Can't seem to focus!

topcat374

Hi everyone,

I'm in the middle of playing around with my 50mm f/1.8 and have run into a problem! I'm photographing glass chess pieces, lit with a torch in an otherwise dark room (see pic below). I've auto-focussed on the cross on the top of the king, switched to manual focus, re-composed the picture and then triggered the shot with a remote infra-red sensor. I'm using a D50 so there's no mirror lock-up function. Aperture is 1.8, shutter speed is 1/25 and ISO is 200.

What I can't understand is why the top of the cross is not in crystal clear focus?!?! It's driving me mad! Is this down to camera shake (in which case, with no mirror lock up function, I think I've done as much as I can) or is something else at work here? Too much light bouncing off frosted glass perhaps? Can ANYONE help?!?!

Thanks in anticipation,
Craig

DeVerm

Test with a little piece of colored tape attached to the face of the cross. Repeat with different lens. Repeat at very high ISO with short shutter time.

My Canon can't autofocus on that but manual works good, even without mirror lock up. The high ISO with short shutter would test your theory that it is the mirror.

ciao!
Nick.

topcat374

DeVerm wrote:

Test with a little piece of colored tape attached to the face of the cross. Repeat with different lens. Repeat at very high ISO with short shutter time.

My Canon can't autofocus on that but manual works good, even without mirror lock up. The high ISO with short shutter would test your theory that it is the mirror.

ciao!
Nick.

Thanks for advice Nick. Will go and test that now...

topcat374

DeVerm wrote:

Test with a little piece of colored tape attached to the face of the cross. Repeat with different lens. Repeat at very high ISO with short shutter time.

My Canon can't autofocus on that but manual works good, even without mirror lock up. The high ISO with short shutter would test your theory that it is the mirror.

ciao!
Nick.

Have tried tape and high ISO (1600 leaving a shutter speed of 1/100) to no avail (see pic below). I even scrapped the composition of the photo and kept the centre focal point of the camera on the tape and it still isn't in focus. Will try another lens next to see if that makes any difference but now getting late here so may have to wait until tomorrow!



Will keep trying. Any other advice gratefully received!

PhotoLasVegas

I'm hoping this isn't so simple that others are just missing it or maybe I'm pointing out the obvious...

Look CLOSELY at your first photo.. there IS a sharp focus, but it's not on your intended focus point.

The DOF of that lens is VERY VERY VERY shallow so likely when you are re-composing you are moving the focus point. It's also slightly possible that when you click over to "manual" focus (presumably to stop the camera from re-focusing?) you are slightly bumping the focus mechanism?

What I'd do is (assuming Nikon has this), compose the shot and then select your focus point via the internal focusing grid.

When we do weddings, we do a lot of very shallow DOF "ring shots" and we do this hand-held on the fly.. we have our camera set to focus on the center typically, but when we do ring shots, we change our AF point inside the camera and it works great.

topcat374

PhotoLasVegas wrote:

I'm hoping this isn't so simple that others are just missing it or maybe I'm pointing out the obvious...

Look CLOSELY at your first photo.. there IS a sharp focus, but it's not on your intended focus point.

The DOF of that lens is VERY VERY VERY shallow so likely when you are re-composing you are moving the focus point. It's also slightly possible that when you click over to "manual" focus (presumably to stop the camera from re-focusing?) you are slightly bumping the focus mechanism?

What I'd do is (assuming Nikon has this), compose the shot and then select your focus point via the internal focusing grid.

When we do weddings, we do a lot of very shallow DOF "ring shots" and we do this hand-held on the fly.. we have our camera set to focus on the center typically, but when we do ring shots, we change our AF point inside the camera and it works great.

Hi there,

Firstly, please do post the very simple and obvious! I'm learning lots about photography in theory but am still very much a noob when it comes to putting it into practice!!! ALL advice is more than welcome!!

Secondly - you have a very good point!! This is a new lens and previously the lowest f/stop I had was 3.5 and then only if shooting at 18mm - nothing like the finese of this lens! The second shot I posted is with the central focal point on the tape (no re-composition) and it still wasn't in focus but tbh I've lost concentration now(!) and am not sure if I did everything right that time so will set it up again tomorrow night and have another go. I'd really like to get to grips with how to control this kind of shot so will keep posting here until I crack it!!

