Lens Quality Question

M

M1CEtro

Active member
I shoot music videos with my 7D. I've done my research on lenses but there is one question that I want more experienced advice on. In perfect/optimal lighting conditions where FStop and ISO are not really a factor, and all other things like shutter, picture style etc. are the same, will a expensive or L series lens give you a "better" or "crisper" picture at a certain focal length (let's say 50mm 1.4 $400) than a cheaper 50mm 1.8 lens $100? I know the build and glass of the 1.4 is better and more sturdy, but with optimal lighting, does that glass really give a crisper picture?

What about an L series zoom versus a regular prime? With optimal lighting and all other factors constant, will an L series zoom set at 50mm give a better picture than a regular prime 50mm $100?

If anyone has illustrative pictures that would help alot too. Thanks
 
You have to remember that 1080 HD video is equivalent to a 2 MP still photo, so it's fairly low rez right from the start, then you have to consider that Canon is line-skipping to down-rez the sensor image to the 1080 HD which introduces a bunch of image problems. ( the worst being low resolution and bad moire with certain image patterns )

To record a "crisper" image you are going to have to look at supplementing your 7D with a different camera. This is why I bought a GH2 to go with my Canon 60D in December 2010, and why I eventually sold my Canon gear ( I could not afford to keep both the GH2 and Canon 60D ) to switch over completely to the GH2 camera. Depending on what the GH3 camera can do ( it's to be released this Fall ), I will either stay with the GH2 / GH3 cameras, or look at switching to the Sony FS-100 / FS-700 camera next year.
 
TheDingo said:
...To record a "crisper" image you are going to have to look at supplementing your 7D with a different camera...
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That is simply not true. There is a very direct correlation between video sharpness and the sharpness of the lens being used on Canon APS-C cams. The problem as you said above comes when the moire and aliasing explode on you at the same settings when using the better L lenses. I never had much issue with those things on vintage lenses or older softer L glass. As soon as I picked up a new 70-200 and 24mm L's I've finally found out why people complain about moire and aliasing so much :)

The main advantages of higher end L glass is in bokeh, color and contrast. Even with the issues of the Canon's, L glass has a look that is quite appealing. Whether that look is worth the cost is another story completely :)

Cheers,
Pete
 
As c3hammer said, there's more to good glass than just "sharp". For example, I wouldn't say the $1500 50mm f/1.2L is sharper than the $120 50mm f/1.8: http://www.the-digital-picture.com/...meraComp=453&SampleComp=0&FLIComp=0&APIComp=0 But the 50mm f/1.8 is not just cheaply built, it just gives you a much uglier image; in particular, bokeh on the 50mm f/1.8 is as bad as it gets. Whereas the 50mm f/1.2L looks absolutely gorgeous. Not that I have one, anyway... I went for vintage glass. I worship my vintange Leitz lenses.
 
c3hammer said:
That is simply not true. There is a very direct correlation between video sharpness and the sharpness of the lens being used on Canon APS-C cams.
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We shall have to disagree here...

1080 HD is video is equivalent to a 2 mega-pixel still photo image, which is fairly low resolution as far as lenses go.

Canon's implementation of video with it's cameras priced under $15,000 is quite soft and low resolution compared to the video image from cameras like the Panasonic GH2 or Sony FS-100. When placed side by side, the image resolution difference is huge, and was the main reason I dumped all my Canon gear back in January 2011. I only wanted a camera for video work and nothing else. ( Canon and Nikon DSLRs are pretty much the standard for still photos, and the Canon $15K+ large sensor video cameras are top notch for video. But the 5D Mk2, 5D Mk3, 7D, 60D, T2i, T3i, T4i all produce a soft and lower resolution video image.

If you want more proof of this, then check out part one of Zacuto's "Revenge of the Great Camera Shootout 2012" which will be released tomorrow. ( June 15, 2012 )

The cameras tested in this new shootout are: Apple iPhone 4s, Arri Alexa, Canon 7D, Canon C300, Panasonic GH2, RED Epic, Sony F65, Sony F3, Sony FS-100
 
TheDingo, we all know the Canon's are soft, but that wasn't the original question. Of course there are much sharper options available. Your suggestion that to get a "crisper" image you have to go to another camera is false though. Great glass on a 7D translates into a significantly "better" and "crisper" image for video and is plainly obvious to anyone. I have numerous samples of a couple vintage wide angle lenses at f/2.0, an older 17-35 L f/2.8, a nifty fifty and the T2i 18-55 kit lens. All of them are mush wide open and completely unappealing to most people relative to my new 24 L. It is simply an amazing thing on a T3i. The Tokina 11-16 f/2.8 is another one that brings a new level of sharpness and appeal to the Canon APS-C video image.

