Rule of thumb...how to get the best sharpness?

[Schizophonic]

I remember reading on another thread here how to get the correct shutter speed so that blur is to a min. With my 350D Im still on AV mode, not touching manuel mode, but I feel that I need more deapth to some of the photos.

What was that rule of thumb again?

 

[xolotl]

1:1 with the focal length. So if you are shooting at 50mm you want a shutter speed of 1/50

 

[Jotun]

Don't forget that with the 350d there is the 1.6x crop factor, eg 50mm will effectively be 50 x 1.6 = 80mm so if the lens is at 50mm, you will need to shoot at 1/80th of a second or faster.

 

[SDK^]

Don't forget that with the 350d there is the 1.6x crop factor, eg 50mm will effectively be 50 x 1.6 = 80mm so if the lens is at 50mm, you will need to shoot at 1/80th of a second or faster.

This always comes up and it's not necessary to match shutter with a crop factor camera.

 

[Jotun]

This always comes up and it's not necessary to match shutter with a crop factor camera.

Is there a reason for that? I always thought it made sense that it would be the case, and had just assumed it was.

Also would the same be true say if a 1.4x or 2x teleconvertor was used?

 

[Schizophonic]

1:1 with the focal length. So if you are shooting at 50mm you want a shutter speed of 1/50

Its easy to tell the focal length on a fixed lenth such as a 50mm but with the stock lens 18-55mm, is there a digital reader on the camera or do i have to just read the figures on the top of the lens?

 

[Mint_Sauce]

Best just to guess, if you're using the wide end and you're not fully wide then you can probably estimate a good enough guess. It's not set in stone anyway, it's just a rough guide. All kinds of factors will affect it like how steady your hands are to if it's windy to if you're on a rollercoaster. You know, that kind of thing.

 

[rpstewart]

Is there a reason for that? I always thought it made sense that it would be the case, and had just assumed it was.

The focal length doesn't change, it's just a crop out of the centre of the image circle. If, for example, you shot 1/50s at 50mm on a full frame camera and it was sharp then it's still sharp when you crop out the centre portion - this is all that happens in a 1.6x body.

Also would the same be true say if a 1.4x or 2x teleconvertor was used?

A TC actually changes the focal length so you would need to take this into account.

Its easy to tell the focal length on a fixed lenth such as a 50mm but with the stock lens 18-55mm, is there a digital reader on the camera or do i have to just read the figures on the top of the lens?

The camera does know the exact focal length and records it in the EXIF data, it isn't however displayed. You need to read the markings on the lens.

 

[Jotun]

The focal length doesn't change, it's just a crop out of the centre of the image circle. If, for example, you shot 1/50s at 50mm on a full frame camera and it was sharp then it's still sharp when you crop out the centre portion - this is all that happens in a 1.6x body.

Ah it seems so obvious now that you put it that way, cheers

 

[ChroniC]

Personally i would have said half the f-stop number/double the time, and visa versa.

If your in a low light situation but you want the less chance of blurring then you need more light over the ccd/film if you have no tripod then to stop blur you need a smaller aperture (i.e f22), at the sacrafice of not being able to achieve low depth of field.

So thus, if a correct exposure of f11 at 1/30 of a second (i.e going to blur) You need to go 2 maybe 3 stops up, to make exposure timing 1/250

I fail to see how focal length has anything to do with blurring, unless your talking about Hyperfocal distance which is a matter of depth of field not compensating exposure to stop blur?

1:1 with the focal length. So if you are shooting at 50mm you want a shutter speed of 1/50

Are you suggesting that they apply a f-stop that closest allows a shutter speed of 1/50 at 50mm? Wow im lost.

 

[SDK^]

If your in a low light situation but you want the less chance of blurring then you need more light over the ccd/film if you have no tripod then to stop blur you need a smaller aperture (i.e f22).

F22 is a narrow aperture and lets in less light.

Remember
High Aperture number (F22) = less light
Low Aperture number (F2.8) = more light

I fail to see how focal length has anything to do with blurring, unless

As you increase focal length you increase shake from holding the camera.
So, when using a long focal length (i.e. 300mm) you need to use a faster shutter speed (1/320) to ensure a sharp photo. Image stabilization (IS) is fitted to some lenses which roughly gives you 3 stops below focal length/shutter speed hand hold ability.

