Need deep DOF with high zoom and close subject

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dance621

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james
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OK, new to the forum. But need some technical advise.

I need to zoom into a close subject (about 1 -2 meters away). ideally with a 300+mm focal length. But i need a deep depth of field (the back and the front of the model both in focus). 15cm depth of field would be ideal. Would digital compacts be better at this then SLRs due to their small sensors? If I am not mistaken smaller sensors mean greater depth of field? actually i want to take many images of the same model and then merge them into one super detailed image. She will be sitting very still. I have tried this with canon 400d with a tamron zoom set to 250mm, studio lighting, f14 but depth of field was very shallow. I could move closer with a smaller focal length. does that help? or is the smaller focal length offset by the shorter distance to the object?

Now I am thinking of trying with a canon compact superzoom. Maybe a powershot sx210. are all compacts built with the same size sensor?

The end product will be a close up of the model by stitching maybe 20 pics together. 150 megapixels if i am lucky. thanks
 
I could move closer with a smaller focal length. does that help? or is the smaller focal length offset by the shorter distance to the object?
Click to expand...

There's an easy way to find out ;)

150mp? what do you plan on using it for?
 
Even with a FF camera using a 300mm lens at 6' f32 gives just over 2" dof!

A wider lens will help but moving closer won't. Better to stand back then crop your image to suit.

50mm lens at 5' f8 gives 17" dof.

You may need to rethink strategy.
http://www.dofmaster.com/dofjs.html
 
You could try focus stacking if your subject is still enough.
 
Thanks for the replies. I am still not sure if a compact camera with a small sensor would give better depth of field. The purpose of the exercise is purely a technical one. I want to see if a very high megapixel stitched image can be used to print very large images. So standing back and then cropping in wont help. The stacking method. is there some freeware for that. And I wonder if sta,ked images can still be stitched. Doent the perspective change slightly when you change focus
 
dance621 said:
Thanks for the replies. I am still not sure if a compact camera with a small sensor would give better depth of field. The purpose of the exercise is purely a technical one. I want to see if a very high megapixel stitched image can be used to print very large images. So standing back and then cropping in wont help. The stacking method. is there some freeware for that. And I wonder if sta,ked images can still be stitched. Doent the perspective change slightly when you change focus
Click to expand...

Perspective does not change when changing only the focus.

At 6' and 200mm f16 even a compact only has 0.5" dof....

At 10' it's only 1.37"!
 
EOS_JD said:
Perspective does not change when changing only the focus.

At 6' and 200mm f16 even a compact only has 0.5" dof....

At 10' it's only 1.37"!
Click to expand...

Perspective can change on focus depending on the lens.

Cropped sensor will give greater depth of field everything else being equal.

If you focus stack several images you should still be able to stich, but obviously you're going to have to make sure nothing moves!
 
Interested to know how focus changes perspective (or are you talking about a tilt & shift which is not really appropriate to this discussion).
 
Alan Clogwyn said:
Perspective can change on focus depending on the lens.
Click to expand...

The only thing that changes perspective is the distance from subject to focal plane - focus or choice of lens has no effect.
 
awp said:
The only thing that changes perspective is the distance from subject to focal plane - focus or choice of lens has no effect.
Click to expand...

:thumbs: one word - Magnification.
 
Thanks again for the replies. I just wanted to post a link where I would the information that smaller sensors give deeper depth of field

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

I guess the maths is going to be a little intense for me but was wondering if it is worth getting hold of a camera. presumable the worse lens will lead to higher grain but this would be offset by the deeper depth of field.

As for the perspective changing with different focus, maybe i didnt mean perspective. It is just that is you have to stitch two photos together it might not work if different areas have different focus.
 
EOS_JD said:
Did you miss the link I posted.

http://www.dofmaster.com/dofjs.html
Click to expand...

I had a look at that but became even more confused. If you compare a 400d dslr with a canon a powershot a720 with equivalent focal length and f-stop the calculation shows that the 400d has a deeper depth of field. However, the link i posted suggests that compacts with smaller sensors have greater dop. who is right?
 
EOS_JD said:
Interested to know how focus changes perspective (or are you talking about a tilt & shift which is not really appropriate to this discussion).
Click to expand...

Why not?

I can use a Hasselblad 250mm or 350mm (if I had one) on my Mirex T/S adapter. with an extension tube will give the required focus and using the tilt as swing could bring the required plane into focus.
 
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