass with aperture mechanically set via it's ring?

But yeah, I would not mind being able to set h-stops for externally metered work and agree that camera manufacturers seem a bit too lazy in that field for marketing's sake.

 

I don't mind threaded filters; I am actually glad to have them instead of Linhof's slide in universal ones or Cokin stuff in front of my RF glass blocking the VF.

Just put the camera in "P" mode and use exposure compensation.

I agree that if you're using a lens at maximum aperture that variable aperture zoom lenses can be a pain, but let's remember that most of these lenses are compromises that supply reasonable optical quality at a relatively low price. I only own two of these--Pentax kit lenses that I bought specifically for their light weight and low cost for use traveling or for family pictures where I don't want to carry a lot of gear. I've never had any issues with getting correct exposures with these lenses, but I will admit that I never shoot video. If you made the widest aperture at the longest focal length I suspect that there wouldn't be much savings in size and weight over a constant aperture zoom.

As for threaded filters, how else would you propose to attach them? Would we then be dealing with 5 or 6 different proprietary systems with the resulting higher costs and potential lack of choice?

It's all about cost, and how that meets the needs of the target market. A zoom lens with variable aperture costs roughly half that of a comparable lens with fixed aperture. That's not all due to optics, because better lenses usually have better build quality and materials. A kit lens in the 24-105/3.5-4 category might cost abut $600, compared to $1300 for the new Sony 24-105/4.

 

There are many variables to consider when designing a lens, such as how much correction for distortion and CA. There are additional considerations for a zoom lens, including whether the focus holds when zooming (parfocal), how much breathing occurs when the lens is focused, and whether the aperture is fixed or variable. Better performance requires more optical elements and/or more sophisticated materials, hence cost. You can get the same or better image quality at a price point if the designer allows the aperture to vary with zoom length. Another significant compromise regards linear distortion, because that can easily be corrected in firmware or post processing with minimal degradation. Likewise parfocal behavior is largely moot when combined with auto focus, at least for still photography. Variable aperture is moot when used with TTL metering.

 

Video photography is much more demanding, because of the time element. The transitions of any changes to zoom, focusing and panning (distortion) are visible, not just the start and end points.

 

If you want it all, consider lenses made specifically for video, but be prepared to walk away with a lighter wallet. Zeiss, for example, makes a line of "compact" video lenses that are nearly affordable. Prime lenses start at $5k and zoom lenses about $12K. It's not unusual for professional cinematic lenses to cost more than $100k. They are carefully designed, hand-assembled and tuned for optimal performance, and must be handled very carefully. They also tend to be large, so that focusing, aperture and zoom settings can be made remotely by a separate operator, called a "focus puller."

 

Sony makes several E-mount lenses designed for video at very reasonable prices. For full-frame cameras, there is a 28-135/4 PZ (for power zoom)) lens for about $2300. That's a real bargain for a lens with very little focus breathing, parfocal zooming and low distortion. If you want f/1.8 instead of f/4, take out a second mortgage (or rent one, like most production companies do).

I have to say that I honestly don't mind them, esp. if it means a lighter lens with similar optical quality to a bigger/heavier constant aperture lens.

 

When I was looking for a "walk-around" lens to use with full frame Nikon DSLRs(and late film cameras like the F100), I spent some time comparing two lenses-the 24-85 f/3.5-4.5, and the 24-120 f/4. The consensus seems to be that the lenses are pretty similar optically, and which is better depends on who you ask. Of course, the fixed f/4 has other advantages(a longer zoom range) but it's also a fair bit larger and heavier, and at least 2x as expensive. I bought the 24-85, and have been perfectly happy with it.

 

That's not the only variable aperture zoom I have, but it's probably the one I've used the most. I've not noticed any issues with exposure inconsistency, both with digital and with slide film.

I wonder exactly how "constant" the constant aperture zooms actually are.

Since the definition of f/ is focal length divided by (some) diameter, as the focal length increases, unless the (appropriate) diameter increases proportionally, the f/number will change.