 

[hoodmeister]

my compact camera has a 4mm-7mm lens.
I cannot, despite my best efforts, get an even vaguely shake free shot from it @ 4mm & 1/4 second.

The 1/focal length rule was designed for the 35mm frame, but is one that pretty much guarantees a sharp shot even if you're fairly shaky. Which is nice when you can't check to see how sharp that shot is straight away.
With a crop body you do need better handholding technique to get a "sharp" shot at the same focal length and same shutter speed. But it's still well within the realms of do-ability for most, and many can even comfortably hold at much slower speeeds.

It's a rule of thumb, that's all, and a good starting point. As you get to know your abilities & equipment stability etc. you'll find that you can rely on it less and less.

 

[SDK^]

my compact camera has a 4mm-7mm lens.
I cannot, despite my best efforts, get an even vaguely shake free shot from it @ 4mm & 1/4 second.

You need to find the 35mm equivalent of your lens - what camera do you have ?

With a crop body you do need better handholding technique to get a "sharp" shot at the same focal length and same shutter speed.

No you don't - read rpstewart's post above

 

[hoodmeister]

No, the lens is 4-7mm
Sure, if I were to go by the 35mm equivalent of (roughly) 30mm - 80mm then I'd be laughing, but by your rationale I don't need to take into consideration the crop factor.

I was using that as an extreme example of how the rule is, to a greater or lesser extent, effected by the crop factor.

 

[xolotl]

Are you suggesting that they apply a f-stop that closest allows a shutter speed of 1/50 at 50mm? Wow im lost.

What I was suggesting, that on a 35mm frame camera with a 50mm lens you would need a shutter speed of 1/50 or above to make sure that shake does not effect image quality.

 

[ChroniC]

F22 is a narrow aperture and lets in less light.

Remember
High Aperture number (F22) = less light
Low Aperture number (F2.8) = more light

Sorry i so offen do that, just change the fstop number, it makes sense then ive been doing this for years and i still do that.

As you increase focal length you increase shake from holding the camera.
So, when using a long focal length (i.e. 300mm) you need to use a faster shutter speed (1/320) to ensure a sharp photo. Image stabilization (IS) is fitted to some lenses which roughly gives you 3 stops below focal length/shutter speed hand hold ability.

Ok, i didnt know that, i dont use zoom lenses that offen, as i dont find them necessary for studio work. Learn something every day.
However i wouldnt use that as a rule, ever. What the op wanted was to understand exposure timing, and blur. I suppose both rules should be understood.

What I was suggesting, that on a 35mm frame camera with a 50mm lens you would need a shutter speed of 1/50 or above to make sure that shake does not effect image quality.

i was always told 1/60th but i was never told why. Suppose that the next best thing, and makes sense.

 

[SDK^]

No, the lens is 4-7mm
Sure, if I were to go by the 35mm equivalent of (roughly) 30mm - 80mm then I'd be laughing, but by your rationale I don't need to take into consideration the crop factor.

Forget crop factor, sensor and indicated lens size - the focal length to shutter rule always refers to the 35mm lens equivalent regardless.

Canon 20D, 50mm – 1/50
Canon 1Ds, 50mm – 1/50
Canon G7, 8mm (50mm equiv) – 1/50

Yada, yada…

 

[hoodmeister]

Yes yes, I could repeat myself all day long, too.

For whatever reasons you're clearly dead set on your fact that this rule isn't effected by crop factor. There's no point discussing it with you.

Edit :
I didn't read your post properly, actually.. If you're adjusting the rule for the G7, why not the 20D?

 

[SDK^]

Edit :
I didn't read your post properly, actually.. If you're adjusting the rule for the G7, why not the 20D?

Because the 20D, 350D etc use 35mm lenses
Canon EF-S lenses are converted to 35mm so a 10-22 becomes 16-35mm

 

[SDK^]

There's no point discussing it with you.

I'm only trying to help you understand

Take a step back