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On this focus thing


Mozzytheboy e2
4 702 3 United Kingdom
25 Jul 2013 2:04PM
Every time I ask a question, I feel pangs of guilt and so hope and pray you don't think "Oh no, not him again.' Just thought I would mention that in case you didn't think I appreciated how wonderful it is that people give up their time to offer advice.

Question is on focus really. I think I am holding the camera steady and I believe that I am. On my Canon 500D I have the 24-105 L series which since purchase I've remained rather disappointed. I seem to get better and clearer images with the 55-250 which to-date is my favourite. When I take in RAW then open in say PSE9, it looks Ok but as soon as I start increasing the size the focus is gone. Tis a long winded way of asking when pressing the increase size button, how many should I be able to do before blur?

I'm using evaluative metering, mostly ISO 200, AV settings with auto WB. On focus i use the one central point which gives me a message of manual selection over auto selection. I use auto focus on the lens as much as possible as I wear vari-focal spectacles and on the occasions I have tried manual I seem to fail miserably. I recently have tried using what I have to take some images of the bees. Not a one out of over a hundred was usable, each was slightly off. Could I have problem with my camera body?

I do have very bad arthritis and find a tripod almost a nuisance at times; it never seems to be in the right spot.

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25 Jul 2013 2:20PM
In my opinion the results from the L lens should far outweigh the 55-250, so that leaves you with a technique issue.

Your choice of ISO 200 could be your problem. In Av mode this would force a lower shutter speed, which could be leading to blur being caused at the taking stage. You can override that by increasing your ISO to ISO 640 - but also, what aperture are you set at?? If f11 then you really need to open up to f4 or f5.6 to increase your shutter speeds and so stop shake at the taking stage.

The way to tell if you have a body issue is to shoot something with a ruler beside it, marked at an appropriate spot, and focus on that. If you see it on the screen and the focus point is different from your marked spot, then you have a body focussing issue. This can be adjusted in camera on some - not sure about yours!

Re size on screen. Everything will blur as you start to increase the size. The important point is to try and establish where, and how accurately your camera is focussing, so do the ruler test.

Re Tripods - you may benefit from a monopod and a ball head, which would help with your support but still remain mobile enough when shooting.
mikehit e2
5 7.1k 11 United Kingdom
25 Jul 2013 2:23PM

Quote:but as soon as I start increasing the size the focus is gone

Do you mean when you look at it 100% view? The answer is 'don't' - to check sharpness you only really need to use 50% view or maybe less.

Bees in flight are very difficult to get pictures of because they move surprisingly quickly and I guess you are trying to get them as large in the frame as possible in which case you will be quite close and the depth of field gets horribly shallow. So it may just be that the camera AF can't keep up with the little critter. Try something slower and see how it goes.

The best way to check the camera focus is to use your tripod to remove as many variables as possible (especially camera movement) - fix it securely, use LiveView and a remote release (or 10-second shutter timer). My preferred method is to put a stake in the lawn and focus near the bottom of the stake - the blades of grass will show you how far out the focus is.
Mozzytheboy e2
4 702 3 United Kingdom
25 Jul 2013 2:30PM
Fantastic help as always. Thank you both.
lemmy e2
7 2.0k United Kingdom
25 Jul 2013 5:17PM
Keep an eye on the magnification on screen. Any picture will look unsharp at 200%.

Definitely eliminate user error before blaming equipment. You cannot test focusing meaningfully hand held. A tripod is essential.

Stand a can of coke or beer, whatever on a table and line your camera up on it on a tripod. Using live view, not the viewfinder, focus the lens on a detail, the bar code is ideal. Live view because this reads directly off the sensor. Take your picture using delayed action. Now take the camera off live view and focus using the viewfinder.

if both of theses are sharp, the problem lies with you. If the shot focused through the viewfinder is not as sharp as the one on live vew, your lens needs calibrating to the camera. Most cameras have a way of doing this without resort to a service station.

If neither are sharp (highly unlikely), your lens is duff. Or, you are expecting too much when you magnify the image.

But remember, any testing done off a tripod or similarly solid mount has no validity whatsoever.

