Shutter speed rule of thumb

[tumblew33d]

I understand the basic rule of thumb regarding shutter speed and focal length when shooting hand held ie. recommended shutter speed is directly proportional to focal length - shooting at 300mm, shutter speed should be no lower than 1/300 sec etc. to avoid blur from camera shake.

I also understand that lenses perform differently on crop bodies than they do on full frame bodies i.e. 50mm lens on a 1.6x crop body provides the same field of view as an 80mm lens on a full frame body.

What I don't understand is why do people suggest that the crop factor on crop bodies should also be taken into account if the focal length itself isn't changing?

For example, I read someone suggesting that with a 50mm lens, it should be treated as an 80mm for the purpose of minimum handheld shutter speed on a crop body. Why?

I'm pretty new to all this, and I've been puzzling over it for a few days and thought I'd ask.

Thanks,

Jon.

[Mark_Cohran]

Camera movement is what cause the blurring of the image and it's relative to the enlargement of the image from the original size. The rule of thumb you described was developed based on using lenses on 35mm film cameras (full frame by default), therefore, assuming you're going to make the same size prints from your 1.6 crop factor camera as you made from 35mm film, you're going to have to take into account the smaller sensor size and the resulting magnification factor to achieve the desired print size. The amount of motion blur at the film/sensor plane and its subsequent enlargement is the key to understanding this.

Mark

[CyberDyneSystems]

Even though the lens does not increase focal length, you will be printing to paper sizes that are NOT 1.6 crops of standard sizes, in essence, you will be blowing up your crop to fit a standard paper size.

this is still magnification as compared to a full frame image taken with the same lens and printed to the same peice of photopaper uncropped, it just happens on the print side of things. This is why people disagree on this aspect, the 1.6X does change your feild of view to that of a longer lens on a full frame body,. the lens focal length remains constant but what do we do with these "cropped" (as compared to full frame) images we get with our APS cameras?

Since you are going to blowing up your images, then you need to take that into account for your "rule of thumb", just as you would take into account the print size or "blow up" you intended if you were shooting film. A larger print will show more flaws, more camera shake, so you need a better image, or faster shutter speed.

Thus the 1.6X-Factor would be added to yout "rule of thumb" if you happen to abide it.

[CyberDyneSystems]

Geeze Mark,. you typed much faster than me on that one! :)

[Mark_Cohran]

Shorter answer :)

[tumblew33d]

You guys certainly have nimble fingers!

Thanks for the lightning fast replies. What you've said makes a lot of sense, thanks for taking the time to enlighten me!

I have read a few posts that contradict each other regarding this. It's good to know exactly what's what.

Thanks again,

Jon.

[Hellashot]

I however do not agree with applying crop factors into the 1/focal length rule. You may notice some less sharpness if you print 12x18 from a 1.6x dSLR but you certainly wont notice any print quality issues when printing 4x6, 5x7, or 8x10.

[Mark_Cohran]

I however do not agree with applying crop factors into the 1/focal length rule. You may notice some less sharpness if you print 12x18 from a 1.6x dSLR but you certainly wont notice any print quality issues when printing 4x6, 5x7, or 8x10.

Many others agree with you, but as explained above, the basis for the thumbrule is the degree of enlargement from a given size recording medium, so it seems that your disagreement is with the thumbrule altogether. This is certainly a valid point, since many people (with practice and proper technique) can shoot at lower shutter speeds than recommended by the 1/focal length thumbrule, while others need to use higher speeds because they are not as steady as others. Personally, I think people need to figure this out for themselves, using the thumbrule as a basis from which to start.

Mark

[Curtis N]

Personally, I think people need to figure this out for themselves, using the thumbrule as a basis from which to start.Exactly.

There are no absolutes when it comes to motion blur. Doubling your shutter speed won't eliminate it, only make it less noticeable.

The trick is in taking all factors into account which might affect your steadiness, to determine a shutter speed which might give you an acceptable keeper ratio, to produce images with acceptable sharpness, at the print size you intend to make, knowing that in most cases you will need to compromise aperture or ISO which each affect IQ in their own way.

Nothin' to it. ;)

[tumblew33d]

I get what everyone's saying, however, when thinking about it some more I'm still confused. It might be time to dig out the old physics textbooks.

The way I was thinking about it was in terms of focal length being a physical quantity.

I imagine a stick pointing towards the object I'm shooting. The longer the stick, the higher the amplification of any shake.

