Fung Wei Liang
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650mm f2 @ $1000. Too good to be true?
- Thread starter Fung Wei Liang
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Fung Wei Liang
New member
I did a test, with a standard zoom lens and telephoto prime lens. For the standard zoom lens, I used the 3x digital zoom to have almost the same focal length as the telephoto prime lens. I have taken a frame each from both video. Can you guess picture 1 or 2 is the one with 3x digital crop?
Pic 1: http://www.flickr.com/photos/28643266@N02/6127837372/
Pic 2: http://www.flickr.com/photos/28643266@N02/6127846284/
Pic 1: http://www.flickr.com/photos/28643266@N02/6127837372/
Pic 2: http://www.flickr.com/photos/28643266@N02/6127846284/
thisisapocalypse
Well-known member
You'll get the same FOV as a 650mm lens on FF35 with the 3x crop in video mode, and yes it will have the light-gathering power of an f/2 lens, but the resulting image won't look anything like what a real 650mm f/2 lens (if such a lens existed) that covered FF35 would look like aside from FOV.
A 135mm is always a 135mm lens, always, and will retain the characteristics of a 135 design, it won't have the compression of a 650mm nor the look of a 650mm f/2. While you will have the light-gathering power of f/2 at 650mm, you will not have the DOF of a 650mm lens at f/2 on FF35 -- you'll have f/2 x 1.6 x 3 = 9.6.
So, you'll have a FOV of a 650mm lens on FF35 with DOF as if the lens were set at about F/10, the lens characteristics of a 135mm f/2, and f/2 light-gathering power -- useful for video? Sure. Will it look anything in the world like what a 650/2 on FF35 would look like? Not even close, not even on the same planet, not even in the same galaxy, maybe not even the same universe.
Just take a photo in stills mode with a 135/2 and then cut out a 1920x1080 image -- that's what you are working with, the difference between what that looks like and what a full image from a 650/2 lens would look like are hardly comparable.
Don't mean to shoot you down -- these modes are certainly useful but lenses are a lot like car engines, the only substitute for cubic inches is cubic *money* -- there's just no way to work around that.
Ryan Patrick O'Hara
Veteran
That example you provided wasn't optimal. Taking a photo, of a photo, makes it hard to decipher which characteristics were from your camera or the original camera. <br><br>And why are you referencing FF photography? If anything, talk about the 3x... but forget about the 1.6x... useless in the equation since we're not talking about FF FoV.
You are simply using a 135mm lens with 3x smaller sensor area extraction of HD image.
You are still using a 135mm but with the FoV equivalent of a longer lens.
So yes... too good to be true.
You are simply using a 135mm lens with 3x smaller sensor area extraction of HD image.
You are still using a 135mm but with the FoV equivalent of a longer lens.
So yes... too good to be true.
It depends on which characteristics of a 650/2 you're looking for. In terms of reach and light gathering ability - which I would consider to be the two most important factors for a telephoto, you do get a 650/2. Just have to understand that you will get a image quality hit. IOW, it's a pretty good survelliance lens.
In terms of DOF, it's a 135/2.
In terms of DOF, it's a 135/2.
thisisapocalypse
Well-known member
You're correct that we could throw out the 1.6x and just say we're starting with a 135mm lens on an APS-C sized-sensor, but since the OP is referencing a taking-lens that was designed to create an image circle for FF35 it makes sense to talk in those terms just to keep everything straight and most 600mm or longer lenses are designed for FF35, so it's a reference point that most people understand.
Plus the OP was clearly thinking in FF35 terms given his math and the subject of this thread, and he seemed genuinely interested in whether or not with the digital crop factor he could have a pocket-sized-superfast-telephoto along the lines of one of the big white monsters (although with a focal length and speed more aggressive than anything Canon makes) but in miniature. It seemed to me that his question was really about whether or not with this crop factor if he'd be getting the same kind of image that he would with a really big lens on a regular FF35mm stills camera.
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thisisapocalypse
Well-known member
It would definitely be a good surveillance lens, but I think it'd be otherwise a fairly boring looking image, whereas a real 600mm f/2 lens @f/2 on a FF35 or even an APS-C sized sensor would be breathtaking...both in terms how it would render an image as well as what it would do to your respiratory system as you carried it around.
This is incorrect. Sensor size affects DOF. Yes, the DOF is what it always be for a 135mm f/2 lens on the sensor size you are using, but once you start doing conversions and talking in terms of FOV equivalents of another format you need to apply the same math when talking about DOF to keep all the terminology consistent.
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vision_filmz
Carbonite Member
What advantage in your opinion is that a longer lens would bring? Also what exactly is compression when talking about focal lengths? So you are telling me that a 50mm and an 85mm lens will make an image look different even if you compensated for the distance?
