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depth of field focus question

richardg

richardg

Admonishtrator
For a small object, 3 inches by 3 inches, I am getting severe blur at the rear or the front of the object, depending on where I focus. The camera is about 12" away...am I right assuming that the further away from the object I go, the less it becomes an issue? Going back to 24" seems to have not helped at all.
 
Rich,

A smaller aperture, like f/11 or f/16, may solve your problem.

depth-of-field.jpg


For any point of focus, you have more depth of field behind than in front of the point of focus, so I'd suggest focusing about a third of the way on the object and using a small aperture like f/16.

Joe
 
Depth of field depends on aperture and distance, and to a lesser extent, the focal length of your lens. So, getting more light and choosing f16, or f22 if you have it, would help. What would also help is putting away your camera and using your phone. The tiny sensors in phone cameras give great depth of field, if you can persuade it to focus really close. My relatively modest Samsung A40 will focus down to about 4cm, and the depth of field is about 6cm as far as I can work out pointing it at a ruler on my desk. I don't think I could achieve that with any of my lenses.
 
I think for any given reproduction ratio, the focal length of the lens has no bearing on depth of field.

Or maybe I'm remembering wrong.

Joe
 
Joe P said:
I think for any given reproduction ratio, the focal length of the lens has no bearing on depth of field.
Or maybe I'm remembering wrong.
Joe
Click to expand...
No, I think you are entirely correct, but longer focal length lenses tend not to focus as close as wider lenses, so you sort of have to choose your lens based on working distance, and the closer you are, the bigger the problem!
 
Joe P said:
Rich,

A smaller aperture, like f/11 or f/16, may solve your problem.

depth-of-field.jpg


For any point of focus, you have more depth of field behind than in front of the point of focus, so I'd suggest focusing about a third of the way on the object and using a small aperture like f/16.

Joe
Click to expand...
thanks I will try it....will I lose colour? I got to this setting after many weeks of randomly changing stuff and the carbon always looks really black, there is a risk of it looking silvery grey..
 
JemHayward said:
Depth of field depends on aperture and distance, and to a lesser extent, the focal length of your lens. So, getting more light and choosing f16, or f22 if you have it, would help. What would also help is putting away your camera and using your phone. The tiny sensors in phone cameras give great depth of field, if you can persuade it to focus really close. My relatively modest Samsung A40 will focus down to about 4cm, and the depth of field is about 6cm as far as I can work out pointing it at a ruler on my desk. I don't think I could achieve that with any of my lenses.
Click to expand...
Thanks for that, I keep going back to phones, mainly for convenience. My daughter's just got an iphone 10 and I tiink it is possibly good enough, but I abandoned phone use with my iphone 5 5 years ago beause the auto-focus too often focussed on the wrong area of the product. Can you get them to manually focus now? I have not checked on my daughter's phone. The other thing is, my android phone would not do square photos, the iphone would.

Edit, I just checked her phone and I think there is no manual focus. I took a photo of my keyboard, it focussed on the front third but I want it to focus on the middle third so that the whole keyboard is pretty much in focus.
 
Rich,

If your lighting and exposure don't change, using a smaller aperture will not make the photo appear washed out.

Joe
 
Joe P said:
Rich,

A smaller aperture, like f/11 or f/16, may solve your problem.

depth-of-field.jpg


For any point of focus, you have more depth of field behind than in front of the point of focus, so I'd suggest focusing about a third of the way on the object and using a small aperture like f/16.

Joe
Click to expand...

This is very good advice...imho..
 
all above is good stuff. On studio shoots, flash is helpful if you have good lighting kit, since you can use very small apertures at a sensible, hand held shutter speed.
There is always more in focus beyond the precise focus point than there is in front. So focus about 1/4 or 1/3rd down your object, not on the front edge.
Move back a bit by using a longer lens. You don't need a fast aperture lens anyway.
Ideally, a standard 50mm, or a portrait lens like an 80mm work very well.
Use the camera on Aperture priority and set it at f11/16.
For a hand sized object, a working distance of 1meter or more should cure the problem unless the object is huge.

Snags.
Flash needs to be well placed and used in soft boxes to give it's best. Next best is natural light from a window, softened by a net curtain, with a reflector or 2 to fill any shadows.
Lenses tend to be at their sharpest stopped down 2 or 3 stops from wide aopen, so an f2 lens is sharpest around f4, after which they soften again, some quite dramatically. Luckily, this means a budget(ish) 80mm f4 works very nicely at f11.
 
richgilb said:
Lol...erm f5.6, whatever that means!
Click to expand...
The f-number is the lens focal length (50mm, 80mm, 135mm, etc) divided by the aperture size, ie the opening to let the light through. A 50mm f2 lens has a 25mm wide aperture when wide open. At f4 the aperture is 12.5mm, at f8 6.25mm dia, etc. Because of the way lenses work a fixed f-number lets a fixed amount of light through regardless of the lens focal length. This means that if you go from a wide angle lens it 28mm, f4 and say 1/125 of a second, changing to a short telescopic at 135mm, f4 will still give you 1/125 sec for the same exposure.

This is why long lenses don't go below about f5.6 or maybe even f8 unless you spend a hill of money. f2 is easy on a 50mm lens, 25mm dia gets you there. on a 200mm lens you need 100mm so the thing is already 4" across, and to get f2 at 500mm, which nobody offers, you would need an aperture 250mm wide, which is near enough 10" wide. To make this in optical quality would be eye-watering. That's why the sports guys you see at the side of football pitches and racecourses with lenses like dustbins have spent the price of a decent second hand car on glassware. 500mm at f4 needs an aperture 125mm across, which is bigger than a pint mug.
 
Derek Wright said:
hu la la etc

but this is your business selling items so make sure that you display them in the most atttractive way.
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Quite hard. No-one has really done a superb job in the industry. The products are typically large, glossy, curved and black motorbike mudguards. I can diffuse light until the whole room is used up but you can see so obviously what is going on in the reflections. I can move the product a million times but it just moves the reflections around.
 
The real answer to all this is to use a camera with movements, preferably front and back movements. You can then use the movements to change and control the plane of focus.

I suppose no one these days, unless they specialise and make their living in small product photography, are going to go to the expense of something like an Arca with a digital back, but when I had my Linhoff Technica MKIV film camera this sort of thing was well within its capabilities.
 
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