 

Lens design is actually slightly more complicated than that, but you can't collect any more light than gets through the front lens element. That light comes from a smaller part of the object, but then has to fill the whole frame.

 

You can force the aperture to close down, but why do that?

 

In the days of external (that is, not through the lens) metering, it does simplify exposure setting. I have zoom lenses with two marks to match up the aperture number, for the two limits of zoom. Interpolate between them when needed. But with TTL metering, no need for that.

 

(snip)

 

I would much prefer - and I suspect most people would agree - to have a constant f/3.5 on a zoom rather than an f/2.8-4. I'd even take a constant f/4 and have a smaller lens.

 

(snip)

 

You mostly can't have that. If you could, they would probably build them that way.

 

As above, the amount of light is limited by the front lens element and focal length.

 

It might be that under some conditions other than the front element could be smaller, but I suspect not even that, or not by much.

 

Since tubes have to slide inside other tubes, they don't tend to change diameter much.

WYGIWYGSMTBOI !!

 

 

 

 

 

 

 

 

 

 

What you get is what you're given so make the best of it

The relative aperture is determined by the apparent diameter of the entrance pupil, as observed from the front of the lens, not the physical diameter of the disphragm. It the lens is designed so that the entrance pupil increases with focal length, by how the lens elements and diaphragm are arranged and moved when zooming, the relative aperture will remain constant. In order to do that, other design parameters must be compromised, or additional elements and/or mechanical devices, must be employed.

 

Entrance pupil - Wikipedia

I don't care for variable aperture lenses, but I do not LOATH them.

 

Besides your selfish perspective and wanting to stir the pot, did you even look at any of the reasons for a variable aperture, both engineering and business?

 

1) You are metering through the lens, so your meter is taking care of the changing max aperture of the lens.

 

2) For external and manual metering, yes I would prefer fixed aperture with an older lens with an aperture ring.

With digital, the camera is controlling the aperture, so if I select f/8, it STAYS at f/8 no mater what I zoom the lens to. It is only when I go wider than the min max aperture, that the aperture will vary. So, effectively you have what just you want, constant aperture. I used to do that all the time. Since you do not know this simple technique, I suspect you do not know what you are talking about.

 

3) For the average consumer, there is the additional cost of designing a fixed aperture lens, which does not make sense. The consumer market is more price sensitive and with TTL metering, what difference does it make? The consumer market has been, is and will always be price sensitive. That does not make them "cheapskates."

 

4) If you were Canon, and changed ALL the consumer zooms to fixed aperture, and then have to raise the price of the lenses, are you willing to give the consumer market to Nikon? I think not. If you did, you might as well close down the business.

 

And without threaded filters, how do you propose to attach a filter?

Maybe we go back to gelatin filters, and attach a holder with 3 external screws that clamp down on the lens?

Or maybe we hold the gelatin filter in front of the lens.

It seems that most variable lenses are so called "kit" lenses. As explained, they tend to cost less to produce. But that doesn't mean they are all "bad" lenses. Some of them can be very good. If the OP doesn't like the variable aperture lenses, then he can simply pay more and get fixed aperture lenses. I don't understand the whinging about it. I don't recall exposure problems with the ones I"ve had. Its not a great excuse for having bad exposures if that's your problem.

If you don't like variable maximum aperture lenses, don't use them. As others have pointed out, they're available at lower prices. The difference in cost can be huge at longer focal lengths. Given the cost of lenses reaching 400 or 500mm, I would rather have a variable maximum aperture zoom than nothing in that range at all.

 

You don't like these lenses, don't want the possibility of owing them, or to let others have that possibility. Bad luck to you with that.

The Sony 100-400/4.5-5.6 GM is anything but a kit lens, with a price tag of $2400. Why variable aperture? Probably to keep the price and weight down. It is a powerful lens, and only 3 pounds (1400 grams). Like other GM lenses, it is designed to be comfortable at 50+ MP. The 70-200/4 and f/2.8 lenses are more civilized (don't grow with zoom level), but they're not 400 mm.

