A couple of queries about the 7d (Aliasing/Data rates) ? at DVinfo.net

Mat Thompson · November 9th, 2009, 04:31 AM

Hi guys
I'm thinking of buying a 7d as my 20d needs updating and the video functions would certainly help for certain things as well that my current JVC GY HD110 can't do. (Low light/ 720/60)

I'm particularly interested in the 720p60. However after reading a review they highlighted an aliasing issue in this mode that does look an issue to me. If you look at the sample on the link below (sample4) you certainly can see the aliasing along diagonal edges !? - Any thoughts on this?

Also they list the data rate as 5.5mbps !? - This seems very low?

Canon EOS 7D Review: 19. Movie Mode: Digital Photography Review

Cheers
Mat

Andy Wilkinson · November 9th, 2009, 06:05 AM

Hi Mat. I think you're confusing Mega Bytes (MB) with Mega Bits (Mb)...but I may be wrong...it's a common mistake I think but for sure the 7D encodes at around 45 Mega Bits per second for it's HD video formats. That's good and robust!

Can't comment extensively on the aliasing etc. thing as I've only had my 7D for a few days - and I plan on using 1080p most of the time with it anyway (this issue is said to be worse at 720p). Certainly, I'm not expecting it to be as crisp/fault free as my EX3 - but this 7D cost a fraction of the cost of that and is primarily a DSLR ....so you have to be fair on these things! I think it really depends on what kind of stuff you plan on shooting. Lots of wide shots of, typically, "man made items" will look worse in 720p because of this limitation (unless you do what most skilled people seem to do with these cams and deliberately throw all that stuff out of focus whilst filming say a talking head). And, for example, if 90% of your output is for web (I don't know what you plan), few except us techie camera freaks will ever notice these issues anyway. Whatever, for me, this issue (I prefer to call it a weakness) is worth bearing because of all the things the 7D CAN DO.... and can do REALLY WELL at it's price point (not to mention it's also a lot more portable than my other cam!). Every cam has it's limitations and strengths - well the ones in my price range anyway!

Difficult decision but hope that helps a bit. I was agonising over all this stuff 2 weeks ago so I know how it is.

Ian G. Thompson · November 9th, 2009, 11:11 AM

Well said Andy. It is 5.5 Megabytes per second which I believe comes out to 48 Megabits per second. That is a very robust codec indeed. Also the issue with aliasing/moiré is like you said…primarily in 720/60p but really…I’ve seen tons of footage that avoided it or minimized it. The 1080p in this cam is excellent despite the fact that test charts show it (and the 5Dll as well as all DSLRs) does not resolve as much detail as conventional camcorders. Real world footage is what counts.

Mat Thompson · November 9th, 2009, 01:06 PM

Ah ha....megabytes /megabits - Ok yeah that would solve that confusion !!

Oh don't get me wrong I've see some excellent things done with this tool and it will certainly fill gaps that my camcorder struggles with. But the 60p was certainly something of interest and although in nature (which is what primarily it be used for) straight lines aren't very common I thought it was worth asking the question. I have seen quite a bit of 60p that looks very nice from the 7d but this issue was raised on a well respected site albeit with a bias towards still shooting.

Thanks for giving me your thoughts!

November 9th, 2009, 04:31 AM	#1
Mat Thompson Trustee Join Date: Sep 2006 Location: Kent UK Posts: 1,397	A couple of queries about the 7d (Aliasing/Data rates) ? Hi guys I'm thinking of buying a 7d as my 20d needs updating and the video functions would certainly help for certain things as well that my current JVC GY HD110 can't do. (Low light/ 720/60) I'm particularly interested in the 720p60. However after reading a review they highlighted an aliasing issue in this mode that does look an issue to me. If you look at the sample on the link below (sample4) you certainly can see the aliasing along diagonal edges !? - Any thoughts on this? Also they list the data rate as 5.5mbps !? - This seems very low? Canon EOS 7D Review: 19. Movie Mode: Digital Photography Review Cheers Mat

November 9th, 2009, 06:05 AM	#2
Andy Wilkinson Inner Circle Join Date: Sep 2007 Location: Cambridge UK Posts: 2,853	Hi Mat. I think you're confusing Mega Bytes (MB) with Mega Bits (Mb)...but I may be wrong...it's a common mistake I think but for sure the 7D encodes at around 45 Mega Bits per second for it's HD video formats. That's good and robust! Can't comment extensively on the aliasing etc. thing as I've only had my 7D for a few days - and I plan on using 1080p most of the time with it anyway (this issue is said to be worse at 720p). Certainly, I'm not expecting it to be as crisp/fault free as my EX3 - but this 7D cost a fraction of the cost of that and is primarily a DSLR ....so you have to be fair on these things! I think it really depends on what kind of stuff you plan on shooting. Lots of wide shots of, typically, "man made items" will look worse in 720p because of this limitation (unless you do what most skilled people seem to do with these cams and deliberately throw all that stuff out of focus whilst filming say a talking head). And, for example, if 90% of your output is for web (I don't know what you plan), few except us techie camera freaks will ever notice these issues anyway. Whatever, for me, this issue (I prefer to call it a weakness) is worth bearing because of all the things the 7D CAN DO.... and can do REALLY WELL at it's price point (not to mention it's also a lot more portable than my other cam!). Every cam has it's limitations and strengths - well the ones in my price range anyway! Difficult decision but hope that helps a bit. I was agonising over all this stuff 2 weeks ago so I know how it is. __________________ Andy K Wilkinson - https://www.shootingimage.co.uk Cambridge (UK) Corporate Video Production

November 9th, 2009, 11:11 AM	#3
Ian G. Thompson Major Player Join Date: Jan 2007 Location: Rockledge, Florida Posts: 351	Well said Andy. It is 5.5 Megabytes per second which I believe comes out to 48 Megabits per second. That is a very robust codec indeed. Also the issue with aliasing/moiré is like you said…primarily in 720/60p but really…I’ve seen tons of footage that avoided it or minimized it. The 1080p in this cam is excellent despite the fact that test charts show it (and the 5Dll as well as all DSLRs) does not resolve as much detail as conventional camcorders. Real world footage is what counts.

November 9th, 2009, 01:06 PM	#4
Mat Thompson Trustee Join Date: Sep 2006 Location: Kent UK Posts: 1,397	Ah ha....megabytes /megabits - Ok yeah that would solve that confusion !! Oh don't get me wrong I've see some excellent things done with this tool and it will certainly fill gaps that my camcorder struggles with. But the 60p was certainly something of interest and although in nature (which is what primarily it be used for) straight lines aren't very common I thought it was worth asking the question. I have seen quite a bit of 60p that looks very nice from the 7d but this issue was raised on a well respected site albeit with a bias towards still shooting. Thanks for giving me your thoughts!