Newbe question on focal lenth: Hi there. Aldthough I'm a new poster I've been following this forum for some time. I am from Israel living in a Kibutz in the Arava desert. Im retired...

sebastian Loc: israel

Hi there. Aldthough I'm a new poster I've been following this forum for some time. I am from Israel living in a Kibutz in the Arava desert. Im retired and I've taken photografy as a hobby.
My question is parteining to the proper use of the 18/135 lens with the Sony A6100 camera. I'm aware of the "rule" that says that you shouldnt use a focal lenth minor to that of the lens for getting sharp pictures, but it is true too when shuting at 18 MM.?
I don't know if I expresed myself correctly because Englis is not my mother tongue, and I apologize for any unintended mangling that English has sufered.
I do hope that my question makes sense to someone and apologize for this longish post.
Thankyou un advance.
sebastian

maxlieberman Loc: 19027

Shalom. Generally, the rule of thumb is that your shutter speed should be no slower than the reciprocal of your focal length. So if you are shooting at 18mm, your shutter speed should be 1/20 of a second or faster. If your camera is a crop sensor, then you have to use the effective focal length, not the actual. If your lens has optical stabilization or your camera body ha IBIS, then you can go a couple of stops slower.

larryepage Loc: North Texas area

sebastian wrote:

Hi there. Aldthough I'm a new poster I've been fol... (show quote)

Sebastian...I think I understand what you are intending to ask. If my answer is not to the question you intended to ask, please let me know, and we will figure it out.

A general rule for a long time has been to use a shutter speed no longer than 1 divided by the focal length of your lens. For a 50mm lens, the slowest shutter speed would be 1/50 second. This is a general rule, and is considered valid for all focal lengths.

Of course, some people can hold a camera more steadily than others, so some may meed to choose a faster speed, and some may be able to use longer exposures. And now that lenses and some camera bodies have image stabilization, it is very often to use longer exposures with equipment having that capability.

One caution...this is a general guideline, not a hard and fast rule. Some may try to complicate it in all sorts of ways, including your sensor size and all sorts of things. Ignore all that. It is a simple guideline based on the physical relationship between the lens and the sensor.

Enjoy shooting, and please stay safe.

Flickwet Loc: NEOhio

1/apparent focal length, such as before IBIS or Lens stabilization, for instance, at 18mm on APS-C apparent “27mm” focal length your minimum recommended, hand held, non stabilized shutter speed would be 1/27th, now since there is unlikely a 1/27th sec speed attributable, go to the nearest available, taking into consideration your shutter speed as relates to the compromises of exposure. Another example is 140mm, 1/140mm(1.5)=280 thus 1/280th of a second.
On a stabilized system with IBIS or VR lenses you can use shutter speeds 2-7 (depends on age and type) stops slower, if you so desired.
However stabilization systems can’t freeze motion, that is only improved by increasing shutter speeds.
Also keep in mind “Apparent focal length”, just really “field of view”, crop sensors are just that, relative to full-frame 35mm (film)

Jimmy T Loc: Virginia

sebastian wrote:

Hi there. Aldthough I'm a new poster I've been fol... (show quote)

Your English is good and you are welcome here on the Ugly Hedge Hog!!!
Smile,
JimmyT Sends

Flickwet Loc: NEOhio

These from film daze… anyone else?
1/@f = shutter speed
1/asa @ f16 (sunny) “sunny sixteen rule”
a(a)+b(b) = c(c) is how we arrive at 50mm for a “ normal” field of view on a 35mm film or full frame sensor. I don’t know how to type it out on my phone correctly.
The square root of 2 is 1.4, a fast (widest opening) apeture, relativly easy to be construct based on Planar (there are others, but I’ll use Planar here) and Post Planar symmetrical lens designs.
So…f1.4,2, 2.8, 4, 5.6, 8, 11.2 (11 is fine), 16, 22… is how you calculate the aperture reduction by 2.

Orphoto Loc: Oregon

Congratulations on taking up a wonderful hobby in your retirement. The above advice is the usual suggestions. It assumes that you have steady hands. Stabilizations help if you dont. If you do get blurry images from too much camera movement then adjust to faster (briefer) shutter speeds. If you dont have enough light to make those adjustments consider leaning against stable strucures or using a tripod.