Thank you again for you advice:)

Art Scott

If you have a tripod do a shot with camera on tripod and no re-positioning....to see if it might just be a bad lens or faulty focusing.......

Also try a black piece of tape if you have it.....that camera might need all the contrast it can get to focus properly.

Good Luck

Scott_Quier

topcat374 wrote:

Hi everyone,

I'm in the middle of playing around with my 50mm f/1.8 and have run into a problem! I'm photographing glass chess pieces, lit with a torch in an otherwise dark room (see pic below). I've auto-focussed on the cross on the top of the king, switched to manual focus, re-composed the picture and then triggered the shot with a remote infra-red sensor. I'm using a D50 so there's no mirror lock-up function. Aperture is 1.8, shutter speed is 1/25 and ISO is 200.

What I can't understand is why the top of the cross is not in crystal clear focus?!?! It's driving me mad! Is this down to camera shake (in which case, with no mirror lock up function, I think I've done as much as I can) or is something else at work here? Too much light bouncing off frosted glass perhaps? Can ANYONE help?!?!

Thanks in anticipation,
Craig

Art, as usual, seems to have nailed the problem. At the distance you are working, the focus-and-recompose technique is never going to get you a plane of critical focus where you want it and your wide aperture is going to ensure your DOF is not going to be wide enough to cover the error.

Read one or more of the following:

• How A Commonly-Used AF Technique Causes Focus Errors
• Focus and Recompose Exposed
• The Pitfalls of the Focus-Recompose Technique

angevin1

In both photos, but esp. the first, the focus point seems to be well in front of the desired piece! Being new-ish, I'm certain you'll read Scott's suggested info, but basically with the aperture you chose your Depth of field is small, especially at that close distance. Recomposing from that distance and with that aperture is a lesson in frustration and I am uncertain why you would need to do that.

If I took that shot with my 50mm 1.8 @f/1.8 I could easily imagine the top of the chosen piece being in focus and the bottom not in focus, just due to the Depth of field~

cmason

I am not sure your physical distance to the subject, but if it was about 3ft, then DOFMaster.com says the range of focus is 0.07 ft! (.8 in)

Depth of field
Near limit 2.97 ft
Far limit 3.04
Total 0.07 ft

http://dofmaster.com/dofjs.html

So before you consider the problem with the lens, try focusing with an alternate focus pt, with no recompose.

topcat374

Okay - am learning all the time here so apologies in advance of I just don't 'get it'!!!

First of all - the bits of info I didn't put in the original post but I now realise would have been helpful(!!):

Distance from subject was about 2 feet
Camera was mounted on a tripod
Lens is new and has been working well in other situations so don't think it's faulty (couldn't guarantee it though!!)

cmason wrote:

I am not sure your physical distance to the subject, but if it was about 3ft, then DOFMaster.com says the range of focus is 0.07 ft! (.8 in)

I've put the new info into DOFMaster.com (thanks for the link - didn't know this existed!) and it tells me my DOF is 0.02ft (converted to 6mm so I can understand it!!) This does seem ridiculously narrow so maybe I should learn to walk before I try to run! The second picture posted is using an alternate focal point but by then I'd lost concentration and don't even think I got the shutter speed right so need to try that again!

angevin1 wrote:

Recomposing from that distance and with that aperture is a lesson in frustration and I am uncertain why you would need to do that.

So I'm discovering!! As for why I'd want to do this...really just because I've got a new lens and thought it would be a useful exercise! Tbh, I originally was shooting with bounced flash and turned off the room lights because they were casting too many shadows. I only got the torch out so I could see what I was doing with the settings on my camera so the whole thing really is quite impromptu but good fun all the same!! I think it may be a good idea to open up the DOF and then gradually narrow it down to something that works...what do you think?

Art and Scott - thanks for opening my eyes to the pitfalls of focus and re-compose. I use this technique all the time and hadn't really considered any issues with it before!! I will try a bit of black tape, use a different focal point inside the camera and NOT recompose!

Hope to have another fo at this tonight so will post a new pic again after that if you can all bear with me!! Have a missed anything?!

cmason

FWIW, I think its a cool shot, so keep trying!

topcat374

cmason wrote:

FWIW, I think its a cool shot, so keep trying!

