R.G. Loc: Scotland

I haven't been able to find any info on this subject online so I have been left to speculate. I was hoping to get some feedback here.

Most compacts and some interchangeable lenses have rectangular lens masks as shown below. I'm assuming that their purpose is to eliminate any surplus light from entering the lens so there will be less stray light bouncing around inside the lens, giving better contrast and truer colours. Is that right?

Are the advantages marginal? I would assume that if the advantages were more than marginal we would see them used more frequently. Has anybody experimented with their own lens masks using something like cardboard, tape or Haagen-Dazs ice cream tub lids? Can they be used on any lens or is there something preventing them being used on some types of lens? I assume that with a zoom lens the size of the opening would have to be chosen to accommodate the shortest focal length (i.e. the widest zoom).

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Image found online.

speters Loc: Grangeville/Idaho

Well, they haven't made any round sensors yet, so a rectangular mask is one that makes sense!

drklrd Loc: Cincinnati Ohio

If that were the case I think all major cameras like the Nikon pro and sub pro cameras as well as the Canon versions would all have this applied to them and all of their lenses. I still own all of the special effect masking devices I used back in film days. I have found that these masks and other special effects can be used the same way on digital lenses. I used to ask myself why they did what you speak of to the cheaper cameras and the only answer i could come up with is that the cheap plastic lenses they use on these lower ranking cameras probably need some sort of masking on the lens because they do not use the correct amount inside the camera. They also use the cheapest lenses they can as manufacturers always did do when masking the lesser expensive versions of cameras. Check out an old Kodak Brownie it I think has only a front lens with no other element behind it. I know the old box camera I have is that way. The old box camera and the old Brownie were cheap versions of cameras that worked fine for the novice. just like the camera you have shown works fine for the novice. A good beginner camera if nothing else. Just do not expect it to be more than it is. I went past the beginning stage many years ago. I still shoot as a pro so I use at least semi-pro gear and maybe I will get a Nikon D850 this year by Christmas, depends on how much cash I accumulate by then. As I said if there were advantages they would have had them on the pro-line cameras a long time ago even back in film days. I have seen a few beginner 35mm film cameras with this design.

R.G. Loc: Scotland

I'm assuming the reason to use a mask as opposed to the usual lens hood is that the mask will reduce the incident light to the absolute minimum, and in so doing it will reduce stray light within the lens/camera to a minimum. I'm also assuming that it's more than just an anti-flare technique and that it will improve image quality.

R.G. Loc: Scotland

You may have a valid point when you note that it's stuff at the cheap end that usually has that kind of mask. Perhaps higher end lenses have internal masking. Whatever the internals are like, I can see the advantage in reducing stray light within the lens.

Hamltnblue Loc: Springfield PA

I think with point and shoots it accommodates the lense protector when shut off

R.G. Loc: Scotland

Hmmmm. That may also be a valid point. However.... I looked for a shot of a Sony RX100 with a closed lens front and couldn't see one, so I'm assuming that they have the mask but it's not to house a lens protector. The RX100 series would be an interesting example to consider because they definitely aren't at the cheap end of the market.

SpyderJan Loc: New Smyrna Beach. FL

I would guess that since those entry level cameras don't have the provision for attaching lens hoods, the mask does that job.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

As long as I do not point my point in shoot into the sun I have no need of any type of supplemental ice cream containers.

drklrd Loc: Cincinnati Ohio

Actually a really good lens for a camera does not need masking at the film plane or sensor end . The lens actually focuses the light, though the lens is round, into a rectangular area onto to the sensor or film plane. They are made round to accumulate as much light as possible and to ease the use and application of focus and iris (old film days before film planes evolved) as well as eventually the design of telephoto lenses. Much easier to turn a round lens than turn a square lens on it circular axis. They just made the lens focus to a square or rectangular image to fit the film plane and eventually the sensors of cameras. I think all photographers could use a lesson in optics as it would enhance their use of lenses. I studied all of this in high school when I wanted to be a photographer and was president of the camera club. Their darkroom became my hiding place from the teachers and classes I did not want to be in especially those damned study halls.

R.G. Loc: Scotland

If the lens can do that without creating any stray light then I can see that it wouldn't need any masking - either internal or external. Perhaps the most effective use of such masks is as an alternative to the usual type of lens hood (which definitely plays a role in suppressing lens flare). I wonder if the internal flare problem of the Nikon D750 would respond to the use of a rectangular mask. I also wonder how completely the lens manufacturers manage to suppress stray light within the lens/camera.

Thanks for your comments and continued input.

R.G. Loc: Scotland

That is undoubtedly a valid point, SpyderJan. Thanks for your comment. I'm coming to the conclusion that such masks are an alternative to conventional lens hoods.

R.G. Loc: Scotland

Amongst the very limited info that I found online was someone who had some success experimenting with various mask-making techniques. Apparently it's a recognised fact that a certain lens size (unstated in the article) provides a perfect mount for Haagen-Dazs tub lids (which can be turned into various types of masks - for example masks used to create shaped bokeh). Unfortunately that article didn't provide any details about what a rectangular mask would achieve. I was hoping to get further details by asking in UHH.

drklrd Loc: Cincinnati Ohio

In film days using the Monte Zucker kit was the more expensive route than an Ice cream container lid as was using a bellows assembly with cutouts in the front slots. I used to do multiple exposures with masking in front of the lens. Looked as good as you can do it in Adobe these days. You used a one half mask in front of the lens for part of the exposure and then reverse the mask for the other half of the shot. there was also the use of the film slide for a similar purpose as the film slide half way out gave you one half a negative that you could then match up with another half negative shot. Some masks I made by hand but most because I used them at weddings were purchased or loaned by a studio when the customer wanted something only that studio did and I did not have the mask to do it with. We as photographers using film were much more ingenious than todays photographers seem to be. We did it with film which is a one shot medium and we could duplicate the shot every time. Like the pic of the bride in wedding gown in the mirror while still in blue jeans looking into the mirror. A double exposure shot done on scene at the wedding. You had to have 2 cameras because one would be left with the tripod and locked down tight until you came back for the second exposure. You then used the second camera to keep shooting as in the grooms shots while you waited for the bride and party to dress to get the second shot. Trust me you had to keep pace with the action and activity so as not to become a burden on the brides schedule. It was termed "in camera masking" back then and can still be done in digital if you can turn your digital into a full manual camera.

R.G. Loc: Scotland

Thanks for the fascinating description of in camera masking. Clever things can be done in PP, but it doesn't seem as ingenious as doing things on the hoof in real time and under time restraints.

Since masks are a part of photography's history, you must be right when you say they're not needed in well designed optics, because if there was an obvious advantage in using them it wouldn't be difficult to implement them on every lens.