01-01-2014 02:05 PM
You can take these indoors if you'd like. If the camera is not moving and the subject is not moving, then the shutter speed can be open as long as necessary to get the shot.
For an outdoor shot in full mid-day sun, the sun provides a VERY consistent level of light. There's an easy to remember rule called the "Sunny 16" rule. This says that in full mid-day sun, if you set the f-stop to f/16 then the correct shutter speed will be the inverse of the ISO setting. E.g. at ISO 100 you would use 1/100th. At ISO 400 you would use 1/400th. etc.
Doing a focus test you wouldn't want to use f/16... you want to use f/2.8. BUT... that's an easy conversion.
f/2.8 is 5 full stops down from f/16 (f/16 -> f/11 -> f/8 -> f/5.6 -> f/4 -> f/2.8). That means you just need to compensate for those 5 stops using something else. Assuming you're already at ISO 100 (which is what you should use for a focus test and you should use RAW to ensure the camera does not attempt to apply any in-camera sharpening), you'd count up 5 full stops of shutter speed: 1/100th -> 1/200th -> 1/400th -> 1/800th -> 1/1600th -> 1/3200th.
(BTW... Sunny 16 also estimates how much light is lost for light, medium, or heavy shade or overcast conditions and how to know if your situation calls for "light overcast" vs "medium overcast", etc.)
So: ISO 100, f/2.8 and 1/3200th sec would give you a correct exposure if shooting outside in full mid-day sun (not in the shade.)
Set the camera to take the image as a RAW shot (vs. JPEG) to prevent the camera from applying any in-camera sharpening.
01-01-2014 02:17 PM
just retook using 1/3200, f/2.8, ISO 100... image is darker but still not in focus...this is using the t1i...
01-01-2014 02:25 PM
redid using ISO 100, f/4 and 1/1600th sec and there is no difference... pics look almost identical.... shot in raw and then cropped in PS CS6...
01-01-2014 02:38 PM
results look worse (i think) on the 70d @ ISO 100, 41mm, 1/1600, f/4 ;( i don't know what is going on ;(
i can't open the 70d in RAW in PS CS6 - don't have the new plug in for that camera - so using the jpg for this one/camera...
01-01-2014 02:41 PM
okay so not sure what to do now????? i feel i should return the camera and crawl under a rock .... sigh..... everything is closed today but i believe the camera store that i got the lens from is open tomorrow so going to go to them to see if they have any suggestions .... my fear is that since i didn't get the camera from them they may not be as eager to help ;( but i'm being pesomistic - no need for that right now!
If you have any more suggestions/ideas of things to test/try please let me know!!
01-01-2014 03:46 PM - edited 01-01-2014 03:47 PM
Using the exposure rules that Tim provided and a tripod are you getting a focus confirmation from each camera?
You are focusing right on the printed mark in "one shot"? Not any tracking AF ? Just the center focus point selected in the camera? All camera defaults set to factory?
01-01-2014 05:07 PM - edited 01-01-2014 05:11 PM
when i hand take the shot i see the confirmation (ie it beeps and is red) - to be honest not sure if it is when using remote - ie i don't recall if i heard the beep..... i'm assuming i should even with a remote? right? and yes it is on one shot and the center AF is used.... i didn't change anything on the 70d so should be at factory defaults but will check or at least reset to factory defaults. I've had the T1i for a long time but do not recall changing any settings that may impact the shot but will reset to factory defaults too .... too dark now to redo with natural light so will have to try again tomorrow....
i'm also going to re take the shots using my kit 18-55mm that came with the T1i and my sigma to see what the heck is going on - ie is it only that one lens or all - if all then it's an camera issue - i'd think.... but can someone confirm if that test sheet is a good test for any lens at about 10 feet set to largest aperture? if anything at least it will test if focus is bang on or not right? will try using ISO 100, f/4, 1/1600 if light permits... will recheck Tim's list ot ensure those are the correct corresponding values...
01-01-2014 09:38 PM
You must have focus confirmation one way or another.
The sample shots you posted are, frankly, horrible. It looks like the lens never focused at all, in the first place.
It sounds like you are doing everything correctly. But not actually being there I can not 100% confirm it.
I am having a hard time believing a Canon 24-70mm f2.8 L lens is faulty. It is assembled by the top, best, technicians Canon has. Each one is individually inspected and tested by the best. But as the saying goes, "Anything made by the hand of man can and will fail."
01-02-2014 01:39 PM - edited 01-02-2014 01:41 PM
i just took some more shots....what i'm finding is that at 5 feet or less the lens is sharp... then when i move to 10 feet it starts to not be in focus ..... at 10 feet i'm using a tripod and a remote....
having said that at 5 feet or less that center text is ALMOST there - meaning it's still a tiny bit off... but the numbers down the side are in focus perfectly.... that is at f2.8... i had to use 1/200 and ISO of 200 or 400 ... but that is more becuase of lighting - i just do not have a spot in doors that is bright enough to go to ISO 100 and i can't go outside - it's way too cold ;(
i know all lenses have a workable distance - that they should be used for - how to i confirm what that distance is for this lens?
01-02-2014 03:41 PM - edited 01-02-2014 03:42 PM
"i know all lenses have a workable distance - that they should be used for - how to i confirm what that distance is for this lens?"
Maria you are beginning to lose me here? What do you mean? That lens should be crystal sharp at all distances from min focus to infinity.
Do one last thing for me. Switch off auto focus. Set the camera on the tripod. Manually focus while you are looking through the view finder. Focus on the test spot and do some shots. If it looks to be in focus in the viewfinder it should be in focus period. Use the screen (CRT), not a printer, to view the result.
At this point you don't know anything. Whether the lens is good or the camera is bad or whatever else.
I am banking on the lens being fine.