Thanks for the encouragement - it's spurred me on:) So...

50mm, f/3.2, ISO 200, 2 feet away, auto focus using the uppermost point on my internal grid, converted to black and white in elements. Had to change the angle to ensure the plane of focus issue was sorted out (wouldn't have had to if I'd had an AF point a couple of mm higher on the internal grid - or was better at manal focus!). Whatya think?

Art Scott

that is better.bow

PhotoLasVegas

Almost perfect with the focus, but liked the original composition (from above) much better...

00SS

PhotoLasVegas wrote: »

Almost perfect with the focus, but liked the original composition (from above) much better...

+1

That nifty 50's sweet spot is at 3.2, it has a very shallow dof at 1.8 (as been said). I started with the same gear as you, keep at it and you'll get better

topcat374

Thanks for the advice and support everyone - REALLY appreciate it:) I'll have another go at the shot from above as I did like that angle too and kind of feel like I've been forced into the current angle (although I'm really pleased with how that one has turned out).

Thanks again. I'll post an update after I've had another go:)

Craig

ckaspar

No pro here but can you put something temporarily where you want to focus to be, setup the camera and focus, turn on MF then remove the temporary focus point then shoot? That might give you the angle you want.

DeVerm

I still don't understand it: AF should have no trouble with the piece of tape added. Also, with manual focus it should not be a problem either.

It might be that you can't see if it's in focus through the viewfinder. I have actually bought a new small laptop to use for tethered shooting with live-view enabled. This locks the mirror up and it allows me to zoom in to check focus on a 13" LCD screen... all before taking the shot.

Before I got my 7D, I just made a whole series of shots using manual focus and changing it as little as I could every shot.

When using the piece of tape and AF doesn't work, the lens might need calibration may be?

Edit: ah, re-composing, yes, that could kill focus. I just never connected a tripod with re-composing techniques...

ciao!
Nick.

WillCAD

PhotoLasVegas wrote: »

I'm hoping this isn't so simple that others are just missing it or maybe I'm pointing out the obvious...

Look CLOSELY at your first photo.. there IS a sharp focus, but it's not on your intended focus point.

The DOF of that lens is VERY VERY VERY shallow so likely when you are re-composing you are moving the focus point. It's also slightly possible that when you click over to "manual" focus (presumably to stop the camera from re-focusing?) you are slightly bumping the focus mechanism?

What I'd do is (assuming Nikon has this), compose the shot and then select your focus point via the internal focusing grid.

When we do weddings, we do a lot of very shallow DOF "ring shots" and we do this hand-held on the fly.. we have our camera set to focus on the center typically, but when we do ring shots, we change our AF point inside the camera and it works great.

Ya know... I had exactly the same thought when I read the original post and looked at the image, and when I read your response, I thought, "Yes! I actually got one right for a change!"

Topcat, I liked the composition of the original shot better, but I prefer the color in the second shot. Is that the same board in both shots, or is it just that the different angle made the wooden squares of the board less brown and more silver/gray?

topcat374

DeVerm wrote: »

I still don't understand it: AF should have no trouble with the piece of tape added. Also, with manual focus it should not be a problem either.

It might be that you can't see if it's in focus through the viewfinder. I have actually bought a new small laptop to use for tethered shooting with live-view enabled. This locks the mirror up and it allows me to zoom in to check focus on a 13" LCD screen... all before taking the shot.

Before I got my 7D, I just made a whole series of shots using manual focus and changing it as little as I could every shot.

When using the piece of tape and AF doesn't work, the lens might need calibration may be?

Edit: ah, re-composing, yes, that could kill focus. I just never connected a tripod with re-composing techniques...

ciao!
Nick.

Hi Nick,

I think the main issue with AF is that I can't seem to line up an AF point with the top of the cross AND compose the shot as I want it to fit all of the pieces in. The AF point at the top of the internal grid lines up lower down the king. My original solution of focussing on the top of the cross and then re-composing was evidently flawed(!) and I couldn't seem to find an angle where the top of the cross and the AF point did line up (except for the last shot I posted of course!). My manual focus skills are not so good but your idea of taking a series and just adjusting marginally each time could work for me so I'll give that a go.