There is no question that great glass is noticably crisper and better, it's whether it is worth the money to contemplate in the first place. For the money a GH2 might fit the bill perfectly, particularly if sharpness is your standard for video.

On a side note, I'm really looking forward to seeing the Zacuto shootout. I will predict that in order for the GH2 to have been picked so highly, the scene will have to have been relatively dark with relatively low DR.

Cheers,
Pete
 
c3hammer said:
Great glass on a 7D translates into a significantly "better" and "crisper" image for video and is plainly obvious to anyone.
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It depends on whether you are measuring contrast or resolution.

Resolution is a problem because even average Canon glass is going to out resolve what a good 1080 HD sensor can record, so switch to outstanding glass and the image has pretty much the same resolution because the 1080 HD sensor can't really record the difference.

Contrast is very noticeable, where even a horrible sensor will still show contrast improvements with great glass over "flat" low contrast glass.

c3hammer said:
All of them are mush wide open and completely unappealing to most people relative to my new 24 L
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If you take an average lens ( say non-L glass Canon equivalent ) and stop it down 1 to 2 stops, the image it produces will be very close to what the L-glass is producing at the same F-stop. The cheap kit lenses are junk, but if you compare non-L EF prime lenses the results are not much different. One of my favorite non-L lenses was the Canon EF 100mm f/2.0, which had overall performance that was similar to L-glass, even wide open.

c3hammer said:
On a side note, I'm really looking forward to seeing the Zacuto shootout. I will predict that in order for the GH2 to have been picked so highly, the scene will have to have been relatively dark with relatively low DR.
Click to expand...

I think the GH2 did as well as it did because the camera has a very good 1080 HD sensor, and the camera crew did a great job in adjusting the room lighting to lower the overall contrast to meet the limited dynamic range that the GH2 can record. ( the GH2 is a contrasty camera, but if you know how to deal with it's limited DR you can get outstanding results )

In the end I think that the new Zacuto shootout will prove that you can produce top-quality results with fairly cheap cameras if you really know what you are doing.
 
I think you're both kind of right, but I'd line with c3hammer: the summary is that lens sharpness matters for DSLR video, a lot. Yes, it's only 2 mpix, and yes, it's not "resulution" that you're looking for, but what you call "contrast" (which I'd call "acutance"), but both are very closerly correlated. And yes, stopping down makes most lenses look sharp, but I don't shoot f/8 very often, I'm usually at f/2.8 to f/4. Take for example the much-praised Tamron 17-50 f/2.8 non-VC. I know it's a great lens, it's my usual suggestion for people looking for a standard APS-C zoom. But my copy is soft in the long end: at 50mm, it has to be stopped down to f/5.6 to be sharp in the center. My tests (with simulated line skipping and column skipping, i.e. stills downsampled to 1920x1080 using nearest neighbor) are here: http://www.similaar.com/foto/lenstests/lenstestsw.html And don't mock the kit lens: it's surprisingly sharp, just slow and crappily built, but not soft, by any standards.
 
the 'weight' of the focus ring on more expensive 'metal' lenses tends to give a more appealing picture. not once have i seen a lovely fluid focus pull on a cheap canon 50mm f1.8.

a better lens will be sharper at wider apertures meaning you can be more creative with shallow depth of focus while keeping your subject sharp. close the apertures down to f5.6 or higher, with adequate light and it'll be hard to tell a difference in sharpness in 1080p.
 
I find feeding the sensor a slightly softer picture helps with overall aesthetic 'quality'. the less sharp edges, the less the camera can ruin with codecs and other artifacts!
 
I try to stay at 5.6 (just as I would for a still) unless desire for shallower DOF, or lighting I can't control drive me lower than that.
That area, 4 to 8, is the sweet spot on most lenses. That's usually one of the things you use to evaluate a lens, how "crisp" does it look at lower F stop numbers. My primary lens (probably 60% of my shots) is the Takumar 50mm 1.4 which was always a respected lens because it's tack sharp at 2.8.
 
TheDingo said:
It depends on whether you are measuring contrast or resolution...
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I'll concure that what I'm calling sharpness is partly due to more contrast (acutance) with better lenses. I have also found that with faster glass you can generally use a lower ISO setting which also lends to a sharper image. I've found that for poorly lit documetary work, the combination of resolving power, acutance and speed of a lens allow for what I would call a radically "crispier" image. While a GH2 might be a great camera for controlled lighting it's horrible for blown highlights and the high contrast associated with mid day sun. The Canon's do a much better job with the type of work I do. Adding great glass to a Canon APS-C cam doubles down the range it will perform well in. Not in pure resolution, but in where you can tell your story in nearly the highest quality available.

