do wide-angle lenses really stop action better

[Luke]

I was just reading on another camera forum that wide angle lenses don't need to be as fast to stop action as longer FL. I'll admit that there is a lot about photography I don't understand, but I just DON'T understand it. I mean 1/125 of a second should be the same regardless of AOV......no?
Can someone explain how this works to me, or is this just a bunch of people blowing hot air?

So you can understand my confusion, it starts in this thread in post #20 ....... http://www.pentaxforums.com/forums/pentax-beginners-corner-q/188577-good-fast-lens-budget-2.html

 

[HeatherTheVet]

I'm waaay behind you. I don't even understand the question.

 

[bartjeej]

at a given distance, if a subject moves, for instance, 1cm during the time of your exposure, that movement will cover twice as large a part of your image if you shot it at 100mm, as compared to shooting it at 50mm, simply because at 50mm there's twice as much scenery in you image, so 1cm isn't such a big deal anymore. In other words, because the subject occupies a smaller part of your frame at wide angle, the subject blur also occupies fewer pixels, giving an impression of more sharpness.

 

[Landshark]

"wider focal lengths have thicker DOF, so a moving target is more likely to be in focus.

From PentaxForums.com: http://www.pentaxforums.com/forums/pentax-beginners-corner-q/188577-good-fast-lens-budget-2.html#ixzz1ztAMhAiT"
this would be the only reason F 2 on a 24 will have more than on a 85, so it will not stop the action any more, it just will give you a better chance of being in focus.
Also wide angles tend to focus quicker because their lens movement is less, therefore quicker.

but you are right other than stopping action with high speed strobes shutter speed is the only way

 

[Isoterica]

They both said it very well. I'll just add one more visual to it.

If you were shooting a flower with a 100mm macro, just the slightest shudder from a car going by outside of your house [have had it happen] could make the subject move a millimeter between the time you hit your remote and the image is captured. Even with mirror lock. That's because you are focusing on something really tight with a long lens. It takes longer for the light to get down that longer lens, apertures being equal. The result-- your subject can end up blurred or even out of frame. Now shoot something with a wide angle lens, say a bike rider with 35mm. Depending on your proximity to him, you've got room to lead him and even though he is moving [you might be panning after him/or not], you have a wider frame to capture him in. More light gets to the sensor faster because of the shorter lens length [remember apertures being equal].

100mm at 2.8 vs 35mm at 2.8, same subject, a man riding a bike, same distance.. the wider lens will have a better chance of capturing the man amd.. more clearly. Shutter speed and iso will raise your chances of stop action. Or as Bob said, some kind of strobe or flash.

 

[Ripleysbaby]

It would be interesting to know the exact time difference of light traveling down various focal length lenses ! I suspect there would be more than a few digits ,post decimal point .
Or am I reading the last post wrong.

 

[bartjeej]

uhm... with light travelling at 300.000 kilometres a second, the difference between for instance 25mm and 50mm would be the difference between 1/12billionth of a second and 1/6billionth of a second... not the sort of difference you can really pick up in a camera, I think (well, except that one REALLY cool camera that MIT made a while ago). I think the deeper DOF thing is also something to consider but doesn't strictly speaking stop down the action better, as Bob also said.

Having read the pentax forums thread, I think the wide angle / smaller subject size / smaller blur size thing is pretty much what he's talking about (or at least, that's the only valid explanation I can think of for his statements). If the subject distance remains equal, and your lens is twice as wide, the subject is twice as small so any motion blur will be twice as small too, making it less noticeable (or even making it disappear, if it's small enough). So for the longer lens to have equally low (visible) motion blur, it would need twice the shutter speed, requiring twice as fast an aperture (or twice as high an ISO value). That's why he's saying a 24/2.0 is equal in motion stopping power to a 50/1.0.

 

[Luke]

Thanks bartjeej..... in your first post, it all seems logical enough. I just don't think that in practice that I believe it. And I appreciate the point Bob makes about in focus and oof area because of DOF, but I'm talking about motion blur.

It's that bit about a 24/2.0 being equal in motion stopping power to a 50/1.0 that makes my head swim.

 

[BrianS]

If you enlarge the main subject in the image taken with the wide-angle lens and telephoto lens at the same shutter speed to the same size then the blur will be the same.

If you want a picture of a football field, soccer field, baseball field, etc- wide-angle lenses can be used at slower speeds. But if you enlarge images of individual players, go with a telephoto.

 

[Luke]

Brian, thanks for putting it in those terms....that's what I thought. Movement is movement. I'll stick with the facts. I just can't understand why there are so many fast 50s (faster than f2), but in wider angle lenses (I'm looking for something that is around a 35mm equivalent), there's nothing that fast.... or they are prohibitively expensive. I thought maybe this was the reason....maybe they didn't NEED to be as fast. But it appears this is not the case.

 

[bartjeej]

If you enlarge the main subject in the image taken with the wide-angle lens and telephoto lens at the same shutter speed to the same size then the blur will be the same.

If you want a picture of a football field, soccer field, baseball field, etc- wide-angle lenses can be used at slower speeds. But if you enlarge images of individual players, go with a telephoto.

You're right in that, relative to the subject, the blur will be the same for both wide angle and tele (for instance, for a 4 metre long car that moves 4cm during the exposure time, the blur will always be 1% of the car). However, if you photographed that car (from the same distance) with a tele lens so that the car fills the frame, those 4cm of movement will be easily visible, because it'll cover about 4% of the entire frame. If you shot the entire street using a wide angle lens, the car's movement will likely not even be visible because the car is so small in the frame, that 4cm of movement is hardly worth a single pixel.