2 sticks of the same length and identical in all other respects should show an identical amount of shake under identical conditions. This shake isn't being magnified on a crop body, just the field of view changed (cropped).

I'm thinking too much into this now, but am I thinking along the right lines, or have I got the wrong end of the stick (excuse the pun ;))

[SkipD]

As far as applying a "rule of thumb", the first two replies are precisely correct. If you are making the SAME SIZE print (of the entire image in both cases) from two cameras using the same focal length lens and shooting the same camera-to-subject distance, the print made from the smaller format will have more apparent motion blur because the original image size (the film or sensor size) has to be magnified more to make the matching print size.

That said, a "rule of thumb" is just that. Many folks need a faster shutter speed to eliminate camera/lens motion blur because they just can't hold the camera steady. Others can cut the "rule of thumb" in half because they are really good at holding a camera steady. Each photographer should really experiment with their own ability and create their "rule of thumb" for what minimum shutter speed to use.

Additionally, Image Stabilization (or its other names by manufacturers other than Canon) can help to solve the problem for many folks, further modifying the "rule of thumb" values for them. Note that IS will not "stop" movement of the subject to any degree greater than the actual shutter speed will, but it will make it appear that the camera was more steady than it actually was.

[Phil V]

I
I imagine a stick pointing towards the object I'm shooting. The longer the stick, the higher the amplification of any shake.

2 sticks of the same length and identical in all other respects should show an identical amount of shake under identical conditions. This shake isn't being magnified on a crop body, just the field of view changed (cropped).

To make your anology work, try this
Your identical sticks aren't being held at the end, rather on a pivot point close to the end, one of them will have a shorter 'back end' than the other (the crop). And so when viewed the shorter one will show less movement (at the back where the sensor is), however once this sensor has been 'blown up' to compensate for it's lack of size, the relative movement of the stick will have grown also. (I think).

Anyway this is all overcomplicating something that is 'a rule of thumb'. My wife has an amazingly steady hand and recently took a shot at 18mm (1.6 crop = 27mm ish) at 1/6 sec and it'll blow up to 12x10 no probs. I was amazed when I saw the exif info. I have fairly good technique and can usually better the rule of thumb by 1/2 - 1 stop. But I know many people who can't manage a sharp shot with normal focal lengths at focal length +1.

[RuggerJoe]

I get what everyone's saying, however, when thinking about it some more I'm still confused. It might be time to dig out the old physics textbooks.

The way I was thinking about it was in terms of focal length being a physical quantity.

I imagine a stick pointing towards the object I'm shooting. The longer the stick, the higher the amplification of any shake.

2 sticks of the same length and identical in all other respects should show an identical amount of shake under identical conditions. This shake isn't being magnified on a crop body, just the field of view changed (cropped).

I'm thinking too much into this now, but am I thinking along the right lines, or have I got the wrong end of the stick (excuse the pun ;))

At this point it has less to do with optical physices of the lens, and more to do whit what you are doing with the image the sensor produces once printed. A camera with a APS sensor does not produce a cropped print on a smaller sheet of paper. It produces a enlarged cropped print on the same size paper.

If you look at the poor picture I drew in paint maybe it will help. The camera shake is indicated by the arrow. While the arrows are the same size, it covers a bigger % of the height of APS sensor. If we print both pictures on the same size paper we will not get identical images. The arrow from the cropped sensor will be longer than the arrow printed on the same size paper from the full frame.

[tumblew33d]

Joe, thanks for taking the time to create that.

I'm a visual learner and that helped a lot. I've not seen an explanation like that anywhere else, so thanks a lot, I appreciate it!

Thanks to everyone who posted, there certainly are a lot of knowledgeable and helpful folk here:)

Jon.

[fitzhugh]

I'm quite new to all this and had not heard of that rule of thumb before. I had somewhere picked up that 1/60 was a rule of thumb for 35mm, maybe I just have shaky hands (or could have taken pictures I missed out on). Never took enough to know until recently.

I'd like help translating this for my a620. I don't know it's actual focal length, all I can find in the manual is "The zoom can be adjusted from 35mm to 140mm (focal length) in 35mm film equivalent terms." Oh, wait... on the front of the lens itself it reads "7.3-29.1mm 1:2.8-4.1"

I'm not clear on what to do with this info. Trying some test shots showed me:
yes, my hands are very shaky indeed, and yet the damage was less than I expected when I tried 1/8th at 7.3mm, at least on lucky shots.

