Beginner Trying to get better sharpness/detail - what can I do to improve?

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Amanda
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#1
Hello experts?

I've been worried about the sharpness I've been getting on my D7100 and I wondered if it was me or the equipment.
I tried to do some tests AF using some charts and there seems to be no real issue there in terms of front or back focus. AB edited -7775.jpg
However, when I was doing these tests I saw the following (see pic - a crop of full image) -
- Despite shooting at 100 ISO (slow shutter speed, but on tripod and with remote, 14 bit RAW), I think that the bits 'in focus' don't really look super 'sharp'.
- Furthermore, the lines in front of the focus look purple and the lines behind look green - this was on more than one of my lenses - the 50mm 1.8g was the worst.

Q - Why isn't the image sharper, or am I at the limitation of the D7100 ?
Q - Is this purple/green weirdness normal?

Cheers
Amanda
 

TCR4x4

Wishes he had a couple more Inches
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7,997
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Tom
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#2
Purple/green is chromatic aberration and is perfectly normal. Is usually worse at the extremes of aperture. Try opening the aperture up a bit, you'll find most lenses perform their best a few stops above their widest. They the 50mm at F/2.8 and you should see a marked difference.
 
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David Williams
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#3
Hi Amanda

The angled chart is not a good way to test focus. The focus points on a DSLR are either straight lines or cross shaped and presenting a tilted target means you can never be exactly sure where it is focusing.

You need a perfectly vertical target with this tilted scale alongside do you can use it to judge front or back focus.

You need a DIY version of this http://www.the-digital-picture.com/Reviews/Datacolor-SpyderLensCal-Review.aspx

The purple green weirdness is chromatic aberration, which is worst with sharp light/dark boundaries as you have here. Can be corrected in post processing.

HTH

David
 
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Richard
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#4
David, I think that is a crop of a larger angled chart. The camera will focus on the black bar you see at the right of the frame (it is much bigger in reality) then you read the front/back points off the scale.

So kind of an all in one version of the lenscal, and it works remarkably well.
 
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Amanda
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#5
David, I think that is a crop of a larger angled chart. The camera will focus on the black bar you see at the right of the frame (it is much bigger in reality) then you read the front/back points off the scale.

So kind of an all in one version of the lenscal, and it works remarkably well.
Yes, it's a crop of an angled chart.

Hi Amanda



The purple green weirdness is chromatic aberration, which is worst with sharp light/dark boundaries as you have here. Can be corrected in post processing.

HTH

David
I tried in lightroom and the purple seemed to go but not the green - i guess I need to check how to do it properly.

However, my main issue is the detail in the 'in focus' bit - is that as good as it gets?
 
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John
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#8
Does AF work better in live view?
It's potentially more accurate because (as I understand it) it adjusts until the image on the sensor is as in-focus as it can be, kind of like what you see is what you get. The phase detect AF relies on the AF system being properly calibrated and adjusted and there is potential here for error/misfocus (which AF fine tune systems are meant to overcome).

Essentially, the live view AF will give you the sharpest, most in-focus result - if you're not getting the same result with PDAF then you may want to look into the AF fine tune settings.
 
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#9
It's potentially more accurate because (as I understand it) it adjusts until the image on the sensor is as in-focus as it can be, kind of like what you see is what you get. The phase detect AF relies on the AF system being properly calibrated and adjusted and there is potential here for error/misfocus (which AF fine tune systems are meant to overcome).

Essentially, the live view AF will give you the sharpest, most in-focus result - if you're not getting the same result with PDAF then you may want to look into the AF fine tune settings.
But it looks like focusing through the viewfinder is fine when I tested - i.e., it focuses where it's supposed to (see image).
What I'm concerned about is the detail of what's in focus? (or am I expecting too much from my camera?)
 
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#10
But it looks like focusing through the viewfinder is fine when I tested - i.e., it focuses where it's supposed to (see image).
What I'm concerned about is the detail of what's in focus? (or am I expecting too much from my camera?)
I'm sure it is focusing where it is supposed to, the question is whether it is focused accurately or not, could it be more in focus compared to the live view equivalent?
 
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#11
I'm sure it is focusing where it is supposed to, the question is whether it is focused accurately or not, could it be more in focus compared to the live view equivalent?
Now I'm bamboozled, I don't understand; if it's focused where it's supposed to, doesn't that mean it's accurate?
Sorry, as a village idiot, I think I've reached my understanding limit...
 
