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Why am I losing focus?

losing focus

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11 replies to this topic

#1
Tony

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First of all I hope this is in the proper section.  I have noticed that when using my AFNikkor 28~105mm f3.5~4.5D IF Lens when shooting flowers, that the center of the flower is sharp, but only one or two of the petals are also sharp.  The others are out of focus.  There is a good example in the Gallery under Recent Images by Malice on the bottom left hand corner.  Interesting that I do not experience this problem with my shorter AFNikkor 35~70mm non D lens and my AFNikkor 35~80mm D lens.  I have double checked the settings for focus and everything seems to be set properly when following the steps laid out in the Instruction Manual.  I wonder if the cause could be that the petals are farther away from center than is revealed in the viewfinder or focus area.

 

Thanks in advance for any comments/suggestions/solutions offered.  I will post my own example here.  As is seen the two bulbs and the one or two leaves above them are in focus, but not anything else.  It just seems to be a strange focus pattern when everything in the viewfinder appeared to be in focus.

 

Antonio 

 

Ooops!  Here are the particulars.  Nikon D70 with AFNikkor 28~105mm f3.5~4.5D IF Lens.  1/80s, F4.5 @105mm., no flash. ISO @ 200.

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  • DSC_2372.JPG


#2
Thumper

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It sounds like you are shooting with the aperture open wide, which will make your depth of field more shallow.  Things on the same plane as what you are focused on will be in focus while other things will not, even if they do not appear (initially) to be on a different plane. 



#3
mikew

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You dont say what ISO and with the D70 you need to be careful you dont go too high, if you go up one stop at a time with it and stop the lens down by 1 stop each time,see where that takes you.



#4
Tony

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It sounds like you are shooting with the aperture open wide, which will make your depth of field more shallow.  Things on the same plane as what you are focused on will be in focus while other things will not, even if they do not appear (initially) to be on a different plane. 

Hi Thumper, thank you for your input.  Okay, so this means that by stopping the lens down one or two stops I will need to use a slower shutter speed, which is fine since I am now using a tripod 99% of the time.  I suppose the old bracketing technique will have to come into play since I do not want a very deep depth of field.  This confirms my suspicions that I will have to use the D70 in M from now on.  Again, many thanks.

 

Antonio


You dont say what ISO and with the D70 you need to be careful you dont go too high, if you go up one stop at a time with it and stop the lens down by 1 stop each time,see where that takes you.

Sorry about that I continue to forget that for some reason the EXIF data does not come forward.  I do have the particulars listed now.  ISO @ 200.

I tend to keep it at 200 because I really dislike having to deal with Noise.  Even at ISO 200 I still have to deal with Noise, but not as much as I would with higher ISO.  Thanks for your input.  I just do not get why the difference when using my shorter telephoto lenses. I have had my share of experiences with telephoto lenses and I do know that they can be touchy at times. 

 

Antonio



#5
Merco_61

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The 28-105 gives a maximum magnification of 1:2, the 35-70 1:4.4 and the 35-80 in the region of 1:4 if I remember correctly. With larger magnification comes a shorter DOF. I don't know how close this was taken, but if you are in the Macro mode of the 28-105 you can expect a shorter DOF than otherwise.

The reason the shallow DOF don't show too well in the viewfinder is that the focusing screen in the D70 is optimized as a composition aid, not for precise focus.



#6
Tony

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The 28-105 gives a maximum magnification of 1:2, the 35-70 1:4.4 and the 35-80 in the region of 1:4 if I remember correctly. With larger magnification comes a shorter DOF. I don't know how close this was taken, but if you are in the Macro mode of the 28-105 you can expect a shorter DOF than otherwise.

The reason the shallow DOF don't show too well in the viewfinder is that the focusing screen in the D70 is optimized as a composition aid, not for precise focus.

Peter I just checked and the photo was taken at 105mm.  Thank you for your input, as always, very educational.  Much appreciated.

 

Rgds,

 

Antonio



#7
dem

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The tripod is not going to help much when shooting flowers outside because they move in a slightest breeze. You need more light. A quiet, slightly overcast morning is the best.

Keeping aperture between f/11 and f/22 will give you a deep depth of field - the higher the f-number, the more of the flower will be in focus. Doubling the f-number will also double the depth of field. f/16 is the sweet spot as it gives you 50% more DoF than f/11, is not as soft as f/22 due to diffraction and still allows for shutter speeds about 1/100s at a low ISO.

With any lens you can always gain a bit of depth of field at the expense of magnification: just step back or zoom out a little so the framing is less tight.

#8
Ron

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All good suggestions above. However, when I look at that photo the first thing that pops into my head is that it needs a small amount of off camera flash.

