[PerrynBecky]

Hi everyone, I have been getting some pictures on photo stock sites that have been accepted, and it seems for every one accepted, 5 are rejected because of "focus issues".

I have a Nikon d3100, and I have a starter lens (18-55 mm), and a 55-300 mm lens. I have heard there is a formula you use to determine your ideal settings vs the distance, to bring a certain range in focus, but I find this rather confusing based on the info so far that I have read on it. I shoot in manual, and I can get some pretty pics that are real sharp, but not "magazine" quality. I use a tripod with a remote shutter when taking still shots, and I use the viewfinder only. Never live view.

Any tips or links on this subject would be greatly appreciated.

Perry

[vlad]

Could you post a few examples for us to debug?

[EnglishBob]

If your "missing" the focus, a tripod and shutter realease won't help, you need greater depth of field.

The smaller the aperture, the greater the depth of field. Try increasing the F-stop incrementally until you have the entire object in sharp focus. (higher number = smaller hole = greater depth of field). Now your problem will be lighting and exposure.

[jinko]

The depth of field will also depend on the objective, the focal length used in capturing an image and the distance of the subject from your camera. As a rule of thumb, if you want the whole scene in focus, you should use a small aperture and focus on the first quarter or third of the scene looking from your camera.

[PerrynBecky]

If your "missing" the focus, a tripod and shutter realease won't help, you need greater depth of field.

The smaller the aperture, the greater the depth of field. Try increasing the F-stop incrementally until you have the entire object in sharp focus. (higher number = smaller hole = greater depth of field). Now your problem will be lighting and exposure.

Thanks for the tip, English Bob. I definitely will have to try that.

Perry

[PerrynBecky]

The depth of field will also depend on the objective, the focal length used in capturing an image and the distance of the subject from your camera. As a rule of thumb, if you want the whole scene in focus, you should use a small aperture and focus on the first quarter or third of the scene looking from your camera.

Thanks for your help, Jinko.

Perry

[PerrynBecky]

Could you post a few examples for us to debug?

I tried to include a few with the original post, and it wouldn't accept the attachments for some reason. Not sure what's going on there. Is there a size restriction? Does it have to be a zipped file?

Perry

[EnglishBob]

jpg files are the normal attachment.

[vlad]

Try to post jpeg files resized to 1000 pixels on the long edge, using a compression level of 80. You can use just about an software to resize. Gimp, Photoshop, Lightroom, even IrfanView or the simple Fast Image Resizer.

[kNox]

I've got the same gear as you: D3100 with the stock 18-55 and a 55-300. What I found is that the D3100 sometimes has problems with auto focus - try taking more shots in the same angle and re-do the autofocus each time (maybe even change the focus point between shots), if you take a couple photos one or two are bound to be good.

[photokev]

Hi Perry,
There are 2 issues that could be going on here, lack of focus OR lack of sharpness. Make sure you're working on trying to fix the right one.

Sharpness...
Lack of sharpness is usually attributed to camera or subject movement during the exposure. Many of my students (most new photographers actually) go through a learning curve where they learn what can be hand held and what can't. Long lenses and low light are the enemies, shutter speed and ASA settings are your friend when you have to hand hold, tripod or a monopod is your best bet when you can use them. For moving subjects, learn and practice the techniques of panning with your subject or prefocusing at a spot on the ground that You know your subject will pass over.

Modern DSLR cameras have awesome light sensitivity and allow you to shoot in low light levels (at a high ASA) without picking up a lot of noise in the image. Try bumping up your ASA and shooting at a higher shutter speed to counteract camera shake. See if that helps the issue your having.

The other factor affecting image sharpness is lens quality. There's a reason pros use expensive glass, the image quality is much better. (among other things) I recommend to my students that are on budgets, that they purchase a cheaper camera body and spend most of their money on lenses.

Focus...
Two parts to the focus discussion, Focus and Depth of Field. Focus is a mandatory part of the image and DOF is a design element (with an exception for moving objects). Your subject or the part of your subject you want to emphasize must be tack sharp. In a portrait it's the eyes, in a head a shoulders shot you might want all the subject in focus. In these same examples DOF is used in conjunction with focus to control how your final shot will look. A shallow depth of field will enhance your subject by making it pop. A deep depth of field will keep everything in focus which may or may not be a good thing.

Focus is critical and the ability to do it well is somewhat controlled by the equipment you use. A nice bright viewfinder on your camera is necessary to help you see what's going on and in the case of an auto focus, what your camera is actually focusing on. A dark viewfinder or trying to use an lcd viewfinder on the back of a camera to determine sharp focus is a recipe for disaster.

Depth of Field...
Someone above listed the 3 main variables in depth of field:
Focal length of the lens (The longer the FL the shallower the DOF)
Distance to the subject (The closer you are the shallower the DOF)
Aperature (The smaller the aperture, the shallower the DOF)

A 4th variable is sensor size. Smaller sensor cameras tend to have a greater DOF (but less sharpness).