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John
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#12
It just means that the PDAF system has decided that the image is as in-focus as it can be. It might not actually be, though - it all relies on the correct calibration of the PDAF system done at the factory. If you're getting slightly out of focus images when the camera is saying it is in focus, then it's not focusing accurately, despite what the green dot confirmation may indicate. That's why I suggest comparing against live view AF - if this is pin-sharp compared to the phase detect AF, then some AF fine tuning may be needed. They are totally different AF systems, the AF fine tune only affects the PDAF.
 
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David Williams
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#13
What I'm concerned about is the detail of what's in focus? (or am I expecting too much from my camera?)
Hi again.

I think that you probably are expecting a bit too much, I have just seen your camera is 24MP on a crop sensor, the original image from your first post must be huge!.

Unless you are going to spend your whole time printing images feet across then you will be very pleased with the images from your camera.

Having been a keen photographer from the days before digital I have to keep reminding myself that clicking "100%" and pulling a face because the image on the screen is not pin sharp does not help much in progressing my photography.

Every digital capture system has its limits and as long as your camera is performing to specification then just carry on a stay away from the 100% button :)

And as said above the very best focus method is to use live view, zoomed in to 10X if possible.

HTH

David
 
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Amanda
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#14
It just means that the PDAF system has decided that the image is as in-focus as it can be. It might not actually be, though - it all relies on the correct calibration of the PDAF system done at the factory. If you're getting slightly out of focus images when the camera is saying it is in focus, then it's not focusing accurately, despite what the green dot confirmation may indicate. That's why I suggest comparing against live view AF - if this is pin-sharp compared to the phase detect AF, then some AF fine tuning may be needed. They are totally different AF systems, the AF fine tune only affects the PDAF.
Sorry, the point I'm making is that I've checked that the viewfinder AF is OK - as in the chart above.
It's the detail of what's in focus that I'm wondering about.

Saying that, I had no idea that the live view and viewfinder focus were different - will read the chapter on that in my 'D7100 for dummies'. :)
So far it says that Live view focus is slower - in that case, I don't think I'd ever use live view for what I do.
 
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Amanda
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#15
Hi again.

I think that you probably are expecting a bit too much, I have just seen your camera is 24MP on a crop sensor, the original image from your first post must be huge!.

Unless you are going to spend your whole time printing images feet across then you will be very pleased with the images from your camera.

Having been a keen photographer from the days before digital I have to keep reminding myself that clicking "100%" and pulling a face because the image on the screen is not pin sharp does not help much in progressing my photography.

Every digital capture system has its limits and as long as your camera is performing to specification then just carry on a stay away from the 100% button :)

And as said above the very best focus method is to use live view, zoomed in to 10X if possible.

HTH

David

Thanks, that''s kind of the answer I was hoping for. I think that I am expecting too much.
I think that seeing so many amazing pictures on t'internet makes jealous that I can't do that yet!
 
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Bazza
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#16
I have one of those spider lens cals thingies, to use one the camera lens has to be parallel to the target, great, but what you are not told is what distance the camera should be from the cal to check properly. It is not even mentioned on the instruction, so although in principle its a good idea, in reality its useless. for each lens the target cal need to be closer or nearer, and if using anything but a prime lens using a variable mm lens it is nigh impossible to get exact sharpness
 
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#17
Thanks, that''s kind of the answer I was hoping for. I think that I am expecting too much.
I think that seeing so many amazing pictures on t'internet makes jealous that I can't do that yet!
Can you post a link to an example of a photo you think has amazing sharpness? Sometimes it helps to see what you're aiming for.

I think we all get a bit obsessed with sharpness for a while when we're starting out. Thing is, oftentimes we are comparing our work to images that have quite a lot going on behind the scenes. Perceived sharpness is down to the lens and to a lesser extent the camera, yes, but lighting (quality and direction) and post-processing play a huge role too.

Your d7100 is perfectly capable of taking photos like almost anything you see online. The difference in image quality for online viewing between your d7100 and any higher spec digital camera will be nigh on imperceptible, all else being equal.
 
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paul
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#18
if you want sharpness, then get a sigma dp merrill, they really are a step or two above bayer (normal digitals camera's), and on a per pixel basis nothing matches them
 
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#23
Okay, there's nothing remarkable going on there beyond basic technique. You should be able to achieve this sort of image easily.
How about posting one of your images that you feel is suffering from lack of sharpness. Not a test shot and not 100% cropped.
You said earlier that live view focus was not good for your kind of work. I wonder if maybe you're shooting some kind of action? This can present distinct focussing challenges for beginners.
 
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Mike
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#24
All missing a blindingly obvious point here are you shooting in raw or jpeg if raw it will need sharpening after it is uploaded to your computer lightroom/detail/amount 40/radius 1.4 is a good start point hth mike
 
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