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Thinking of buying an AC160, but worried about coma/aberration

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Stephen CryeThinking of buying an AC160, but worried about coma/aberration
by on Apr 15, 2012 at 2:21:45 am

Hi;

I'm hoping that owners of the AC160 or AC130 can help me out by shooting some tests and posting the links.

Some of you may know of my struggles since Oct. 2011 to find my first "pro" cam. I've bought, tested, and rejected: three separate Sony NX70s, a Sony NX5 and a Sony VG20. The Panny AC160 is now on my radar. it has a lot of features I will love, some that will annoy me, but I really want to make sure it does not suffer from my biggest show-stopper fail - excessive coma/CA.

One positive thing that is making me lean toward buying the Panny is the fact that Jan Crittenden seems to be an active participant in these forums. (Jan, we are hoping for good word about the AVCHD 2.0 upgrade for the AC160 tomorrow!) Jan, any insight you can give about the coma/CA I describe below would be greatly appreciated.

I've been looking at various videos from the AC160 on the 'net, and I've noticed a disturbing pattern: red coma above overexposed objects. They are particularly noticeable on car headlights or streetlights at night. Please watch the following samples at 1080 and look closely for the coma/CA:

Here are three vids that show what I mean:




( 1:59 for an example)




(besides the lights, check our the bokeh at 3:49 - CA is always red on top)

But, not all the vids I have found show the problem. In particular, this one looks perfect at 1:04 during the undercrank test. (makes me wonder if there is something special happening during undercranking?)






I would greatly appreciate everyone's input on this. I really, really don't want to have to return another cam to B&H. Aside from the hassle and shipping costs, I fear that they are close to cutting me off!

Thanks,

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e (and 11) x64 DVDA 5.2(build 133) Sony HDR-CX550V


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Guy McLoughlinRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 15, 2012 at 1:37:59 pm

Hi Steve,

I don't think the examples you point to are caused by chromatic aberration.

What you are seeing is light "bloom" which every camera ( including film cameras ) exhibit when shooting high contrast over exposed light sources.

The "red" color comes from filming sodium-vapor street lights, which are partial spectrum sources, and will always look "red". ( sort of an orangey-red )

Notice that other over exposed light sources ( non sodium vapor lights ) like car headlights, red streetlights, etc... also show "bloom" but not the "red" color of the sodium vapor lights.

My own personal concern with the new Panasonic AC130 / AC160 / HPX250 cameras was lens flare, but after trying the camera out, I found that lens flare is very well controlled. ( much better than the Canon cameras I was using to compare )

Optically, I don't think you are going to find any real issues with the lens on these new Panasonic cameras. Overall it's a very good lens.

- Guy


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Stephen CryeRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 15, 2012 at 4:35:34 pm

Thanks, Guy.

I hope you don't mind some follow-up. Trust me, I want to believe you! I'm itching to place the order.

Let's accept your sodium-vapor hypothesis. Can you explain why the reddish bloom is only on the top of the overexposed lights? Also, I see the same pattern of "red on top" even with overexposed items that are not lights, and the same "red on top" in out-of-focus images, such as in this video at about the 10 second mark. (Also notice the yellow on the bottom of the bokeh).






And, in this vid, I see the red-on-top in the out-of-focus overexposed shots of the full moon - reflected sunlight from the moon is pretty much the definition of pure white light:






I've also seen the same re-on-top problem in shots of leaf gap bokeh with sky behind the leaves, but I can't find that video right now.

But, on other videos, the bokeh looks perfectly color-symmetric, as in this vid at ~ 35 seconds:







And in this post, "iSi" includes a screen shot of the same reddish CA on top of the little ornamental architectural object. Now, please understand that this example shows a very minor amount of fringe; what worries me is that it is the same color as what I am seeing in the night lights shots:
http://www.isi-asia.net/download/A-resort-in-Pattaya-ca.jpg

I have read (and want to believe) that the AC160 has Chromatic Aberration Compensation (CAC) built in. Adam Wilt of ProvideoCoalition claims that it only works on lateral CA.

While I have your attention, any other observations you have about the AC160 would be great - things you like, things that bug you. I've heard complaints about the auto-focus, the lack of expanded focus and being forced to rely on Peaking, and the lack of magnification in the EVF eyepiece.

Thanks!

