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08-06-2017, 11:28 AM - 4 Likes   #1
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Don't swear off your lens until you try this trick

A lot of people swear off their lenses stating that the lens is soft wide open. Actually it's their technique that might be lacking. Of course a lens is going to be a bit softer at f1.8 than at f8, but there shouldn't be that much of a variation, if you have a good lens. The problem is that at wide apertures the DOF becomes very shallow and the slightest little movement can throw your focus off. It's almost like shooting with a Super telephoto lens, if you sneeze the focus is off.

For shooting at wide apertures, unless you have nerves of steel, I would recommend using a tripod or a mono-pod. Especially if you are shooting indoors or in dim lighting situations. Even with a tripod the process of pressing down on the shutter with your finger can cause shake and blurry your picture. To avoid this you might try shooting with the mirror up, or using a shutter release, or the self-timer. That way your finger, does not get in the way. When using a monopod, I recommend placing the monopod in between your two legs that way it acts as a third leg(same as a tripod), then pressing down on the monopod slightly(towards the ground), hold your breath and gently press on the shutter button. Another thing that can cause blurry pictures or "not-as-sharp pictures" especially when shooting wide open is believe it or not, removing the camera from your face too quickly after you hit the shutter button. Not sure why, but if you keep the camera still for 1 or 2 seconds next to your face after you hit the shutter button, the pictures seem to come out sharper(well at least with me).


The way I test my lenses is not by some ridiculous charts and complicated graphs as do the pro reviewers(although I read these too) . I use a simple calendar hanging on my wall with large and very small lettering almost like the charts you use when you go see an eye-doctor. if you can find a calendar with shadow lettering the much better, because bad lenses have trouble making out the subtle shadows in the lettering. Then from about ten feet, I take a series of pictures from the lowest to the highest aperture. Sometimes I have to repeat this 2 or 3 times or more, to make sure it wasn't my technique that ruined the picture, or gave me a wrong impression. When satisfied, I compare these results under the same lighting and conditions with one of my better lenses.

Of course sharpness is not the only thing in a lens. There are other things like color rendition, micro contrast, character, pixel dust etc.. Unfortunately using a monopod or tripod is not always convenient or appropriate, but don't blame the lens if your pictures come out soft...


Last edited by hjoseph7; 08-06-2017 at 11:55 AM.
08-06-2017, 11:55 AM   #2
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Sometimes, DoF is so thin wide open that there isn't much of the subject in focus. We usually want the whole subject sharp with a soft background, and that is only possible by stopping down the lens and if there is enough separation between the subject and the background.
08-06-2017, 12:59 PM - 1 Like   #3
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QuoteOriginally posted by biz-engineer Quote
Sometimes, DoF is so thin wide open that there isn't much of the subject in focus. We usually want the whole subject sharp with a soft background, and that is only possible by stopping down the lens and if there is enough separation between the subject and the background.
My experience on this site is that many users don't realize how thin DOF is at even f/2.8 with moderate subject distance and normal viewing distance and how absolute thin it becomes when viewing that same image at full resolution (1:1 pixel mapping) on their computer monitor. This observation usually comes on threads where the complaint is made that the camera cannot consistently nail focus on eye glint in profile portraits. My advice is usually to stop down. As you noted, the proper way to get subject isolation is to choose an aperture where the full depth of the subject is in acceptable focus and the background is distant enough for adequate blurring.

Steve
08-06-2017, 01:14 PM - 1 Like   #4
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QuoteOriginally posted by hjoseph7 Quote
A lot of people swear off their lenses stating that the lens is soft wide open. Actually it's their technique that might be lacking.
Indeed! There is a reason why manual focus film cameras have focus aides and why so many owners of fast AF glass complain about performance. When a user on this site complains of focus issues or soft results, I generally suggest they step back a bit and allow the lens to show what its capable of without having to compete with camera/subject motion and/or poor focus technique.
  • Camera on tripod to avoid motion and position shift
  • Remote or self-timed release
  • Non-ambiguous subject (adequate detail and contrast to allow easiest focus)
  • Moderate distance. This is a big one since everything associated with distance works against both the lens and the photographer.
  • Manual focus using magnified live view
Once confidence in the lens is established with a controlled setup, one can more easily see how much technique counts.


Steve

(...was quite ready to throw my Jupiter-9 and my fast 50s away until I got a decent focus screen...)

08-06-2017, 01:29 PM   #5
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QuoteOriginally posted by stevebrot Quote
Indeed! There is a reason why manual focus film cameras have focus aides and why so many owners of fast AF glass complain about performance. When a user on this site complains of focus issues or soft results, I generally suggest they step back a bit and allow the lens to show what its capable of without having to compete with camera/subject motion and/or poor focus technique.
  • Camera on tripod to avoid motion and position shift
  • Remote or self-timed release
  • Non-ambiguous subject (adequate detail and contrast to allow easiest focus)
  • Moderate distance. This is a big one since everything associated with distance works against both the lens and the photographer.
  • Manual focus using magnified live view
Once confidence in the lens is established with a controlled setup, one can more easily see how much technique counts.