By the way, it is difficult to think of a worse way of judging equipment than by pictures of fast moving, unpredictable and tiny insects Wink

And sorry about your arthritis - I have a friend who suffers from it, joke at all. I have a littler Manfrotto table top tripod which is wonderfully effective. Something like that might help you?
Mozzytheboy e2
4 702 3 United Kingdom
25 Jul 2013 5:42PM
Twice now I lost the lot everything I typed. Just hanging when I try to upload a sample image. Sorry
llareggub e2
4 757 United Kingdom
25 Jul 2013 6:46PM
The maximum magnification of the 24-105l is 0.34x so if your bee is a 1cm across and you are at your minimum focus distance it will only fill 3.4 mm of your sensor which is only 22.3mm wide., just 14%... The chances of being at minimum focus distance with a bee in flight is incredibly low so that figure reduces greatly, my guess is that even touting a 1DX with its tremendous AF system you are gonna struggle to get that shot with that lens.

As other have mentioned, try taking some less 'taxing' shots that are within the capabilities of both the cameras AF system and the lenses focal length and see where you go from there Smile
lemmy e2
7 2.0k United Kingdom
25 Jul 2013 6:57PM

Quote:joke at all


Typo - that should read 'no joke at all' obviously.
Mozzytheboy e2
4 702 3 United Kingdom
25 Jul 2013 9:41PM
Just a thought; I never use live view as it drains the batteries too much. Is it really that more accurate than using the viewfinder in manual or auto focus?

Thanks.
mikehit e2
5 7.1k 11 United Kingdom
26 Jul 2013 12:25AM
Live View is only valuable for manual focus and when you use the magnified view, and as such it only really works for static subjects.
26 Jul 2013 1:00AM
Some technical advice from Canon. Not all of this can be useful for an owner of an EOS without AF micro-adjust, but may give you some lines to think along. Another thing I noticed looking through your portfolio ( some great images there!) is that you used, and probably use, a compact sensor camera. The comparison in sharpness will be not in DSLRs favour - for smaller sensors dictate substantially shorter focus lens with DOF "from here to infinity". I reckon you could gain a lot from getting a reasonably cheap 40 or 50mm prime for your DSLR - as zooms are hopeless image quality wise at their closest and furthest extremities. And I would join other members' advice on view zoom use - pixel peeping always leads to disappointment. There are too many pixels in modern cameras to pay attention to each of themSmile Check the picture sharpness at the scale you are going to show it to the others. As for me - when processing RAW I use different sharpening values for big prints and Internet - sized images. And RAW needs to be sharpened - sharpening is not switchable off altogether (only adjustable) in JPG for a good reason.
Gundog e2
1 624 Scotland
26 Jul 2013 10:38AM
Mozzy,

I am guessing that this is not a focus problem at all but, perhaps, just an attempt to make a very small subject large by over-cropping.

Wee test - if you view the entire frame (without cropping) so that it fills or almost fills your PC monitor, do you still think it lacks sharpness?
Mozzytheboy e2
4 702 3 United Kingdom
26 Jul 2013 12:10PM

Quote:Mozzy,

I am guessing that this is not a focus problem at all but, perhaps, just an attempt to make a very small subject large by over-cropping.

Wee test - if you view the entire frame (without cropping) so that it fills or almost fills your PC monitor, do you still think it lacks sharpness?



No it would seem fine even putting my nose to the screen. Is it therefore me?
llareggub e2
4 757 United Kingdom
26 Jul 2013 12:49PM
I don't thing it is you, you should expect to be able to take a 'healthy crop of an image and still see reasonable sharpness with a lens of the quality of the 24-105L and your Canon 500D... The 500D shares the same processor and same sensor as my 50D and this is the sort of sharpness I am seeing from a 100% (600X400px) crop straight from the raw, no noise reduction and no sharpening.

bjp1194.jpg



And this is post sharpening and noise reduction (original picture was taken at ISO800 @ f9 with a Sigma 50mm f2.8 macro

bjp1194-sharpened.jpg

llareggub e2
4 757 United Kingdom
26 Jul 2013 12:51PM
For reference this is the source image Smile

bjp1194-full.jpg


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