I have one 6D myself, now I got 2 lens: 24-105mm f4L for multiple purposes, and 85mm f1.8 for take portrait photo. Now I am looking for a tele lens. I am confuse between 70-200mm f4L is usm and 70-300mm f4-5.6L is usm. Can someone give me an advise? Thank you guys!
70-300 can zoom in more but don have Constance aperture so when u zoom video will become darker
70-200 has Constance aperture of f4 so when you zoom the brightness stay the same
Thanks, I got it. But I want to ask about the quality of photo. I also little bit prefer f4 than f4-5.6, however the other got zoom in 300mm. I think I am ok with 200mm
I am using the 70-300 L zoom. The pictures are sharp. The IS helps when I shoot without tripod. I prefer this lens to the 70-200 F/4 because of the little extra zoom. However note that the F/4 is lighter by about 300g. Both the lenses are not as good as the F/2.8 when it comes to shooting in low light situation. I have to compromise by upping the ISO.
I am using the 70-300 L zoom. The pictures are sharp. The IS helps when I shoot without tripod. I prefer this lens to the 70-200 F/4 because of the little extra zoom. However note that the F/4 is lighter by about 300g. Both the lenses are not as good as the F/2.8 when it comes to shooting in low light situation. I have to compromise by upping the ISO.
If you can see the specks in your viewfinder but not in the picture or mirror, then it is highly probable that the dust is on the focusing screen.Anyone send your 6d for sensor cleaning before?
After shooting aggressively for a few mths i spoted 2 dust in my view finder.. i cant see it in the mirror so it might be in the sensor. it also don appear in the picture. so i cant really tell where is the 2 dust
i wanna send to canon for sensor cleaning but i don know what does low-pass filter means
If you can see the specks in your viewfinder but not in the picture or mirror, then it is highly probable that the dust is on the focusing screen.
You can also test and see if the dust specks are visible on the LCD when using live view. If you cannot see it, then your sensor is clean.
I had the same experience a couple of months ago. Try using a blower first. Do not lock up the mirror or the dust will get on your sensor.
It is a difficult choice between these two lenses because each have their strengths and weaknesses. It will depend on your need. Here's an excerpt from The-Digital-Picture website:Actually I am looking for an EF 70-200mm F4L IS USM, but is 70-300mm sharper?
The Canon EF 70-200mm f/4.0 L IS USM Lens is one of the most impressive zoom lenses available. It is sharper than the 70-300 L wide open and has a max aperture advantage in the long end of the shared focal length range. With a 1.4x extender attached, the 70-200 f/4 IS goes to 280mm, but the 70-300 L has an image quality advantage at this length. The 70-200 f/4 IS is a smaller lens and it does not extend.
Based on what you say, the dust is somewhere along the lightpath to your viewfinder : Lens (a) -> Mirror (b) -> Focusing Screen (c) -> Prism (d) -> Viewfinder (e). - and any elements in between. If you have been changing focusing screens, then it might be possible that the dust got into the area between the focusing screen and the viewfinder. If it really bothers you (it bothered me when I had those specks in my viewfinder) , then maybe a visit to the service centre may be advisable.i change to another focus screen , i saw the same thing
its not in the live view or in picture..i shoot in white light to see also...
6D now listed as discontinued. Wondering what kind of successor canon will come out.
Although my usage of it is quite low 
It is a difficult choice between these two lenses because each have their strengths and weaknesses. It will depend on your need
What this means is that the F/4 will be sharper wide-open for the zoom range 70mm - 200mm. If you are shooting at a high zoom and using an extender for the 70-200, then the 70-300mm is sharper. This is for situation when shooting wide open. I think the difference in sharpness is insignificant if you stop down. I normally shoot at >200mm when using this lens and also between F/5.6 and F/8. That was the reason why I picked this lens over the 780-200 F/4.
You need the select the one that best suit your photography style/needs.
I know it's too early now but any good guess when mark ii will be out in market? Already noticed few 6d out in classified ad probably waiting to jump onto mark ii
But others online retailer still selling as per norm...But amazon uk already put model is discontinued from manufacturer