Steve

(...was quite ready to throw my Jupiter-9 and my fast 50s away until I got a decent focus screen...)
Most DoF charts show about 1/3 of the zone of focus is in front of the focus plane and 2/3 behind it. At wide alertures such as f/1.2 or f/1.4 on a 50mm lens, the focus zone at 8' distance can be as little as 4" inches - less than eyelash to back of hair. At a wide aperture it is often the area slightly behind the focus plane that appears out of focus, when in fact it merely isn't far enough behind the focus zone to be sufficiently blurred; other times User Error causes the critical focus plane to be slightly misplaced (as little as an inch!) with no room to forgive the error.

Last edited by monochrome; 08-06-2017 at 01:37 PM.
08-06-2017, 02:31 PM - 1 Like   #6
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Another myth is shooting at f16. A lot of experts discourage you to shoot past f8, because it will bring on diffraction. Those shutter speeds are not there for decoration folks, they are meant to be used and to increase your creativity. There is some truth that at higher apertures the contrast is not as good as let's say f5.6 or f8, but it does not mean that higher apertures will absolutely ruin your pictures. If you are not sure of this, then take a test at f8 then at f16 and try to see the difference. The differences should be slight. When I was shooting Large Format I used f32, f42 and higher with no problems. Sometimes you want every thing in the picture to come out sharp, from front to back. If your lens aIlows you to use f16 then why not use it ?

Last edited by hjoseph7; 08-06-2017 at 04:56 PM.
08-06-2017, 03:08 PM   #7
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As stevebrot brought up, distance is of great importance for DOF. Also, along with that is the degree of magnification, whether tele or by close-focus. If shooting say a skyline or cityscape at a great distance, the focus being at or very near infinity, DOF issues tend to become moot. But if a subject is within a generally moderate distance, DOF can become critical, especially when using a large aperture.

And shutter speed certainly can become a real issue, especially with live subjects, even though employing SR.
08-06-2017, 04:20 PM - 1 Like   #8
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QuoteOriginally posted by hjoseph7 Quote
Another myth is shooting at f16. A lot of experts discourage you to shoot past f8, because it will bring on diffraction. Those shutter speeds are not there for decoration folks, they are meant to be used and to increase your creativity. There is some truth that at smaller apertures the contrast is not as good as let's say f5.6 or f8, but it does not mean that higher apertures will absolutely ruin your pictures. If you are not sure of this, then take a test at f8 then at f16 and try to see the difference. The differences should be slight. When I was shooting Large Format I used f32, f42 and higher with no problems. Sometimes you want every thing in the picture to come out sharp, from front to back. If your lens aIlows you to use f16 then why not use it ?
This is especially true with a macro lens, where the lens is usually still plenty sharp despite diffraction, and where (for macro or close focus shots) you often want every bit of DOF you can extract.

The landscape photographers can weigh in here, but personally I don't see gains from stopping down a lens too much for a typical camera-to-horizon landscape. (I agree with @mikesbike ) For example, my experience with the DA 12-24 is that there is plenty of DOF at f8 or f11 (focusing about 1/3 of the way in to the scene), without needing to incur a diffraction hit by going further.

08-06-2017, 06:16 PM   #9
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QuoteOriginally posted by hjoseph7 Quote
The problem is that at wide apertures the DOF becomes very shallow... ...if you sneeze the focus is off.
The way I sneeze sometimes, I can be shooting at f2048 and the focus will be off...

More seriously, this topic raises questions about the need for the fastest lenses, given that often the dof wide open is shallower than the subject itself. This question can be applied to the argument that FF provides more DOF control than APS-C. Yes, it may, but is it actually needed?

Just thinking out loud...
08-07-2017, 05:10 AM   #10
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I have also found that almost every lens I own can benefit from some fine focus adjustment in the camera body. Wonder how many people take the time to dial their lenses in?
08-07-2017, 09:00 AM - 1 Like   #11
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A common mistake shooting landscapes with an UWA (14mm and wider on crop, and 21mm or wider on FF) is that the lens designs tend to have considerable field curvature. Even moderate wides, such as the Tamron 17-50, can have extreme field curvature at the wide end. So, shooting at no less than f/11 will yield the sharpest results more evenly, and f/16 is often optimal.

Another major concern, especially when shooting faster lenses, is focus shift. The Samyang 85mm f/1.4 shows considerable focus shift in the f/2-3.6 range, so critical work demands focusing with the lens stopped down. Past about f/4 the DoF pretty much eliminates the issue.

Understanding the limitations of a lens and the situation is a big part of the process of getting the best images.
08-07-2017, 09:23 AM   #12
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A tripod, MLU, cable release and a magnifier attached to the viewfinder, are your friend for any critical focusing.

Phil.
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