 

The Sony/Zeiss 24-70/4 is not a kit lens either (pricewise and build quality), but the optics disappoint despite the constant aperture. The new Sony 24-105/4 is far better, and the 24-70/2.8 knocks the ball out of the park.

 

You have to do your homework and decide what's best for you on an individual basis.

As others have pointed out, they're available at lower prices.

Not all of them fall in that category - some are variable aperture because they could not reasonably made into constant aperture ones (because of weight, size and/or cost) - like the above mentioned Leica 24-90/2.8-4 or the Nikon DX 16-80/2.8-4; in both cases the variable aperture enables the wider-than-usual focal length range. The same goes for the 90-280, 80-400, 100-400 etc zoom lenses - no way to make those constant aperture without significant increase in cost, size and weight.

 

Until today, I have not heard of the expression "sliding aperture" being used to describe the variable aperture on zoom lenses.

 

Threaded filters - what's the problem with those? Why would everyone want to carry around a filter adapter to hold square ones? Those have advantages in some cases, as do the threaded ones in others.

Edited November 11, 2018 by Dieter Schaefer

The Sony 100-400/4.5-5.6 GM is anything but a kit lens, with a price tag of $2400. Why variable aperture? Probably to keep the price and weight down. It is a powerful lens, and only 3 pounds (1400 grams). Like other GM lenses, it is designed to be comfortable at 50+ MP. The 70-200/4 and f/2.8 lenses are more civilized (don't grow with zoom level), but they're not 400 mm.

 

The Sony/Zeiss 24-70/4 is not a kit lens either (pricewise and build quality), but the optics disappoint despite the constant aperture. The new Sony 24-105/4 is far better, and the 24-70/2.8 knocks the ball out of the park.

 

You have to do your homework and decide what's best for you on an individual basis.

 

Yes you chose two anecdotal examples that are quite pricey. That's why I said most, not all.

As mentioned above, a highly selfish perspective, and thinking most of us feel about it the same way... well, not a compliment to the crowd here.

 

I don't particalurly care for zooms of any kind, but choosing between the variable aperture 16-85VR which I had for DX Nikon, versus the fixed aperture 24-120VR I have now on FX, I'd quite like the 16-85 back. Optically it was certainly not worse, and as a landscape lens actually better. And ultimately, I care about the lens performance more than having some pristine spec sheet. And most regular posters here seem to be perfectly able to define their uses for a lens, and then buy accordingly. So variable aperture when it doesn't matter, fixed when it matters or primes if you don't need to zoom anyway. Choice is great, actually.

 

As for threaded filters - well, let's say that selfish perspective limits thinking. What alternatives? Bay1-style, which requires a thicker rim and hence is problematic with wide angles? Or hand-hold square filters, since there is no decent way to mount the filterholder onto the lens without that thread-mount?

 

There is nothing wrong with a bit of ranting or stirring the pot at times, but a minimum of thought before going off is mighty useful.

Yes you chose two anecdotal examples that are quite pricey. That's why I said most, not all.

The term, "anecdotal" applies to a response based on opinion or generalities, like "most, not all.". Giving specific examples is "evidential," and easily verified. Even price is not a consistent indicator. The Sony-Zeiss 24-70/4, in my example, is a premium lens, at $900 priced well above so-called "kit" lenses.

 

[Caution - anecdotal content] The caveat is that manufacturers, particularly third-party manufacturers, will seize on a a particular specification to promote their product. A typical ploy is extending the zoom range a few millimeters at either end. It is technically feasible to design a constant aperture zoom at a low price point by sacrificing other attributes. Zeiss does not advertise that some lenses have more distortion than their premium, Otus line, but don't bear a $5000+ price tag either. In fairness, linear distortion is easily corrected, whereas lateral CA is not, and Zeiss E-mount lenses have very low CA.

