DOF at f2.8

EMA747

EMA747

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Andy
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I am still getting used to my Canon 70-200 f2.8 and it's DOF.

I was just taking a pic of some reels of thread lined up on a table so that I could test the DOF. The camera was about 1.5m away from the threads and I used f2.8 and focused on the middle reel in the row. I just got a blur and no part was in focus. I had to go up to at least f6.3 to get anything in focus. Is this what's to be expected at these distances from the lens and apertures?

PS the lack of areas in focus was not to do with camera shake as all were taken on a tripod with shutter release and IS on.
 
I recon you have the min focus distance switch set to 2.5m+, try setting it to -1.4.
 
if you were at 200mm the total dof is 5.2mm - have a play here
Subject distance 150 cm


Depth of field
Near limit 149.7 cm
Far limit 150.3 cm
Total 0.52 cm

In front of subject 0.26 cm (50%)
Behind subject 0.26 cm (50%)

Hyperfocal distance 74452.3 cm
Circle of confusion 0.019 mm
 
admirable - I did have 1.4 selected.

bbb - I thought the IS on the f2.8 versoin was tripod detecting.


Here are some shots of what I did. They are totally unedited apart from converting to jpeg and cropping, no sharpening added.


f6.3, 1.3 sec, 200mm, ISO 100
f28-800.jpg


100% crop of above image. - Focus point was set for the middle if the green reel.
f28-100.jpg



f2.8, 1/4 sec, 200mm, ISO 100.
realf28-800.jpg


100% crop of above image. - Focus point was set for the middle if the green reel.
realf28-100.jpg



Neither appear to be as sharp as I would expect. The f2.8 is not sharp at all anywhere on the image.
The f6.3 seems to be sharper on the wood at the top of the reel rather than the thread part which the focus point was set for.
 
May be try it with IS off, since it's mounted on a tripod. Also, try them with mirror locked up?
 
EMA747 said:
I am still getting used to my Canon 70-200 f2.8 and it's DOF.

I was just taking a pic of some reels of thread lined up on a table so that I could test the DOF. The camera was about 1.5m away from the threads and I used f2.8 and focused on the middle reel in the row. I just got a blur and no part was in focus. I had to go up to at least f6.3 to get anything in focus. Is this what's to be expected at these distances from the lens and apertures?

PS the lack of areas in focus was not to do with camera shake as all were taken on a tripod with shutter release and IS on.
Click to expand...

Did you have MLU on? Also, if those shots at f2.8 are unsharpened RAW just converted to JPG I reckon that's about as good as it gets.
 
I'd up the iso, or bring in some more light, shoot a decent shutter time.
If they are sharp, then you have movement..if not something else is a miss
 
Gofer said:
Did you have MLU on? Also, if those shots at f2.8 are unsharpened RAW just converted to JPG I reckon that's about as good as it gets.
Click to expand...

What is MLU?
 
Gofer said:
Did you have MLU on? Also, if those shots at f2.8 are unsharpened RAW just converted to JPG I reckon that's about as good as it gets.
Click to expand...

PerfectSpeed said:
Yep, gonna have to run some USM there.
Click to expand...


Givvover you two...:lol:

I dunno anything about canon cameras or lenses but if mine was shooting that they'd go straight in the bin.
Now unless somebody's got a "its soft at 2.8 but sharpens at 6.3" get out clause for this particular lens, how are we gonna explain the difference in sharpness between the two.
I'm not saying its even sharp at 6.3, but its sharper than 2.8 and a longer shutter time.
We're at 200mm, with shutter times measured in seconds, on an unknown tripod, maybe on floorboards in a house....:suspect:
 
Look, this lens is simply awesome. But 1/4 second exposure at 200mm is rediculous.

The DoF gets longer as you get further away from the subject. Look at this.
 
He's standing on your tripod!
 
Can you try it at a faster shutter speed? Turn on the lights, up the ISO, use a flash... whatever you like but let's get the shutter speed to 1/100 or even 1/200 and see the results.
 
I'll try it again with IS off and up the ISO.
 
Ok I tried some more with ISO 1600 and IS off. I also tried them against my old Tamron to see how they compare. See what you think.


f2.8, 1/125 sec, 165mm, ISO 1600, 100% crop - I had IS on for just this shot to see how it compares to the one below this.
f28tripod.jpg


f2.8, 1/125 sec, 165mm, ISO 1600, 100% crop - IS off.
f28notripod.jpg


f5.0, 1/50 sec, 165mm, ISO 1600 Canon lens
f50Canon.jpg


f5.0, 1/50 sec, 165mm, ISO 1600 Tamron lens
f50Tamron.jpg


f7.1, 1/25 sec, 165mm, ISO 1600 Canon lens
f71Canon.jpg


f7.1, 1/25 sec, 165mm, ISO 1600 Tamron lens
f71Tamron.jpg



The Tamron shots don't look to me that much sharper. At least not as much as I would have expected.
 
How are you releasing the shutter?

Is the lens mounted via a tripod collar?
 
CT said:
How are you releasing the shutter?

Is the lens mounted via a tripod collar?
Click to expand...

I am using a shutter release cable. It is mounted to the tripod by the collar that comes with the lens. Also the tripod is a big old sturdy one so no shake from that.
 
1/25th is still very slow for 165mm
 
OK Ema. This is one of your original resized shots just sharpened and wb and levels adjusted.

3975035459_2accaeb6f5_o.jpg


I'm not seeing much wrong tbh. Any shot which has been reduced in size will lose definition and absolutely MUST be sharpened at the reduced size.