And yes, you can get away with using 18mm (wide) when longer is causing troubles. The limitations suggested above are more forgiving at 18mm than at 135mm.

sebastian Loc: israel

Thank you all. That was fast!
Got everything, but to simplify my queswtion, being a zoom? lens, shal I use it relating always as a 135 MM. regardless of the focal lens I'm using?
Is my understanding that the "rule" is because of the weight and lenth of the lens and shaking...
Thanks again
sebastian

maxlieberman Loc: 19027

sebastian wrote:

Thank you all. That was fast!
Got everything, but to simplify my queswtion, being a zoom? lens, shal I use it relating always as a 135 MM. regardless of the focal lens I'm using?
Is my understanding that the "rule" is because of the weight and lenth of the lens and shaking...
Thanks again
sebastian

Use the focal length that the lens is set at for the basis of your calculation. It has to do with the the camera Shake being nullified by the shutter speed, so it is a function of the focal length.

Flickwet Loc: NEOhio

I believe that 18-140 has VR, don’t worry about it too much, I believe in another famous statement: f8 and be there…

BurghByrd Loc: Pittsburgh

sebastian wrote:

Hi there. Aldthough I'm a new poster I've been fol... (show quote)

I have read the other replies and I believe as most did that the question is what shutter speed to use based on set focal length. Note I said SET focual length. This rule of thumb applies to unsupported hand held shooting. If you are on a tripod you can shoot as slow as desired and if supported (against a lamp post for example) you can also shoot much slower. For hand held if the SET focual length is at 18mm you can shoot at 1/18th second with reasonable confidence of producing acceptably sharp pictures if your technique is good. And at 135mm at 1/135s approximately and so on. Try looking through the camera with image stabilization off and vary the zoom from wide to telephoto; you'll notice that the image bounces around more at a telephoto (zoomed) length. A higher shutter speed is required to prevent this from producing blur.

I hope this answers the question.

Retired CPO Loc: Travel full time in an RV

This is all pretty good advice. Just be aware that these shutter speeds mentioned are for compensating for CAMERA movement as it affects sharpness. And lens/camera stabilization helps tremendously with that. Especially when using longer (telephoto) lenses.
Someone touched briefly on the other consideration. SUBJECT motion. It doesn't matter how firmly the camera is held if fast SUBJECT motion causes a blurred photograph. Panning with the action/motion and an appropriate shutter speed is the key to sharp photographs when SUBJECT motion is of concern!
Welcome to the HOG. I'm looking forward to seeing some of your photographs!

R.G. Loc: Scotland

sebastian wrote:

.... it is true too when shuting at 18 MM.?...

The more zoom you're using the faster the shutter speed that you need. And just as cropping in post processing has the effect of zooming in, so does using a crop sensor camera.

Some say that you should use a shutter speed that's twice as fast as the inverse of the focal length. For a full frame camera that's probably being over-cautious but for a crop sensor camera like yours it's more of a sensible option. An example of that would be:-

Focal length = 50mm, shutter speed = 1/100 sec.

User ID

sebastian wrote:

Thank you all. That was fast!
Got everything, but to simplify my queswtion, being a zoom? lens, shal I use it relating always as a 135 MM. regardless of the focal lens I'm using?
Is my understanding that the "rule" is because of the weight and lenth of the lens and shaking...
Thanks again
sebastian

The "rule" is NOT about the weight and length of the lens. Its about the image magnification of long lenses. Hand tremors make the image move around slightly on the sensor. A longer, more magnifying FL makes those many slight movements larger and faster, so you need a faster shutter speed to "freeze" them into an appearance of sharpness.

SuperflyTNT Loc: Manassas VA

larryepage wrote:

Sebastian...I think I understand what you are inte... (show quote)

The focal length is a physical relationship between the sensor plane. The “rule” is influenced by sensor size because it should be applied based on effective focal length. Although it’s not as important with advances in lens VR and IBIS.