 

It hadn't occurred to me that threaded filter rings were a liability. Frankly, I would miss them. How would I attach a polarizer or "haze" filter for protection? I actually prefer bayonet filters, as on my Hasselblad lenses. They are quick to put on or remove, and secure (snap in place, push to turn). The bayonet ring doesn't seem too bulky to accommodate wide angle lenses, but for Hasselblad, 40 mm (24 mm equiv) is as wide as it gets. That lens has a threaded 93 mm ring but no filters to fit. Small format, wide angle lenses increase the diameter of the filter mount, or for some, bulge the objective so that no filter can be mounted.

As you know, the camera lens functions much like a funnel in that it gathers light based on its working diameter (aperture). That’s the good news! The bad news is --- As you zoom in, light energy playing on film or digital sensor is abridged. In other words, as you zoom to higher and higher focal length, you pay the price of reduced exposing light energy. The amount of light loss due to increasing focal length is considerable. Doubling the focal length from 50mm to 100mm results in a 4X loss. Zoom from 50mm to 200mm; the consequences are an 8 fold loss in light energy at the focal plane. In other words, the light energy arriving at the film or sensor intertwines working diameter with focal length. This is a phenomenon of physics that can’t be avoided, however it can be tamed.

 

Opticians tame this light loss via the f-number system. The f-number assignment is derived by dividing the focal length by the working diameter. The result is a ratio called the “focal ratio” (f-number for short). Thus the f-number assigned to a 50mm with a working diameter of 25mm is 50 ÷ 25 = 2 (written as f/2). Zoom to 100mm and the math is 100 ÷ 25 = 4 (written as f/4). Zoom to 200mm and the math is 200 ÷ 25 =8 (written as f/8). This is the basis for the unavoidable light loss with the zoom.

 

As I said above, the light loss is unavoidable. This is true, but we can find work-arounds. Suppose you make the lens larger in diameter and then mechanically link the working diameter of the aperture of the iris to the zoom mechanism. One could evade the light loss this way. Sounds good, but likely impractical -- thus too complicated and too expensive.

 

Alas – how to avoid the devastating light loss? Opticians must use multiple lens elements to mitigate the seven foremost lens aberrations that plague us. This can be accomplished by constructing the lens using a minimum of seven individual lens elements. To handle the light loss of the zoom, the front lens group is fashioned to magnify the iris. In other words, the diameter of the iris appears larger or smaller than reality with the zoom. Thus the outside world sees a varying aperture diameter. This actually works! The degree of magnification changes with the zoom, and this action results in a constant f-number throughout the zoom.

 

Well, maybe! To make this work, the front elements of the zoom lens must be quite large to begin with. This is not cheap because the larger the lens diameter the more the aberrations. This is because light that enters the lens at the margins must be refracted (bent inward) to a greater extent.

 

The bottom line, making a constant aperture zoom lens is not easy and adds to the selling price. Now the lens maker must juggle the selling price against production cost. Sometimes you get the bear and sometimes the bear gets you!

In days of old (manual film cameras), a variable aperture zoom was a PITA if used at maximum aperture, because it required the user to adjust the shutter speed as the lens was zoomed out. In an automatic exposure film camera, it is only a concern if used in M mode at max aperture, but not much of an issue in any of the auto exposure settings. In a digital camera with an auto ISO function, it is really not a significant operational issue when used in any TTL exposure mode. I prefer constant aperture zooms, but given cost, size, & weight constraints, I have no issue using a good variable aperture zoom for digital imaging.

I get it Ed, its both evidentiary, in other words yes those high quality variable lenses exist and are not considered "kit" lenses. It's anecdotal because a couple of examples of high end kit lenses doesn't represent anywhere near the whole field of those types lenses. Basically, because they are less expensive to make and lighter, and producers tend to use more plastic in their construction, many producers present them as a "kit" lens to be sold with a body as part of a package. This also doesn't mean plastic lenses are bad lenses either, just cheaper to make. BTW that Hasselblad 40 mm, if its the same model I've used before, is an amazing lens, but the front is so wide it would take a huge filter. I've never seen one with a filter.

Just put the camera in "P" mode and use exposure compensation.

You what, guv?

 

As for threaded filters, how else would you propose to attach them? Would we then be dealing with 5 or 6 different proprietary systems with the resulting higher costs and potential lack of choice?