My very basic questions:
Could someone please explain what is meant by 35mm equivalent, as well as suggest which numbers to base the rule of thumb on? Seems ridiculous to be shooting without a tripod at such slow speeds, and the camera's shake warning indicator (based not on a motion detector but just on shutter speed, I believe) warns at anything slower than 1/50th.

Thanks

[StewartR]

Fitzhugh, the 'reciprocal of the focal length' rule-of-thumb is aimed at 35mm cameras. So if you know what the equivalent focal length is for your camera, then you can use the rule-of-thumb.

OK, what's this "equivalent focal length" stuff? Well, your camera has a smaller sensor than a 35mm (full-frame) camera, which means that the field of view at any given focal length is smaller than on a 35mm camera - i.e. you get a field of view that is the sme size as you'd get with a longer lens on the 35mm camera. Read the first couple of posts in this thread: 10,000,000 posts on the X-factor (http://photography-on-the.net/forum/showthread.php?t=45388) for a far better explanation than I could give you.

Anyway, from the data you've supplied it seems that the field of view on your a620 at 7.3mm focal length is the same as the field of view on a full-frame camera at 35mm focal length. So your "X-factor" is roughly 5. And, if your hands are averagely steady, it implies you need a shutter speed around 1/30th at the wide end and 1/125th at the tele end in order to avoid camera shake.

[fitzhugh]

OK, what's this "equivalent focal length" stuff? Well, your camera has a smaller sensor than a 35mm (full-frame) camera, which means that the field of view at any given focal length is smaller than on a 35mm camera - i.e. you get a field of view that is the sme size as you'd get with a longer lens on the 35mm camera.

I'll go read that thread, but no, you explained it perfectly :) Considering how shaky MY hands are I should double the speed. All the more reason a tripod is an important purchase!

[I Simonius]

I understand the basic rule of thumb regarding shutter speed and focal length when shooting hand held ie. recommended shutter speed is directly proportional to focal length - shooting at 300mm, shutter speed should be no lower than 1/300 sec etc. to avoid blur from camera shake.

I also understand that lenses perform differently on crop bodies than they do on full frame bodies i.e. 50mm lens on a 1.6x crop body provides the same field of view as an 80mm lens on a full frame body.

What I don't understand is why do people suggest that the crop factor on crop bodies should also be taken into account if the focal length itself isn't changing?

For example, I read someone suggesting that with a 50mm lens, it should be treated as an 80mm for the purpose of minimum handheld shutter speed on a crop body. Why?

I'm pretty new to all this, and I've been puzzling over it for a few days and thought I'd ask.

Thanks,

Jon.
yes you are more liely to notice camera shake using a 200mmlen on a crop body thanon FF because it acts like a 300mm (280) lens

[SkipD]

yes you are more liely to notice camera shake using a 200mmlen on a crop body thanon FF because it acts like a 300mm (280) lensYou really must add "on a 35mm camera (or "full-frame" DSLR) body" to your statement. That way, newbies who don't understand the "crop factor" thing won't be thoroughly confused by the statement.

[I Simonius]

You really must add "on a 35mm camera (or "full-frame" DSLR) body" to your statement. That way, newbies who don't understand the "crop factor" thing won't be thoroughly confused by the statement.

to quote the OP
"lenses perform differently on crop bodies"

If YOU want to explain that to people feel free:rolleyes:

[SkipD]

to quote the OP
"lenses perform differently on crop bodies"

If YOU want to explain that to people feel free:rolleyes:I do that frequently.

I just feel that those of us who have lots of posts in the forums here (and are likely seen as being "gurus" by the forum newbies) shouldn't use open-ended statements that can be confused easily by the newbies. :p

[Mike R]

As others have mentioned, the rule is a guidline, you need to know your own limits. At 300mm I shot at 1/640! The best thing to do is experiment and learn your limts before that all important shot.

[Stump]

My experience is the "rule of thumb" thing is off bigtime. It probably depends on the person, but I dont need 1/50th shutter to shoot at 50mm. I went looking at Christmas lights the other night, I used 1/13th shutter at 55mm and most of the shots are fine. Out of 30 I probably have 4 that were blurry.

[davidmigl]

This might have been asked before, but does the rule apply all the way down to wide-angles? If I had a peleng 8mm fisheye, could I get by with 1/8 sec?