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e (and 11) x64 DVDA 5.2(build 133) Sony HDR-CX550V


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Guy McLoughlinRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 15, 2012 at 8:54:20 pm

[Stephen Crye] "And in this post, "iSi" includes a screen shot of the same reddish CA on top of the little ornamental architectural object. Now, please understand that this example shows a very minor amount of fringe; what worries me is that it is the same color as what I am seeing in the night lights shots:
http://www.isi-asia.net/download/A-resort-in-Pattaya-ca.jpg

I have read (and want to believe) that the AC160 has Chromatic Aberration Compensation (CAC) built in. Adam Wilt of ProvideoCoalition claims that it only works on lateral CA."


...Looking at this example, I can clearly see what you are talking about. Yes, this looks like CA to me, but it seems like it's only a problem with over-exposed whites against a darker background. If you plan on doing a lot of night shooting, then I think you may have to by-pass on these Panasonic cameras, but I honestly can't say which camera brand will perform better under the same conditions. ( i.e. Wide-open Low-light shooting with lots of subject contrast )

I've seen the same problems with both Canon and Sony prosumer cameras, and often the longer/faster the lens the worse the CA performance is when shooting wide open.

Even DSLR still photo prime lenses will show objectionable CA when shooting at maximum apertures, but the CA becomes properly controlled once the lens is stopped down a bit.

I would be curious to see if the Panasonic CA problem goes away once the lens is stopped down 1 or 2 stops. ( makes for a very slow lens under low-light conditions, but are there any other options ? )


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Martin VeronaRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 17, 2012 at 2:19:39 pm

HI Guy,

I have been researching the Panny AC 160 as well. Coming from a Sony PD150/VX2000 combo I am cautious about Panasonic. I shoot alot of stage productions. How accurate is the auto focus? Especially when the stage lights may be dim? My attraction to the AC 160 is the ability to record to backup SDHC cards. Any insight into this camera would be appreciated.

Martin
http://www.videocamtvproductions.com

"Memories of today, Recorded for tomorrow."


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Stephen CryeRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 17, 2012 at 5:00:42 pm

I ordered an AC160 yesterday from B&H - they had a good price.

I too do a lot of stage videography. I have feeling I will need the $300.00 focus upgrade. Also worried about noise in low light; I'm spoiled by my little Sony CX550V which is very clean all the way up to 18dB of gain. Will let everyone know my test results. Cam won't be here until next week.

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e (and 11) x64 DVDA 5.2(build 133) Sony HDR-CX550V


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Guy McLoughlinRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 17, 2012 at 10:10:49 pm

Hi Martin,

Panasonic have announced upgraded "A" versions of the AC130 / AC160 cameras, this upgrade can also be purchased by current owners of these cameras for $300.

Panasonic Introduces Upgrades to AG-AC160A and AG-AC130A, Newest Generation of AVCCAM HD Handheld Camcorders

The main features of this upgrade are "expanded focus assist" and "turbo speed one-push auto focus function". If you plan on shooting stage productions, I would definitely wait to buy the upgraded camera.

That said, I have shot a few theatre productions with my Panasonic HMC-150 camera using manual focus, and had little trouble keeping focus as I zoomed and panned across the stage. ( anticipating the actors movements has always been trickier for me, unless I've seen the performance a couple of times )

These newer Panasonic AC130/AC160 cameras, are much sharper than my HMC-150, which is more of a 720 HD camera than a true 1080 HD.

If you don't want to go Panasonic then the other option to consider is a new or used Sony EX-1R which is very sharp, great in low-light, with a good autofocus system. The main drawbacks with the EX-1R are a shorter zoom range, a more expensive camera, and a less ergonomic camera. ( harder to hand hold )

You might even consider renting each of these cameras if you are undecided on which to buy.


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Stephen CryeRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 18, 2012 at 5:03:01 pm

HI;

While the Sony EX1 is unquestionably a solid cam with a lot of great features, for me it would not work. I need at least 1080 60p, don't care about "broadcast quality MPEG codecs", and just can't afford SxS cards!

Keeping my fingers crossed that the AC160 will be the Cam For Me. ETA 4/23/12.

FYI:
http://pro-av.panasonic.net/en/sales_o/broch_pdf/ag-ac160a.pdf

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e (and 11) x64 DVDA 5.2(build 133) Sony HDR-CX550V


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Guy McLoughlinRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 20, 2012 at 1:42:33 am

Just wanted to pass this along...

DvxUser: Loving my 130 for theatrical use!


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Stephen CryeRe: Thinking of buying an AC160, but worried about coma/aberration
by on Apr 20, 2012 at 1:48:08 am

Thanks for the link, Guy!

Three days to go ...

I wish Jan Crittenden-Livingston would respond to my other post about the details of the AC160 $300.00 focus upgrade. Hopefully she is just busy with post-NAB stuff.

Steve

Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e (and 11) x64 DVDA 5.2(build 133) Sony HDR-CX550V


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