getting accustom to FX..DOF - a double edge sword.


lunas

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#1
After using D800 for 3 wks, the shallow DOF of FX can post a problem if I take group pictures or having subjects that are meters apart.

In DX, taking into.consideration of the crop factor....I can get deeper DOF with F5.6; but for FX I need f8. Henceforth, I need to boost ISO AND flash output. As a result, I could get grainier photos and increase battery consumption on my flash.

How do u guys manage this?

Thank you.
 

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yrh0413

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#2
isn't higher ISO on your D800 still performs better than low ISO on your DX body? Say you may be limited to ISO800 on DX but you can shoot up to ISO6400 on FX yet your photos are cleaner than ISO800 on DX.
 

Ansel

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#3
After using D800 for 3 wks, the shallow DOF of FX can post a problem if I take group pictures or having subjects that are meters apart.

In DX, taking into.consideration of the crop factor....I can get deeper DOF with F5.6; but for FX I need f8. Henceforth, I need to boost ISO AND flash output. As a result, I could get grainier photos and increase battery consumption on my flash.

How do u guys manage this?

Thank you.
How do people manage? You already know. Use smaller aperture and boost ISO or slow down shuttle speed. This is not a new problem. During the film days, when people moved from 35mm to medium format had to deal with the same issues. It's physics, you can't run away from it. They key is to learn the strengths and weaknesses of each format and use them to your advantage.
 

lunas

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#5
How do people manage? You already know. Use smaller aperture and boost ISO or slow down shuttle speed. This is not a new problem. During the film days, when people moved from 35mm to medium format had to deal with the same issues. It's physics, you can't run away from it. They key is to learn the strengths and weaknesses of each format and use them to your advantage.
Well said, Bro. Thumbs up for you ;)

if you need deeper DOF use a DX/CX camera
right tool for the job
Yup. Now I TRULY know why DX is still here to stay :)
 

ortega

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#6
Well said, Bro. Thumbs up for you ;)

Yup. Now I TRULY know why DX is still here to stay :)
what if you just switched your d800 to DX mode?
when the camera to subject distance increases, your DOF will increase too

i will try
 

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san2001

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#7
DoF is related to focal length, not the size of the sensor.

At the same focal length and same aperture, EVERY camera has the same DoF, regardless of sensor size.
At the same Field of View and same aperture, the larger the sensor, the shallower the DoF. This is because to get the same FoV as say, a 35mm lens on a DX sensor, an FX user has to use a 50mm, which is longer.


There's no such thing as FX DoF. If you find that the DoF shallow for a particular focal length, use a wider lens and then crop later if necessary.
 

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Dav-C

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#8
For the same framing or FOV, if distance to subject is same, the FX uses a longer lens hence narrower DOF.

For the same framing or FOV, if use the same lens the FX got to move closer to subject which also results in narrower DOF.

To keep ISO low. If I am shooting 24mm, I would set ISO200, desired Aperture (say f/4 or f/8) and Shutter speed (1/30, or faster if the subjects like to move). Let TTL work. If too dark I would increase ISO gradually firstly I would want to ensure subjects are exposed properly, if possible I would increase the ISO until I can see the background as well (as I increase the ISO the TTL will gradually decrease its power). I would never set to ISO Auto, TTL and P/A/S mode together because it would be very hard to control and predict what the system does. If lighting extremely bright or dark I usually don't use TTL-BL. For TTL to work properly the subject better be in the middle, or you can use FV Lock function then recompose. Of course we are talking about general photography.
 

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daredevil123

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#9
You really have to know DoF well with the focal length used, and know how to place your subjects, position yourself as well as composition.

Don't worry, it is doable!
 

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sf_kang

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#11
Dav-C said:
For the same framing or FOV, if distance to subject is same, the FX uses a longer lens hence narrower DOF.

For the same framing or FOV, if use the same lens the FX got to move closer to subject which also results in narrower DOF.

To keep ISO low. If I am shooting 24mm, I would set ISO200, desired Aperture (say f/4 or f/8) and Shutter speed (1/30, or faster if the subjects like to move). Let TTL work. If too dark I would increase ISO gradually firstly I would want to ensure subjects are exposed properly, if possible I would increase the ISO until I can see the background as well (as I increase the ISO the TTL will gradually decrease its power). I would never set to ISO Auto, TTL and P/A/S mode together because it would be very hard to control and predict what the system does. If lighting extremely bright or dark I usually don't use TTL-BL. For TTL to work properly the subject better be in the middle, or you can use FV Lock function then recompose. Of course we are talking about general photography.
Hi Dav-C, Thks for sharing. Well explained. Regarding ISO Auto with TTL and P/A/S and flash photography, I also use the same approach as you do, i.e. never combine ISO Auto with TTL and P/A/S due to unpredictability of result. On ISO Auto, I use manual aperture n shutter.

