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03-19-2015, 10:37 AM   #1
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Focal length = min. shutter speed = ff crop?

So I have always wondered this...

The rule of thumb that your focal length should be the minimum for shutter speed. i.e.

I have my 17-50 lens. I am zoomed into 40mm lets say. So in FF format I am at 60mm.

With that rule being applied, should my minimum shutter speed then be 1/60 or 1/80?
Do you apply the rule to the FF focal length, or the cropped labeled focal length.

I hope my question makes sense.

55mm 1.4 lens being used. in FF that is 82.5 mm. Should my shutter be min. 1/60 or 1/125?

03-19-2015, 10:47 AM   #2
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This rule used to hold in the film days. For APSC, people modified it to multiply by the crop factor. In my experience, this is no longer enough. I think it is because the pixel density of modern cameras is so high.
So if I am using 1/(1.5*focal length), I enable SR. Or I use a monopod, tripod (without SR, bonus points for 2 sec timer with MLU). For normal and wide angle lenses, I still rarely go under 1/80. You might be interested to know that if you use a wide angle manual lens, even if you input the focal length, the camera will still try to keep shutter speed above 1/125. I guess Pentax decided that is the "minimum" for older lenses (keeping in mind older lenses were rarely wider than 20mm)

Basically, it comes down to how steady your hands are, how effective SR is, and how high your motion blur standards are. In the end, the only way to get a perfectly sharp photo is to use a tripod, MLU, remote trigger with timer, and lights. Everything else, you start making compromises and its a balancing act.
Btw, you can search the PF, there is a nice guide on photograph stance and how to hold the camera. It may sound silly at first, but it can definitely help if you practice a little. So many people introduce motion blur by the way they press the shutter button, hold their camera gear
03-19-2015, 11:03 AM   #3
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As @Na Horuk says that 1/focal length is from film. I have heard people say that on APS-C you should multiple by the crop factor. And others say focal length is focal length so just use the old rule.

But there are other factors involved, particularly SR which reduces the speed needed. And the increase in sensor resolution which increases the speed needed. And the rule was never (IMHO) linear because a wide angle lens could be used at far less than 1/focal length but a long tele might not be usable at far more than 1/ focal length. Add in the variable for how steady your hands are plus how good your technique is and maybe it is just as easy to use the old rule of 1/focal length.

In short, too many variables to say definitely for all people. I use 1/ 2* focal length if I can. I would suggest starting with 1/focal length and increasing the speed until you get good results. Then you have the "rule of thumb" that works for you.
03-19-2015, 11:26 AM   #4
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I too was schooled in the 1/focal length of the film days and still think in those terms when shooting manual.
However, I've found that shake reduction can compensate for a stop or two, (at least), especially if you're well
braced. In ideal situations I might be able to shoot 1/4*focal or greater. In practice, I tend to push as far as
I can as need, then check the playback to see if I'm getting the shot without motion blur and then correct
exposure if necessary. Instant review really is one of the greatest strengths of digital over film, (and one of
it's greatest weaknesses as well; it fosters complacency).

03-19-2015, 11:28 AM   #5
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Assuming the shake is a translation motion parallel to the FF and cropped sensor, the cropped sensor motion relative to the sensor size will be larger--thus to be the same fraction of the image you would increase the shutter speed by the ratio of their respective lineal sizes--i.e.,the crop factor.

So at 40mm (both cameras lenses actual FL=40) you would use 1/40s in FF and 1/60s in 1.5 cropped sensor.

The rule of thumb should be modified depending on how steady you hold the camera, the subject, etc, and if you decide your value for FF is 1/(2FL) s, then it is 1/(1.5x2FL) s, or =1/(3FL )s.

As a general rule of thumb/starting point I would think picking 1/(2FL) s for 1.5 cropped sensor is a reasonable. If you are very steady make it 1/FL s.

Of course this w/o SR. W/ SR my guesstimate is I can do reliably 10/FL s to 20/FL s (on a 1.5 cropped sensor) for 8"x12" print.** But I suspect I have a very stable stance.

___
** I doubt if this rule remains the same when times are so long as to include a heart beat, or roughly 1/3 s. Thus my thinking [and experience] suggests the rule is actually not short enough for wider FL lenses--the reverse of other peoples (earlier post) experience.

Last edited by dms; 03-19-2015 at 11:43 AM.
03-19-2015, 11:45 AM   #6
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There used to be a photographer on here that recommended a range between 1/2FL to 1/5FL.

If i'm shooting in the theatre at actors, i try to use a min of 1/160s, but that often still give me blur on hands and arms.

I have a friend who must be math challenged or she would not recalculate for different zoom FL. She was having a lot of blurred pictures and blamed it on the camera. So in some frustration, i told her to just use 1/500s. So about 2 weeks later, after i forgot about my advice, she thanked me for the tip and how much sharper her pictures are - she uses a D7000. So the lesson here is: if you are out of doors and have plenty of light, use 1/500s, you'd be amazed at how good that looks

Reminds me, i was out on a whale watching boat with some sizable chop on the water. The boat was moving like crazy. So i bumped up the shutter speed to 1/2000 and didn't have much hope. But the pics came out great.