Also, you shouldn't necessarily expect a digital file straight from your camera to be at it's sharpest, in fact it's often advocated to disable all sharpening in the camera and deal with it in post processing for the sharpest images.

The Canon lens certainly seems to be easily out-performing the Tamron.

Are you shooting jpegs or RAW?

Hope that helps?
 
CT That does help. I am shooting RAW in reply to your question. I am aware of needing to sharpen in PP but I just thought it seem like I had to sharpen a LOT.
Also can you tell me what sharpening you did to the above pic?

One thing that make me slightly wonder if the lens is out is that there was a small dent on the box when it arrived in the post. There is no visible damage to the lens but you don't know what happens in the back of a post van! :naughty:
The other thing is that I have had a Canon 17-40 L for about a year and straight away when I first got that I was saying WOW this is soooo sharp. I am just not getting this with the 70-200 at the moment. (see point below though)

To be honest I haven't really had chance to test it outside in good light so until I do that I can't really tell if it's ok in real world situations. Taking pics of threads in such low light is not really what this lens is about at the end of the day. ;)
I shoot a lot of aviation and had a Canon 100-400 that I had to sell. I still have a few RAW files from it on my hard drive so when I can get down to the airport and shoot some planes in good light I will soon be able to compare the results. I know the 100-400 was a very sharp copy.
 
Here's a sharpened version of your 100% crop Ema. Look at the fine detail of those whispy strands on the left edge of the reel which is where you seem to have focused. It doesn't really get much better than that when viewing the full sized file, in fact looking at your original 1:1 crop I would consider it a good file which would sharpen up well if it was one of mine.

3975833706_03bb0be06c_o.jpg


You're right though - it's not really a lens meant for shooting cotton reels, I'm sure when you get out and take some aviation shots it will blow your socks off. :D

I have this lens and it's an absolute cracker.

Sorry I forgot to say I just gave the image a couple of shots of the sharpen filter in Paint Shop Pro. You're probably better using USM sharpening in small amounts and watch out for halos or sudden unnatural looking highlights appearing in which case you've overdone it. Sharpening just needs a bit of judgement -that's all.
 
CT If I can work out how to send it to you would you be able to have a quick look over the original RAW file that the above 100% crop?
 
I can PM you my e-mail addy if you like. If your ISP will allow you to send a large file I can receive it - but in all honesty, it wont tell me anything I can't see looking at the crop, and I'll confidently say there's nothing wrong with your lens. :)
 
Ema don't think about it to much

i have this lens and i use it like a bazooka

aim and fire
it's so fast at focusing as long as you have the focusing distance set correctly
and the results rarely disappoint
as for the dented box, i'd be surprised if a minor box dent had affected anything because it's a bullet proof bazooka :D
 
EMA747 said:
Ok I tried some more with ISO 1600 and IS off. I also tried them against my old Tamron to see how they compare. See what you think.


f2.8, 1/125 sec, 165mm, ISO 1600, 100% crop - I had IS on for just this shot to see how it compares to the one below this.
f28tripod.jpg


f2.8, 1/125 sec, 165mm, ISO 1600, 100% crop - IS off.
f28notripod.jpg


f5.0, 1/50 sec, 165mm, ISO 1600 Canon lens
f50Canon.jpg


f5.0, 1/50 sec, 165mm, ISO 1600 Tamron lens
f50Tamron.jpg


f7.1, 1/25 sec, 165mm, ISO 1600 Canon lens
f71Canon.jpg


f7.1, 1/25 sec, 165mm, ISO 1600 Tamron lens
f71Tamron.jpg



The Tamron shots don't look to me that much sharper. At least not as much as I would have expected.
Click to expand...
To me the Canon are better then the Tamron BUT you say you shoot in RAW and are not added any sharpening You have to sharpen all your RAW files its a fact.
 
CT said:
I can PM you my e-mail addy if you like. If your ISP will allow you to send a large file I can receive it - but in all honesty, it wont tell me anything I can't see looking at the crop, and I'll confidently say there's nothing wrong with your lens. :)
Click to expand...
I'll take your word for it at the moment. As I say until I can get out in good light I can't tell much. I am sure I am looking for problems that are just not there. :D
 
Chaz Photos said:
think that is true of early ones but not so on new ones
Click to expand...
I have just got it so I guess it's a new version. Turning IS off does appear to have had a small effect for the better at f2.8.

....as for sharpening..I didn't add any here as I wanted to show you guys the pics as they came off the camera in case there is anything that you can spot that sharpening could mask.


Andy S
 
Doesn't really look like a fair test to me - try it again outdoors in better light - remember that under tungsten light, things will appear softer anyway due to the relative lack of blue and green wavelengths...
(those old enough to remember will recall that older lenses used to have a seperate IR focusing index - the red end of the spectrum is slightly OOF compared to the green and blue)...
 
Agree with CT. Nothing wrong with the lens on this evidence. Sorry to say bud, but it's your technique that needs sharpening up ;)

Accurate focus is essential with DoF measured in mms. Shake-free - a tripod is no guarantee of that, and IS on is unlikely to do much on a tripod, but shouldn't do any harm either. Plus a bit of sharpening in post.
 
Also the second set look soft because of noise. Maybe try again in daylight, keep ISO to 400 or lower, shoot jpg - should give what you're looking for :)
 
As a matter of interest, check the write up for this lens on PHOTOZONE, especially the verdict.
 
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