Crop vs FF DOF


rocketatw

Senior Member
Jan 15, 2010
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#1
As we sometimes do not wish to use flash in low light, we only can depends on fast lens like Sigma 50mm F1.4

I am currently using Canon 7D and occasionally i will take photos of food in low light condition, i do not want to use flash and do not want to booast my ISO, so i use a F1.4, but i find it is not able to make the whole plate of dish to be in focus, of course i know i can set to F5.6 or F8 to make everything in focus, but that will be too slow and possible handshake. Hence, i am wondering will FF solve this problem assuming both camera are set to F1.4

Will FF see less part of my dish, or see more part of my dish.
 

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ctxx83

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Nov 29, 2010
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#2
yeah i experience this problem too. i wan the whole dish to look sharp but instead the focus is only on one part of the picture. if i adjust the F, the whole picture becomes dark.... What can we do? Thank you all for the advices in advance
 

spree86

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Feb 3, 2009
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#3
FF sensors will provide a shallower DOF, means that you will see less of your plate. The ways to solve this you alr said, eithier boost your ISO or use a flash.
 

rocketatw

Senior Member
Jan 15, 2010
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#4
FF sensors will provide a shallower DOF, means that you will see less of your plate. The ways to solve this you alr said, eithier boost your ISO or use a flash.
this is what i suspect too, can i say FF also have more blur background assuming all setting the same for Crop and FF?
 

Feb 27, 2008
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#5
50mm on a cropped 7D is a little too long for food at your own seat IMHO. Will it help if you shift the dish further away?
 

spree86

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Feb 3, 2009
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#7
this is what i suspect too, can i say FF also have more blur background assuming all setting the same for Crop and FF?
Yes, at the same f-stop, the image from a full frame will have more background blur than a that from a cropped body, since at the same focal length, the FOV is essentially different.
 

Nov 15, 2008
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#8
dun want to use high iso, dun want flash. Still want deep dof.........

Set to f8 and use a table top tripod lah....
 

Nov 15, 2008
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#9
Try to play around with your flash, better if your flash can zoom. The food will be in focus even at f1.4 when there is plenty of light.
dof and availability of light is 2 different item altogether.......

where got theory plenty of light = deep dof......
 

ZerocoolAstra

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Mar 13, 2008
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#10
kentwong81 said:
Try to play around with your flash, better if your flash can zoom. The food will be in focus even at f1.4 when there is plenty of light.
Your last sentence sounds confusing to me.
At f/1.4 and focusing close, dof should be pretty thin. Having more light would just make it overexposed. Having more light would allow you to stop down and achieve greater dof.
 

Rashkae

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Nov 28, 2005
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#11
Try to play around with your flash, better if your flash can zoom. The food will be in focus even at f1.4 when there is plenty of light.
I think you need to read up on the basics again.
 

Kiwira

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Aug 24, 2009
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#12
ff shallower dof

and further the distance between you and the food, you will get your entire food and the plate to appear sharper
 

Diavonex

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Sep 23, 2008
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#13
You'll probably solve your problem with a PNS with a small sensor (1/2.55"). That'll give you good DOF with aperture wide open.
 

kentwong81

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Jun 18, 2010
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#14
After reading TS question again, maybe my understanding is different with u guys here. I thought he is having focusing issue due to lack of light, which causes the camera gauge the wrong focal plane that makes the food not in focus.
Maybe TS should try a wide angle lens. A 24mm lens has four times the depth-of-field as a 50mm lens, you can get quite a lot in focus at f/1.4, while with a 50mm f/1.4, you barely get anything in focus at f/1.4. You can get a lot more sharp in your low-light hand-held images with a 24mm f/1.4 than even with a 50mm f/0.95.
 

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ZerocoolAstra

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#15
After reading TS question again, maybe my understanding is different with u guys here. I thought he is having focusing issue due to lack of light, which causes the camera gauge the wrong focal plane that makes the food not in focus.
Maybe TS should try a wide angle lens. A 24mm lens has four times the depth-of-field as a 50mm lens, you can get quite a lot in focus at f/1.4, while with a 50mm f/1.4, you barely get anything in focus at f/1.4. You can get a lot more sharp in your low-light hand-held images with a 24mm f/1.4 than even with a 50mm f/0.95.
ah ok I see where you're going. You're thinking along the lines of lack of light afffecting the ability to achieve accurate focus lock?

But TS did say quite explicitly in the 1st post that the main problem is not being able to get the whole dish/plate in focus. If stop down, the greater DOF can effectively cover the dish, but then the problem of hand-shake comes into play.
 

ZerocoolAstra

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#16
this is what i suspect too, can i say FF also have more blur background assuming all setting the same for Crop and FF?
Because of the FOV difference, if you want to achieve the same composition with FF as you got with a crop camera, you will either:
a) have to go closer (hence also focusing closer)
b) use a longer focal length (eg. 80mm instead of 50mm)

both of which will cause the DOF to be thinner, assuming you use the same aperture value.
 

rocketatw

Senior Member
Jan 15, 2010
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#17
what is fov by the way?

Let's say if I manage to get the same composition for crop using 50mm and ff using 80mm, both at same aperture, the ff will still see less part of the dish right?
 

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spree86

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Feb 3, 2009
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#18
what is fov by the way?

Let's say if I manage to get the same composition for crop using 50mm and ff using 80mm, both at same aperture, the ff will still see less part of the dish right?
FOV=field of view

If you use a longer focal length on FF to get the same picture as cropped frame then yes, you will see less part but if you take a picture at same focal length then crop out in your computer, then the DOF is the same
 

ZerocoolAstra

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#19
Just to follow on from spree86's post, putting in some numbers this time:

Scenario:
Canon 7D (1.6x multiplier) set up with 50mm f/1.4 lens. Focusing to 1.00m.
Depth of field = x

Canon 5D (FF) set up with 80 f/1.4 lens (imaginary... don't think there is such a lens). Focusing to 1.00m (same field of view as the 50 on 7D).
Depth of field = less than x

hope that clarifies things a wee bit :)
 

rocketatw

Senior Member
Jan 15, 2010
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#20
i think i got it, thanks to everyone here especially ZerocoolAstra and spree86.:thumbsup:
 

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