Its funny how our cameras are so programmed to give us the minimum shutter speed all the time.
03-19-2015, 11:47 AM   #7
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My primary use is concerts. VERY low light, high iso, usually wide open at 2.8 or sub 2.8.

also thanks for all the replies
03-19-2015, 02:08 PM   #8
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I use 1/(2*fl) when I'm shooting most of the time and that works. If I get into a situation where I need to go 1/fl or less (I've had success slower) technique becomes critical, steady hand and still subject. Outdoors in strong light, don't pay a lot of attention to it unless I'm stopped way down. In those cases you're usually more worried about overexposure anyway, so fast is good.

03-19-2015, 03:21 PM   #9
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QuoteOriginally posted by jatrax Quote
As @Na Horuk says that 1/focal length is from film.
Indeed and the rule works pretty well, though we all pushed the limits back then. I regularly would shoot as slow as 1/15s back then with a 50mm lens on my film cameras and still do. It is not hard with practice.

What I tell people now is to take advantage of the quick feedback that digital cameras provide. In dim light, chimping is a good thing! For a given subject with today's SR systems you may be able to far exceed your expectations with a little practice. My claim to fame is shooting at 1/8s with the 85mm Jupiter-9 on my K10D.


Steve
03-19-2015, 03:33 PM   #10
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QuoteOriginally posted by rzarector Quote
My primary use is concerts. VERY low light, high iso, usually wide open at 2.8 or sub 2.8.
Then you might be forced to go to 1/20 or even longer. Good idea to practice handling the camera, bracing against things.. or sneaking in a tiny tripod
03-19-2015, 04:05 PM - 1 Like   #11
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Go with a higher shutter speed at concerts, rzarector. The grain from high ISO noise can be forgiven/dealt with in post, blurring not so much unless part of an intentional effect.

Handheld attempt of the Lamb of God singer with the DA* 50-135 at longest focal length, 1/1000s. ISO is 10,000 on the K-S1. No depth of field to speak of at f2.8, but his motion is frozen.



This one of a Black Sabbath cover band taken with a Tamron 17-50mm is at ISO 25,600:


Last edited by clackers; 03-19-2015 at 10:00 PM.
03-20-2015, 01:00 PM   #12
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QuoteOriginally posted by clackers Quote
Go with a higher shutter speed at concerts, rzarector. The grain from high ISO noise can be forgiven/dealt with in post, blurring not so much unless part of an intentional effect.
+1. You need to deal with two different motion types. Camera shake caused by the photographer and blur caused by the subject moving. No matter how good your technique is if your subject is moving then it is subject motion speed you need to deal with. You can fix ISO noise (to some degree) you cannot fix blur.

You need to decide for each shot which motion is the most important. If the subject is not moving then camera shake is the deciding factor in determining the minimum shutter speed. But if the subject is moving then most times the speed needed to freeze the subject is the critical factor.
03-20-2015, 01:28 PM   #13
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The rule is as follows

From film, printing a full frame 35mm negative to an 8x10 inch you shoot at 1/focal length.

The basis is that with reasonable technique, this is sufficient to result in blurr in the enlarged image that has a point of light is turned into either a short line or a circle less than 1/100 of an inch.

If this seems to sound like depth of field, and circles of confusion, your right. The 1/100 inch on an 8x10 print as the definition of acceptably sharp is the same.

So, for a crop sensor the rule is 1/1.5 x focal length, but only if you print 8x10 (ok I'll give in and consider 8-1/2 x 11 ) but if you crop further, or enlarge more, you need to consider higher shutter speeds
03-20-2015, 02:41 PM   #14
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The mentioned rules of thumb was correct for SLRs (but only for these with well balanced internal moving parts and good mirror slap damping). With many range finders you could use much longer times.

But this has changed a bit in the eighties with the introduction of motors moving levers for mirror and shutter. To compensate the torque of these, you would need a second unit turning everything in opposite direction, as it is done in high tech car motors to damp vibrations (specially in case of odd number of cylinders).

The vibrations of my K200D and *istDS when shooting feels multiple times what I feel with my ME Super and Super A. Despite the higher weight of the bodies.
03-21-2015, 05:00 AM   #15
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QuoteOriginally posted by Lowell Goudge Quote
The rule is as follows

From film, printing a full frame 35mm negative to an 8x10 inch you shoot at 1/focal length.

The basis is that with reasonable technique, this is sufficient to result in blurr in the enlarged image that has a point of light is turned into either a short line or a circle less than 1/100 of an inch.

If this seems to sound like depth of field, and circles of confusion, your right. The 1/100 inch on an 8x10 print as the definition of acceptably sharp is the same.

So, for a crop sensor the rule is 1/1.5 x focal length, but only if you print 8x10 (ok I'll give in and consider 8-1/2 x 11 ) but if you crop further, or enlarge more, you need to consider higher shutter speeds
This.

How large you are going to print (or how much you'll crop on screen) is the key. For a web sized image you can get away with some motion blur.

Also, someone with steady hands and a good stance can get away with slower shutter speeds (for stationary motifs). When doing everything right I can get sharp images with my DFA 100mm at 1/10th - with SR enabled. Likewise, someone suffering from e.g. tremors will probably need faster shutter speeds than this "rule" indicates. There is no way around experimenting to learn what you can get away with.

For action shooting you probably want 1/500th or faster no matter the focal length.
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