The same idea as for mounting lenses. Threaded mounts are all gone. But that change never happened for filters, alas.

 

But with TTL metering, no need for that.

 

1) You are metering through the lens, so your meter is taking care of the changing max aperture of the lens.

It doesn't always work that way. Sometimes you can't take a new reading after zooming, for whatever reason. Sometimes the only way to take a reading is to either use an incident meter or the LCD, and having to compensate after zooming is troublesome.

 

so if I select f/8, it STAYS at f/8 no mater what I zoom the lens to. It is only when I go wider than the min max aperture, that the aperture will vary. So, effectively you have what just you want, constant aperture. I used to do that all the time. Since you do not know this simple technique, I suspect you do not know what you are talking about.

Except that the smallest aperture at the wide end can be, say, f/22, while at the long end it can be f/36. Perhaps not a massive deal, but yes, I do know what I'm talking about. But I don't want to be unfair to people such as yourself. Not all photographers have extensive technical knowledge, and many don't care. To each his own!

 

3) For the average consumer

The average consumer is probably very happy with their dual-lens smartphone. Should they be? It's up to them.

 

And without threaded filters, how do you propose to attach a filter?

Maybe we go back to gelatin filters, and attach a holder with 3 external screws that clamp down on the lens?

Or maybe we hold the gelatin filter in front of the lens.

Oh, Gary, Gary, Gary.

 

As others have pointed out, they're available at lower prices.

The lens I use the most is a constant aperture tele zoom (not going to give that away, as it's my super secret lens of intrigue, which is something very different from state sponsored life insurance). It's cheaper than the sliding aperture kit lens that came with my camera. I have another tele zoom with a constant aperture, and it is a bit more expensive, but worth about the same as that kit lens. Caveat: they are both manual focus.

 

Until today, I have not heard of the expression "sliding aperture" being used to describe the variable aperture on zoom lenses.

All lenses except catadioptric (mirror) lenses have variable apertures. For the most part. Smartphone lenses don't, for example. But there is a difference between 'variable' and 'sliding'.

 

The other flaw with most zooms is that they are varifocal, instead of parfocal. That means that you have to refocus after zooming. Not a good thing, but AF does take away most of the sting, if you use AF (though I wouldn't know). But, unlike with constant apertures, making a lens parfocal seems to be more involved and therefore much more expensive. That is to the best of my knowledge.

 

Would we then be dealing with 5 or 6 different proprietary systems with the resulting higher costs and potential lack of choice?

Let's remind ourselves of how many filter sizes there are!

The same idea as for mounting lenses. Threaded mounts are all gone. But that change never happened for filters, alas.

 

Bayonet mounts for filters were once reasonably common, but are now a thing of the past. I don't think there are any current lenses that use them, and if filters are still made they're likely expensive and very specialized.

 

I have a camera system that uses nothing but Bayonet 50 sized filters(aside from on particular wide angle lens, which uses Series VIII filters). Yes, they're convenient, but most often I use Bay-50 to 55mm threaded adapter.

 

Round threaded filters are terrible if you need a grad ND, but they work pretty darn well for everything else.

 

BTW, there's a fair bit less involved in making threaded filters than threaded lens mounts. M39(LTM) includes the rangefinder coupling lug, while M42 has the lens stop-down pin. LTM lenses tend to be fairly light, while M42 lenses can be somewhat heavy and bulky, and the mount has to support that. The same is NOT true of filters.

 

Also, let's not forget that the "variable aperture" phenomenon isn't restricted to zoom lenses. All lenses have some light loss as you move away from infinity, although in 35mm format cameras it's usually not all that significant until to you start getting into the 1/2 lifesize range.

 

All of that aside, my electronic Nikons, both film and digital, correctly compensate for light lost in variable maximum aperture zooms and in macro lenses at close focusing distances. If I set a lens to f/5.6, for example, the camera is "smart" enough to hold it at a f/5.6 regardless of where the zoom ring is set or how closely I'm focusing.