 

Depth of field is definitely a problem but if you close down your aperture to gain depth of field, you open up another can of worms... namely camera shake or noise from bumping the iso to high in order to compensate. Use a speedlight and ta-da!  As an added bonus, flash serves to separate your subject from the background and brighten things up a bit. As it is, even with all that color, the image looks a bit flat and drab.

 

If you have a TTL flash, cool. Let it do it's thing. But even if you have a flash that only supports AUTO (on the flash) set it to that, set your camera to F/16 @ whatever your sync speed is and shoot. As long as you stay inside the AUTO range of the flash you should be good to go.

 

--Ron



#9
Tony

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The tripod is not going to help much when shooting flowers outside because they move in a slightest breeze. You need more light. A quiet, slightly overcast morning is the best.

Keeping aperture between f/11 and f/22 will give you a deep depth of field - the higher the f-number, the more of the flower will be in focus. Doubling the f-number will also double the depth of field. f/16 is the sweet spot as it gives you 50% more DoF than f/11, is not as soft as f/22 due to diffraction and still allows for shutter speeds about 1/100s at a low ISO.

With any lens you can always gain a bit of depth of field at the expense of magnification: just step back or zoom out a little so the framing is less tight.

Hi Dem.  Actually the tripod helps immensely as it did on this photograph.  If there is a slight breeze I will go to a faster shutter speed.  You should see what happens when I try hand holding the equipment.  Photo looks like a bowl of mashed potatoes.  :))  Yup, true story.  I really appreciate the information you offered regarding the f/stops for achieving maximum results for deep or shallow depth of field.  How do I get to Carnegie Hall?  Practice, Practice, Practice.  Thanks again.  Tony



#10
Tony

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All good suggestions above. However, when I look at that photo the first thing that pops into my head is that it needs a small amount of off camera flash.

 

Depth of field is definitely a problem but if you close down your aperture to gain depth of field, you open up another can of worms... namely camera shake or noise from bumping the iso to high in order to compensate. Use a speedlight and ta-da!  As an added bonus, flash serves to separate your subject from the background and brighten things up a bit. As it is, even with all that color, the image looks a bit flat and drab.

 

If you have a TTL flash, cool. Let it do it's thing. But even if you have a flash that only supports AUTO (on the flash) set it to that, set your camera to F/16 @ whatever your sync speed is and shoot. As long as you stay inside the AUTO range of the flash you should be good to go.

 

--Ron

Very interesting commentary.  For some reason I just cannot seem to get the brightness level correct.  Given the fact that my aging eyes will not tolerate so much brightness and being uncomfortable.  This is another good point to ponder and that is that you felt the image was flat and drab.  I thought it looked great with all the colors of red, pink,brown and white offering a nice assortment to view.  You see, my background is in Accounting and Taxes.  The saying goes that;  You can put 21 CPAs in a classroom, give them a tax problem to solve and guaranteed you will get 21 different solutions. I do have a Nikon SB-24 Speedlight which I like a lot and again you are correct that since it does have TTL and Auto, I should use it more and I will.  Well, as always your points are well made and will be utilized in the very near future.  Again, I am not really confident about what to do with the brightness levels.

 

Rgds,

 

Tony


I will post another photo taken with the same equipment.  You will see why I really like the AFNikkor 28~105mm D Lens.

 

Thanks for viewing.  EXIF:  Nikon D70, AFZoom Nikkor 28~105mm f/3.5~4.5D IF Lens.  SS 1/400s, F/8 @ 80mm.  Metering is Pattern.  tt

 

Antonio

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#11
Ron

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Maybe flat and drab were a bit harsh. What I was trying to imply is that the image... even with all the color, lacked 'pop'. Something to separate your subject from the background. You could do this post but it requires tools that allow you to work on discrete areas of the image (Lightroom and/or Photoshop/Photoshop Elements). 

 

You are correct in stating that how two persons perceive an image can (and often does) differ. I'm giving you my opinion. Others may not agree.

 

As an amusing aside to our discussion, I recently had to make prints of some of my award photos for use at a awards banquet. After I made a print of one image, I had the same thought ... gee, it's too flat. It looked great on the monitor but when it printed it out, it lacked the aforementioned 'pop'. I had to go back into Lightroom and correct the exposure a bit to compensate. So, as you see, it happens to all of us.... well, at least it happens to me.

 

--Ron



#12
Merco_61

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This lack of "pop" is the main reason I almost stopped using consumer normal zooms many years ago. There are situations where even the plastic nasty 35-80 is the right tool, but the lack of microcontrast makes for much work in post... The 28-105 is one of the better in it's class, but a 85/1.8H, AF-S 85/1.8 or an Ai 105/2.5 are better choices for most situations where you would want a short tele lens as they draw the border between sharp and unsharp better. The 90-105 mm macro segment, both Nikkors and third-party, are nice for flowers too, with the added advantage that you can come much closer.







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