Cheers,
Pete
 
Basic lens fundamentals. If you want sharpness, you shouldn't be shooting f1.anything. Aperture of f4-8 is the sweet spot of most lenses, if I'm not mistaken. David Mullen shoots most scenes between f4 and 5.6, I believe. Unless you're obsessed iwth blurry backgrounds, or it's completely dark...

PS -- He beat me to it, above.

Test your lenses at various apertures.
 
Hello All, thanks for your comments on this.

Reading through all of these posts has brought up a concept I never considered before. Shooting with my 7D for video, (with the exception of daytime shooting) I'm so used to using the lowest F stop possible on every lens so I can keep the ISO as low as possible and have minimum noise. But from what I'm reading, it seems like some of you are saying that a lens may produce a "sharper" image at an F-Stop other than the lowest stop? That there is a sweet spot for sharpness on a lens? I was under the assumption, that with non optimal lighting, the lowest F Stop (most of the time at 1.8) will produce the best image, is this not the case? My workhorse is a 28mm 1.8 prime. How would you suggest that I test to find the sweet spot of my lens for video?
 
M1CEtro, do not confuse best with sharpest. For portraits, or even IV's, you don't always need maximum sharpness, so using lower F-stops makes sense. If you're trying to show a close up a jewelery, you'd want it as sharp as possible to show the detail, so you'd want to use the lens around f/4 or 5.6 to get maximum sharpness.

It's all a matter of balancing your needs in each situation, and it may well be that in sub-par lighting you will still get the best overall image by shooting wide open, as per your assumption. Sharpness is no good if it's too dark to see the image!

As for finding the sweet spot of your lens, the easiest way is probably to scan through some reviews of your lens. Most professional reviews will test the lens at each F-stop and note the sharpest aperture.
 
If you really want a "sharp" image, don't forget to apply some fairly aggressive sharpening to counteract the strong anti aliasing filter in the Canon.

When Canon released the 1DsII (pre video days), Chuck Westphal recommended in a white paper that you use an unsharp mask in Photoshop at (300, .1, 1) as a standard "capture sharpening" step (as opposed to later sharpening for creative or output purposes.)

Those of you who are familiar with Photoshop will realize that is a pretty aggressive sharpening setting - higher than I would have tried without having someone recommend it. The current 18 MP crop sensors have a smaller pitch, but they are fairly similar to that 16MP sensor in the 1DsII. There is a lot of information in the image that can be brought back. (I sharpened a still image last night at (300, .9, 1) for text legibility.)

Now it all really depends on the final destination for the image, content, aesthetic, etc. I used to mask the face on portraits, or apply blur to the face to lose sharpness and detail for fashion images. But the strong AA filter in the Canon **can** be counteracted by appropriate software techniques.

Actually if you look at the Nikon D800E, people say it has "no AA filter." That is actually not true - it has two filters, one AA filter, and a second filter that immediately "undoes" the AA effect - reverses the effect. (Most people assume that was to keep the same image path intact from the D800 to the D800E.)

That is the same concept of capture sharpening in software with PS. It really is quite effective in regaining detail where you want it back.

Pretty similar in concept to using flat, low saturation, Adobe RGB images out of the camera to render a final look. Beginners always used to complain that Canon images were flat, didn't have that "pop" - which is really a good thing. They weren't high saturation, sharperned, sRGB images for teh web. Don't take that initial image as a given.

On lenses - "L"'s for most zooms are almost as good as non-L primes (in general). L primes are usually better than non-L, with some exceptions (on the non-L's being pretty decent, not the L's really being poor.)

Canon is updating most of their line - 24, 28, 24-70, etc. But the new lenses are not cheap. The one I lust after is the 24-70 II. I use my 24-70 I about 70% of the time (then the 70-200 next, then 24, 50, 85.) If I had only one lens the 24-70 L II would be it. But at $2,300 you can buy a whole raft of non-L primes. (Canon lenses retain their value pretty well though, so I don't mind spending more for some. The true cost is purchase price - sale price.)

Good luck!
Michael
 
Lenses are typically sharpest in the middle of their f-stop range, so usually at least 1 stop down from wide-open, and at least 1 stop up from fully-closed; for many lenses, it's better to go 2 stops down or 2 stops up.

So on an f/1.8 lens (let's call it f/2) the sharpest range is usually going to start at about f/4. Lenses used wide-open will usually be softer, have more vignetting, and be prone to more flare.

The problem with getting the sharpenst lens on a 7D is that the sharper the lens, the more you'll see aliasing. A softer lens can actually deliver all the resolution that the 7D can handle, and sometimes softens the image enough that it helps minimize the aliasing.
 
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