It's about how the background looks in relation to the subject. With a wide lens, the background will look distant. With a long lens, the background will appear a bit closer. Think about the old "zolly" move, used in Hitchcock's "Vertigo" (and just about every horror/b-movie and teen comedy in the 1980s). The camera will dolly in while zooming out, or dolly out while zooming in. That's a great way to see image compression in action, as the background stretches or compresses as the camera makes its move.
vision_filmz
Carbonite Member
So why do most people favor using a lens such as a 100mm+ for a zoom up as opposed to using a 50mm and walking closer? I mean does it really look that much better?
HansSteinert
Well-known member
Depends on the look you want. Generally, the compressed Z-axis of a telephoto lens will flatter the face more because the nose, ears, and various other aspects don't stick out anywhere near as much. I love a telephoto look for close up face shots, personally. Especially if the subject is an attractive female.
thisisapocalypse
Well-known member
It all depends on what you are trying to achieve.
Portrait lenses tend to be called such because the 85-135mm focal length range renders the image with a kind of compression that tends to be aesthetically pleasing for human faces.
So, even if you compensated for distance, or cropped in on a wider lens, you wouldn't benefit from the compression inherent in telephoto designs (generally considered 85mm and above.) So no, if you shoot the same image with a 35, 50, 85, and a 135 - even if you compensated for distance either by moving yourself physically or by cropping so that you'd maintain consistent FOV across all the shots, the resulting images would not be identical. Only FOV would be similar.
Now whether or not this is "better" is relative and depends on your aesthetic. Some photographers like to use wides/standard lenses and get up close and personal with their subjects as opposed to using a telephoto lens -- by doing this you do tend to create a more "immediate" feel with the subject -- and that can be just, if not more beautiful than the compression of a telephoto lens, it really depends on the photographer, the subject and the feeling the photographer wishes to convey to the audience, there's no "right" or "wrong" way or "better" way, just different ways of approaching a subject and your approach (which includes lensing decisions) should be made with all the above in mind. Rules can be broken all the time, but there are some generally accepted practices that tend to work well most of the time for certain kinds of projects -- using a nice 85-135mm fast prime wide-open tends to create a very flattering look for portraits (especially on female subjects) and this look can't really be achieved by going wide/cropping or getting closer.
Someone who does their close-ups with very wide angles often is Wes Anderson (I think Yeoman is usually his DP) and this works perfectly for his manner of storytelling -- you need to be up close and personal with his subjects, if you swapped out his shots of this sort with shots done on something like a 100mm you'd lose the imperfection that a 20mm lens magnifies, the shots would feel distant and you'd lose a bit of connection with the characters, so again there is no one right answer, only the right answer for your particular work and subject.
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Samuel H
Major Contributor
when using a 135mm f/2 on a 600D with 3x crop mode:
* FoV and light gathering will be those of a 650mm f/2 on a 5D2
* DoF will be that of a 650mm f/9.6 on a 5D2
* sharpness will be much worse than that of a 650mm on a 5D2
* compression will be that of a 650mm on a 5D2, because it only depends on FoV
@sharpness: 2 causes for loss of sharpness: first, you're using a bayer pattern of 2K or less to get a 2K image, and that means you'll get a soft image; and second, by enlarging the central portion of the full-sensor image, you're expanding 3x the sharpness issues that your lens has
@compression: all that matters here is perspective
consider a close-up shot of a guy, with another guy in the background, 5m behind the first guy
first, you're using a 5D2; if you shoot from 1m with a 35mm lens, you'll get the close-up of the first guy, and the guy in the background will look tiny; if you shoot from 18m with a 650mm, the first guy will be just as big as in the first shot, but the guy in the background will be much bigger; in fact, he'll look nearly as big as the guy in the foreground
now, if you shoot with a 135mm on a 600D with 3x crop mode... you have to be 18m from your foreground subject, and perspective will be exactly the same as with the 650mm on the 5D2, and the guy in the background will look just as big
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@light gathering: if we ever get a camera that samples your 1080p video from the whole sensor, and offers this 3x crop mode too, my guess is that, while light gathering by the lens will remain the same (because the lens doesn't change), the 650mm lens will be much better for low light, because you'll get much lower workable ISOs with the 3x crop mode (you lose the advantage of subsampling, which averages noise out) (with current line-skipping, there's no averaging-out of noise, so this just something we may find in the future)
* FoV and light gathering will be those of a 650mm f/2 on a 5D2
* DoF will be that of a 650mm f/9.6 on a 5D2
* sharpness will be much worse than that of a 650mm on a 5D2
* compression will be that of a 650mm on a 5D2, because it only depends on FoV
@sharpness: 2 causes for loss of sharpness: first, you're using a bayer pattern of 2K or less to get a 2K image, and that means you'll get a soft image; and second, by enlarging the central portion of the full-sensor image, you're expanding 3x the sharpness issues that your lens has
@compression: all that matters here is perspective
consider a close-up shot of a guy, with another guy in the background, 5m behind the first guy
first, you're using a 5D2; if you shoot from 1m with a 35mm lens, you'll get the close-up of the first guy, and the guy in the background will look tiny; if you shoot from 18m with a 650mm, the first guy will be just as big as in the first shot, but the guy in the background will be much bigger; in fact, he'll look nearly as big as the guy in the foreground
now, if you shoot with a 135mm on a 600D with 3x crop mode... you have to be 18m from your foreground subject, and perspective will be exactly the same as with the 650mm on the 5D2, and the guy in the background will look just as big
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@light gathering: if we ever get a camera that samples your 1080p video from the whole sensor, and offers this 3x crop mode too, my guess is that, while light gathering by the lens will remain the same (because the lens doesn't change), the 650mm lens will be much better for low light, because you'll get much lower workable ISOs with the 3x crop mode (you lose the advantage of subsampling, which averages noise out) (with current line-skipping, there's no averaging-out of noise, so this just something we may find in the future)
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Fung Wei Liang
New member
Just wondering, will it be useful if I am in a concert (low light) which allows videography and I am far behind. Do you think my 135mm turned into "650mm f2" can record reasonably good footage? I have a 400mm f5.6l but it will record @ ISO 6400 which is usable. If my Maths is correct, my "650mm f2" will record in ISO 400 or 800.
