A common question people have about lenses is whether extending lens barrels are worse than fully sealed internally zooming/focusing lenses.
There are two lens actions that can cause the lens barrel to move in and out. Those actions are focusing and zooming. Some prime lenses will have a moving front element and that will cause the lens barrel to move in and out during focusing. On the other hand, many zoom lenses will have lens barrels that move in and out during zooming.
Many people rightly assume that extending lenses are inferior but they aren’t inferior in every single way!
Here are 2 advantages of extending zooms
Advantage #1, the lens can be collapsed and fit into a smaller space for transportation. With moving lens barrels the lens changes size so that the lens can be fully zoomed in or out to make the lens as small as possible. This makes fitting the lens in a camera bag a lot easier.
Advantage #2, lighter overall weight and better balanced. The thing I hated most about fully internally zooming 70-200’s was how front heavy they were. After hours of shooting at a wedding it really starts to feel heavy. The new RF 70-200mm f/2.8 which has an extending barrel zoom design is much easier to handle by comparison.
Here are 2 disadvantages of extending zooms
Disadvantage #1, the lens size and thus overall balance can change drastically. In some cases, such as balancing a camera on a gimbal, zooming the lens in and out can cause the gimbal to go out of balance if the lens extends too far.
Disadvantage #2, potential for dust to enter the lens. Modern lenses are usually sealed against dust but, it only reduces dust in the lens, it does not prevent it 100%. This could be due to the vaccum effect of the moving front element. Essentially, the lens must suck air inside of it when the front element extends because extending the lens increases the internal volume of the lens. This can cause dust and moisture to be pulled into the lens when zooming in and out.
There’s no avoiding the fact that all internal focusing and zooming is the best solution if you’re going to be going near water spray or big clouds of dust and sand. That is probably why most companies make fully sealed all internal focus and zooming telephoto lenses for professional use.
Is dust inside the lens really that bad?
Some small dust specs inside the lens will have no noticeable effect for telephotos typically. It can be a lot worse for wide and ultra-wide angle lenses because the depth of field they have might bring the dust into focus which will cause little shadows to appear in the final image.
Most of the time dust won’t do much for any kind of lens unless the sun or another really bright light is in the frame. In that situation some reflections can occur off the dust that become visible.
In normal lighting the dust is usually blurred out so much that it isn’t visible in the final picture.
What should you do if dust gets in your lens?
If your lens does get a lot of dust on the inside you can send it in to the manufacturer and they will clean it if it is under warranty. If it is not under warranty anymore you will have to pay for it to be cleaned. Ask the company that made your lens what they charge for a lens cleaning.
If you expect the company to clean your lens you should have example photos showing that the dust affected some photos, otherwise they probably won’t clean it.
4 Comments
What about the Price? Mirror less, DSLRS cameras will cost you hundreds for lenses plus the camera thousands, then you have to carry a huge camera bag everywhere. Many places will not allow to film with a huge camera and lenses
Now the new Sony 70200GMII is more lighter than Canon RF70200 being an internal focusing lens. And I also think it doesn’t looks good when Dust goes inside and appear from outside of the lens in front element. Somehow i like the lenses to be with internal focusing.
The Canon RF 70-200mm f/2.8 L is also an internally focusing design with dual focus groups. The zooming part is external which allows it to collapse in size.
I guess it is down to preference, I own only one internal zoom lens the EF 70-200 IS l f2.8 USM ll all other lenses I own are external zoom. I have made the transition from DSLR to mirrorless, and sold to help finance my transition. I would not sell my 70-200 for the simple reason there is less chance of dust getting into the elements. Size is obviously a consideration, as is weight.
I personally am used to the weight/size of the internal zoom lens and do not mind extending it slightly with a mount adaptor, I baulk at paying the price of the new 70-200 f2.8 with external zoom. I am worried that at events I attend Motor X for example where there is a lot of dust kicked up from the riders, and being close to trackside that any specks of dust will be sucked into the lens, on the action of zooming.
We are all individuals and debates in the camera world have raged there are the crop sensor die hards full frame die hards, so I guess this will rage on.