Thks for sharing your experience about DOF and flash photography. Cheers. Fred
 

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#12
Not sure if anyone mentioned this.

The easy solution to this problem is to use a wide focal length. You will have a larger DOF using 24mm at f5.6 vs 50mm at f5.6, plus you don't have to stand that far away.
 

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san2001

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#13
Not sure if anyone mentioned this.

The easy solution to this problem is to use a wide focal length. You will have a larger DOF using 24mm at f5.6 vs 50mm at f5.6, plus you don't have to stand that far away.
I actually did, several posts above. Sometimes the most complex sounding problems have the simplest solutions.
 

daredevil123

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#14
Not sure if anyone mentioned this.

The easy solution to this problem is to use a wide focal length. You will have a larger DOF using 24mm at f5.6 vs 50mm at f5.6, plus you don't have to stand that far away.
problem is how wide can you go sometimes? especially when distortion starts coming into play... In the end, it is a balance. Which is why the photographer is the most important element. Knowing how to compose, using what focal length, to get the best result...

Photo shot at 50mm @ F1.4 on FF. Like I said, it is doable.

 

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sjackal

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Jul 9, 2008
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#15
After using D800 for 3 wks, the shallow DOF of FX can post a problem if I take group pictures or having subjects that are meters apart.

In DX, taking into.consideration of the crop factor....I can get deeper DOF with F5.6; but for FX I need f8. Henceforth, I need to boost ISO AND flash output. As a result, I could get grainier photos and increase battery consumption on my flash.

How do u guys manage this?

Thank you.
It is never a problem. Either you up the flash one stop or up the ISO one stop.
 

san2001

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#16
problem is how wide can you go sometimes? especially when distortion starts coming into play..
As the OP only needs to match his DX FoV, he doesn't need to go much wider. Only 1.5x times. And even though you're going wider, you don't place the subjects at the edges, you place them in the center within the DX FoV. The "wasted" areas can and should be cropped off later.

In this instance, we are going wide only for DoF equivalence, not for compositional changes.
 

daredevil123

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#17
As the OP only needs to match his DX FoV, he doesn't need to go much wider. Only 1.5x times. And even though you're going wider, you don't place the subjects at the edges, you place them in the center within the DX FoV. The "wasted" areas can and should be cropped off later.

In this instance, we are going wide only for DoF equivalence, not for compositional changes.
1.5 times is a lot wider. the best way is still to increase camera to subject distance.

and the moment you go wider, your composition changes, simply because the perspective is very different.
 

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san2001

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#19
and the moment you go wider, your composition changes, simply because the perspective is very different.
I don't think you got what I am saying.

Consider this image to be shot from a certain camera position, with a DX camera and a 50 mm lens.



Now to get the same FoV with an FX camera, you have to shoot with 75mm which of course means, less DoF at any given aperture.

Instead, shoot the FX camera with the same 50mm lens from the exact same position. You'll get something like this, with the same DoF as the DX shot.



If you now crop this down to match the DX shot, the perspective would EXACTLY be the same in terms of distortion. Go ahead and try it. It works for any FoV pairs in terms of equivalence.
 

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daredevil123

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#20
I don't think you got what I am saying.

Consider this image to be shot from a certain camera position, with a DX camera and a 50 mm lens.


Now to get the same FoV with an FX camera, you have to shoot with 75mm which of course means, less DoF at any given aperture.

Instead, shoot the FX camera with the same 50mm lens from the exact same position. You'll get something like this, with the same DoF as the DX shot.


If you now crop this down to match the DX shot, the perspective would EXACTLY be the same in terms of distortion. Go ahead and try it. It works for any FoV pairs in terms of equivalence.
If you do that for every portrait you take, why buy FX? Just buy a DX and save some money.

And what you just said is not "going wider" like you just said in a previous post. It is staying at the same focal length. Go wider, means using a wider focal length... And that is the premise of my first comment in reply to DemonicAngelz who was clearly talking about focal length... (see here). Apples and oranges dude.

And TS is not talking about DX vs FX.. TS is saying he has a problem getting enough DoF in FX...

BTW, you example has nothing to do with focal length... it is subject distance. Same lens, subject distance stayed equal = DOF stayed more or less equal... but do know, it is not exactly the same. There are still slight differences in DoF due to the different CoC between a DX and FX cam.
 

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