Fung Wei Liang
New member
For those who are interested, I shoot brick wall using the 3x digital zoom and my 17-70 sigma. IMO, the video quality is quite ok. I did not upload the 10sec video as the video is 250MB. But this snapshot is representative of quality as the snapshot is same as video quality.
Sorry, but I don't agree with this. It's only partially true if you ignore lenses specifically designed for smaller or larger coverage, such as 16mm, c-mount, PEN, 4/3, m4/3 etc.
I have 90mm wide angle lenses designed for my 4x5 large format. It's a wide angle design, not a telephoto design like my 85/1.8.
My Sigma 30/1.4 is not a wide angle design, it's a scaled down 50/1.4 design.
True telephoto design means the optic can be shorter than the focal length, eg a 600mm lens does not need to be 600mm long. My 360mm large format lens needs exactly 360mm of bellows to shoot at infinity. This is in fact how the term focal length came to be.
A 135/2 has the DOF of a 135/2. 135/2 is an expression for the focal length and aperture size relative to that focal length, not field of view. Apparent DOF (not physical DOF) needs to take the FOV and sensor/image size into consideration, but the physical DOF does not change.
henryqiu
Well-known member
The depth of field of the 135mm/2 used in this way is not the same as that of a 650mm/9.6 on a FF camera.
Here are some numbers: using 5D2 with the imaginary 650/9.6 lens to take a shot of a subject 50 feet away, you get DoF = about 1 foot. Using a 1.6 crop sensor camera with the 135/2 lens to take a shot of the same subject, you will get DoF = about 1 foot only when the subject is about 25-30 feet away. How do you make sense out of these numbers?
Note: digital zoom alters the field of view (which is a tautology, always true by definition). But it cannot alter the optical attributes of an image that has already been digitized, and DoF is an optical attribute frozen at the moment the image is being digitized.
In fact, if you consider 3x digital zoom as something equivalent to some sort of enlargement, it reduces the circle of confusion and hence becomes a factor that reduces DoF.
Again, digital zoom is merely a digital effect applied to an image already digitized. It does not affect the perspective or the subject-background compression of the image.
henryqiu
Well-known member
What do you disagree with? If you try to use different lenses while trying to maintain the same FoV, you certainly can't get the same images. You disagree with that?
"I have 90mm wide angle lenses designed for..." <-- If the same language is spoken (i.e., in 35mm film terms), this 90mm has to be equivalent to the focal length of, say, a 24-105mm lens zoomed to 90mm. So, 90mm lenses are not wide angle lenses, which is common sense, even though you may get a wide shot with them with a much larger format camera.
"A 135/2 has the DOF of a 135/2." <-- This makes no sense, because DoF is not an attribute of a lens.
The way you are talking about lens designs is... very weird, my friend.;-)
thisisapocalypse
Well-known member
Very good point, I was thinking in FF35 and smaller sensor size terms only, you are correct that there are some differences when you go the other direction into medium and large-format photography, no doubt about that. Perhaps we should be talking about the intended angle of view as designed by the lens given the image size (in terms of degrees) as yes a 90mm on 4x5 or 8x10 has a very wide FOV. That said my point stands that different focal lengths will create images that look different in various respects even when FOV is the same. Here's not a great example, but an example nonetheless comparing a 50mm to an 85mm:
http://www.wlcastleman.com/equip/reviews/50mm/index.htm
And yes you'll see in my earlier post I believe that I referenced apparent DOF (not physical) and if I didn't, I meant to.
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