[edit] regarding the lack of fast wide angles, I think that's mainly because the wider the lens, the more difficult it is to keep corner sharpness at an acceptable level, which ofcourse is made even more difficult if you have a wide aperture.

 

[Isoterica]

I think everyone's got the idea. Manufacturers and people sponsored by said manufacturers use certain key words to sell their products. That carries to the general public and the public can make for great, free advertising. They just don't always know what they are singing about. Luke's Spidey sense was tingling regarding 'hot air' and he was right to question. In the end it comes down to what length you want to shoot. If you need a 24mm length then a 50 won't give you a 25mm view.

There was a nice little table on this sight explaining light-gathering at various apertures. I just thought I'd share. It's about 2/3's down this page: Understanding Camera Lenses

 

[Ray Sachs]

Isn't there also the question of how much light a lens will naturally gather at its focal length? Wide angles are drawing light from a much larger area than a telephoto, so are inclined to shoot the same scene (not really the same scene at all, but shooting from the same spot in the same direction) at a faster shutter speed than a telephoto, all else (aperture and ISO) being equal. So that's another way that a wide angle is more apt to stop action and result in less motion blur for a given scene. Also, while its true that if you cropped a wide angle to the same scene as a telephoto at the same shutter speed, you should see the same amount of blur, that's not how you'd actually SHOOT a wide angle. So I think its still a very valid point that wide angles can get by without image stabilization in situations where longer lenses would struggle. I think in a strictly technical sense, Luke is right that a given subject at a given shutter speed should be equally "frozen" by the camera regardless of focal length, in the real world of how we use wide angle vs neutral vs telephoto lenses, its still generally true that the wider the lens, the easier it is to freeze action.

-Ray

 

[Luke]

Thanks for adding that Ray. I understand what you are saying about a wider angle lens letting in more light (I understand it theoretically), but does it truly work that way? If I shoot a static evenly lit scene with 2 different lenses using the same ISO, shutter speed and aperture, is the wider lens overexposed compared to the other one?

 

[Ray Sachs]

Take a zoom lens, put it at the long end at its widest aperture. Then zoom it back to the wide end, maintaining the same aperture. Look at what happens to the shutter speed. You can sometimes fool this if a particularly bright part of the scene is what you're zoomed in on at the long end and you can exaggerate it if the wide scene includes some bright areas not included in the zoomed in scene. But if its a pretty evenly lit scene, the shutter speed will be faster at the wide end than the long end.

-Ray

 

[Isoterica]

Thanks for adding that Ray. I understand what you are saying about a wider angle lens letting in more light (I understand it theoretically), but does it truly work that way? If I shoot a static evenly lit scene with 2 different lenses using the same ISO, shutter speed and aperture, is the wider lens overexposed compared to the other one?

Since you thanked on that link I added I trust that you read how much light can enter lenses at various f-stops.

If your exposure triangle is the same, the ISO, Shutter and Aperture.. then the wider lens results should not differ from the longer lens results other than of course the composition will have changed, you will have more of the scene in frame or less. The deal with wider lenses is, I believe, is in the way they are constructed that allows the mfg's to give them 1.4, 1.2, 1.0 and those f-stops as opposed to 2.0, 3.5, 5.6 etc.. will let more light in if wide open. But if all things are equal then the only difference should be your focal length.

You can shoot with an f-stop of 5.6 in the evening but you will need a tripod or some kind of added light via strobe or flash. You can more likely shoot at an f-stop of 1.0 in the evening, hand held. *Not always. Also that 1.0 mid-day.. would need to be stopped down in many cases [meaning not wide open at 1.0] or you will get over exposure. Again it's about the aperture in relation to the iso and shutter speed, not the focal length of the lens.

My little extra: If you do something like stacking, a teleconverter, an extension tube, a macro lens.. chances are you will need to add light. You could shoot on bulb but your target area of focus would be so tiny, the chances of it remaining still through a minute of exposure time is probably not going to happen. So you would add ring flash or other kinds of light. But again that is a tiny, tiny subject, not shooting landscape or street and light would be to compensate for shutter time and ISO.. you don't want grain and you don't want your shutter open too long or you will get blur.

 

[bartjeej]

^ correct, equal ISO and f-stop will require an equal shutter speed for both wide angle and tele lenses. Things change if you're talking about physical aperture size (since a 10mm aperture would be f/2.5 on a 25mm lens but it'd be f/5 on a 50mm lens), but the reason f-stops are used is exactly that you can use them regardless of focal length, where exposure is concerned. For DOF, it's the physical aperture size that's important.

 

[Adam Quek]

Light measurement is an arithmetic thing. So theoretically the faster the lense, the higher the shutter speed you could afford to use for the same scene on the same spot metered, be it a 12mm or 500mm.

However, a wider lens have a relatively bigger DOF than a telephoto lens, due to the pure limitation of light travelling within the tube (Understanding Depth of Field in Photography does a better job at explaining the technical mumbo-jumbo). So assuming that the user is using an average or smart meter (it's still average metering!), the lux measurement for the longer lens would tend to be a tad lower than that of the wider lens, resulting to the requirement of half a stop difference to compensate for the exposure. This could potentially cause the shutter speed to be slower for the telephoto lens as compared to the wider lens, on the same scene and the same stop.

No idea if the comment stems from this inconsistency in light metering.