As I mentioned earlier, DOF should generally be used as a design element and not as a focus tool. What I'm trying to say is that you shouldn't be trying to shoot using setting that provide a large DOF with the hope that your subject will be in focus. Focus first and then control the DOF to give yourself the shot you want. Use the concept of pre-visualization. See the shot in your head and use the camera as the tool to make it happen.

Hope this helps!

[NT73]

Aperture (The smaller the aperture = a larger f. no. the greater the (DOF)
The wider the aperture (The smaller the DOF)

[photokev]

good catch NT, thanks!

[PerrynBecky]

Hi Perry,
There are 2 issues that could be going on here, lack of focus OR lack of sharpness. Make sure you're working on trying to fix the right one.

Sharpness...
Lack of sharpness is usually attributed to camera or subject movement during the exposure. Many of my students (most new photographers actually) go through a learning curve where they learn what can be hand held and what can't. Long lenses and low light are the enemies, shutter speed and ASA settings are your friend when you have to hand hold, tripod or a monopod is your best bet when you can use them. For moving subjects, learn and practice the techniques of panning with your subject or prefocusing at a spot on the ground that You know your subject will pass over.

Modern DSLR cameras have awesome light sensitivity and allow you to shoot in low light levels (at a high ASA) without picking up a lot of noise in the image. Try bumping up your ASA and shooting at a higher shutter speed to counteract camera shake. See if that helps the issue your having.

The other factor affecting image sharpness is lens quality. There's a reason pros use expensive glass, the image quality is much better. (among other things) I recommend to my students that are on budgets, that they purchase a cheaper camera body and spend most of their money on lenses.

Focus...
Two parts to the focus discussion, Focus and Depth of Field. Focus is a mandatory part of the image and DOF is a design element (with an exception for moving objects). Your subject or the part of your subject you want to emphasize must be tack sharp. In a portrait it's the eyes, in a head a shoulders shot you might want all the subject in focus. In these same examples DOF is used in conjunction with focus to control how your final shot will look. A shallow depth of field will enhance your subject by making it pop. A deep depth of field will keep everything in focus which may or may not be a good thing.

Focus is critical and the ability to do it well is somewhat controlled by the equipment you use. A nice bright viewfinder on your camera is necessary to help you see what's going on and in the case of an auto focus, what your camera is actually focusing on. A dark viewfinder or trying to use an lcd viewfinder on the back of a camera to determine sharp focus is a recipe for disaster.

Depth of Field...
Someone above listed the 3 main variables in depth of field:
Focal length of the lens (The longer the FL the shallower the DOF)
Distance to the subject (The closer you are the shallower the DOF)
Aperature (The smaller the aperture, the shallower the DOF)

A 4th variable is sensor size. Smaller sensor cameras tend to have a greater DOF (but less sharpness).

As I mentioned earlier, DOF should generally be used as a design element and not as a focus tool. What I'm trying to say is that you shouldn't be trying to shoot using setting that provide a large DOF with the hope that your subject will be in focus. Focus first and then control the DOF to give yourself the shot you want. Use the concept of pre-visualization. See the shot in your head and use the camera as the tool to make it happen.

Hope this helps!

Thanks, this is a lot to digest, and I will have to go over it a few times to get it all to sink in, but it's vital info. Thank you again.

Perry

[DanDickens2]

The relationship to exposure control, being controlled by shutter speed and aperture settings - while living in the "Hand Held World" years ago I learned a simple formula at a Nikon show. In the Hand Held World depth of field may have to be the element sacrificed - sometimes. Here is formula for Hand Held work - (1) What is the lens being used? 50mm - then make sure your shutter speed is at 1/60th - or higher adjust the aperture accordingly. Thus - are you using an 80mm lens - then set your shutter speed to 1/100th or higher. 200mm lens - then 1/250th or higher. So whatever the mm of the lens - sellect a shutter speed nearest that number, on the high end or higher, and give up the depth of field with an aperture that maintains exposure control. Now with that said - If you have some great post processing or post production software such as Photoshop or onOne Perfect Photo Suite 7 - you can work in a lower exposure value giving you some greater depth of field by using a tighter aperture setting - and in post production fix the exposure issues - however, remember to maintain shaddow detail - best not go but two f/stops below the metered exposure value - if shaddow detail is not important - take it three or four f/stops below the proper exposure value. Works for me - give it a try - it should work for you as well. NOW as for Stock Houses - they are picky and may not accept post production fixes - not sure why - 99% of the public would not know the difference. But Stock suppliers have some realy high end detection software and they can spot a post production fix a mile away - plus they are looking for that rare image - to common topic that is not in their supply - picky, picky, picky - I want to start a Stock Site that takes anything out there - cause often I have been looking for a really bad image and can not find what I want from the stock suppliers - their stuff is so slick - but I have had some needs for some bad amature looks in some of our Ad Layouts - and I have to shot it myself.