(The AF focus on the tape (second posted shot) didn't work but it had got so late that I couldn't swear to having done that right!!)

topcat374

WillCAD wrote: »

Ya know... I had exactly the same thought when I read the original post and looked at the image, and when I read your response, I thought, "Yes! I actually got one right for a change!"

Topcat, I liked the composition of the original shot better, but I prefer the color in the second shot. Is that the same board in both shots, or is it just that the different angle made the wooden squares of the board less brown and more silver/gray?

The original colour of both shots is about the same but I've converted the last image to mono. The main difference I got between the angle of the 2 shots was the reflection, which was much more pronounced in the level shot than it was in the shot from above. I'm determined to try from above as well now though as it means I can have the king completely surrounded which I think tells a different story to having a gap...

WillCAD

You know, not being really good with all this sort of thing - I'm a ham-handed amateur, at best - my solution would probably be simpler.

Instead of trying to manipulate the focus, I would take the shot with a wider DOF, so that more of the pieces and more of the board would be in focus. Then, it wouldn't be such a Swiss-watch-precise necessity to get your DOF at just the right distance from the lens. Wider DOF would require changes to the aperture, the focal length, and the distance to subject. Changing focal length would require you to change lenses.

If the calcs posted earlier in this thread are accurate, and your DOF is really only 6mm, then it will be impossible to achieve the effect you're looking for using that lens at that distance to subject. You need a wider DOF to get those pieces in focus, which means you have to pull the camera back and zoom in, so you won't be able to compose the shot the same if you stick with that 50mm.

I'd swap lenses for the 55-250 you have listed in your sig, move the tripod back farther, zoom in, and recompose. With greater distance to subject, you'll get a wider DOF, and more of the pieces will be in focus. Then you can play with exposure a little to tweak brightness, aperture to tweak DOF, and play with the image in Photoshop to blur the board a little more if it comes out too sharp for the effect you're trying to achieve.

Svennie

Maybe you could move your camera back a little, until the top AF point lines up with the chess piece. Take the photo, then crop the image back in PP to get the composition you like.

Art Scott

does the D50 have a focus lock button.....that is a button that after the auto focus focuses you depress the button and move the camera wherever you want.......

I do not have time to down load the D50 manual to read it....getting ready to drive to Lexington Ky to shoot the city........

topcat374

Thanks everyone - will have a play with DoF and re-positoning - there must be a way of lining up that top AF point!! Am keen to stick with the 50mm though as I'm really trying to learn that lens at the moment (will swap lense if I really can't get the shot with that one:))

Art - yes, the D50 has a focus lock which I would normally use instead of switching off the manual focus but avoided it this time as I wanted to minimise camera shake so wanted to be 'hands-off'. I assume it wouldn't reduce the focus - re-compose issue that Scott refers to though...?

Will try for another attempt this evening. Got busy putting up our new tent in the back garden yesterday and then prepping for camping in the next couple of weeks. Now own a huge tent (Outwell Vermont L if anyone's interested!) and very little to put in it! Mind you - I have my wife, 2 kids and my camera...not sure what else I need!!!

DeVerm

Well, if you can't select a focus point that high up the viewfinder and want to use AF, I agree with the other poster about backing up a bit with the tripod until you can and crop it on the computer.

But I would use manual focus and adjust until I get it right. That's the good thing about digital ;-)

cheers,
Nick.

topcat374

Okay...3rd attempt:)

I think I've managed to crack the focus issue (from above) using the solution suggested (i.e. move back a little and then crop in PP) and by closing the aperture down to F/5.6 to extend the DoF...



I then also played with the other viewpoint I posted earlier...





I've found the latter shot much more rewarding but I think that may be because I can no longer see the wood for the trees! I've learnt SO much from this as an exercise though, about DoF, focus and the effects of very minor changes to lighting in particular!!

I'd very much appreciate feedback if you still have the patience to give it (whether you've already contributed to this thread or not). I also just want to say a big thank you for the feedback so far - it's really spurred me on to try to get the shot right (I do have a tendency to give up from time to time!!).

Craig

WillCAD

I love the new shots, particularly the first one.

topcat374

WillCAD wrote: »

I love the new shots, particularly the first one.

Thanks WillCad - much appreciated:)

Svennie

Very nice

#2 of the new set is my fav. Cool shoots