Consistently sharp photos in 3 steps

Michelle Peeters wrote on Tuesday 16 January 2018 at 09:17  | reply

@Arthur: de cropfactor heeft inderdaad geen invloed op de werkelijke brandpuntsafstand, wel op de vergrotingsfactor. Een 70mm objectief op een cropcamera heeft immers een beeldhoek die overeenkomt met de brandpuntsafstand vermenigvuldigd met de cropfactor; een 70mm objectief op een 1,6 cropcamera levert dus een beelduitsnede op die overeenkomt met 113mm (als de afstand tot het onderwerp gelijk blijft, natuurlijk). Het lijkt dus of je met een langer brandpunt aan het fotograferen bent waardoor de bewegingen op afstand dus ook evenredig toenemen! Dat is de reden waarom je toch rekening moet houden met de cropfactor om de minimale sluitertijd uit te rekenen.

Michelle Peeters wrote on Tuesday 16 January 2018 at 11:19  | reply

@RAWshooter: nowadays, isn't the distance from your front lens to your sensor equal to the distance from your front lens to your film (in the past)?

Arthur Wittendorp wrote on Tuesday 16 January 2018 at 11:46  | reply

@Michelle:
As you yourself already indicate, it seems as if you are photographing with a longer focal length. In reality, you are still photographing at 70mm. By using a smaller sensor (crop sensor), you only get a crop compared to a full-frame image. The myth that using a smaller sensor also increases the motion factor. That is complete nonsense.

@RAWshooter:
You are absolutely right. The focal length no longer says anything at all about the distance between the front lens and the sensor/film. It only says something about the angle of view used for photographing. 35mm, for example, has an angle of view of 63.4 degrees, 70mm an angle of view of 34.3 degrees and 12.4 degrees.

@Arthur: I’ve come across a discussion about shutter speed in relation to focal length on the internet before. What I understood from it: whether a photo is sharp or blurry depends, among other things, on the size at which you view a photo. A photo that has some motion blur (whether it’s the camera and/or the subject doesn’t matter for now) can look sharp at a very small size. You only start to see it (or "experience" it) when the photo, and therefore the pixels, are enlarged sufficiently. A photo from a camera with a crop factor does indeed make a kind of crop compared to a full-frame image. However, if you then enlarge this photo to the same size as that photo from the full-frame, every pixel has therefore become 1.5x larger than that of the full-frame (at least if the sensors have equally sized pixels). Your photo will therefore appear blurry sooner. Agree?

geerjanssen wrote on Tuesday 16 January 2018 at 12:25  | reply

@Arthur Nice that you point this out, I immediately went to your site and enjoyed your work, what really appeals to me is that the photos are very natural (no messing around with Adobe to make something more of them)

Michelle Peeters wrote on Tuesday 16 January 2018 at 12:49  | reply

@RAWshooter: with a crop factor, you do bring the subject closer! That's why a crop camera is also popular among wildlife photographers; their telephoto zoom gets the subject even closer! And you immediately see every small movement reflected in your image. The same effect as with macro photography, where you actually can't do without a tripod. That's how I've always understood it and that's how I read it on other (reliable) sites too!

Michelle Peeters wrote on Tuesday 16 January 2018 at 12:53  | reply

@RAWshooter; I didn't claim that either!

Michelle Peeters wrote on Tuesday 16 January 2018 at 13:14  | reply

@Jos: indeed a nice discussion (I’m learning from it too!). Thanks for your input, this is another fun one.

Jos: it's about motion blur: The blur that occurs because the front lens is not completely still during the exposure. And that really is an absolute concept. Exactly still means exactly still. A little movement is movement and therefore blurry. On a tripod, with no wind, using the self-timer/remote control, no flipping mirror, electronic shutter: then you are guaranteed to have no motion blur. Image stabilization helps enormously if you don't have (all of) those conditions.
Of course there are all kinds of degrees of motion BLUR, but sharp is sharp. And if we take that as our starting point, the size of the sensor (or how much a photo is cropped later) no longer matters.

Dear Michelle,

thanks for the info.
Question, does this then also mean that, for example for BIF, you should preferably photograph in S-priority?
I myself have been doing that for years, yet I hear that some of my friends photograph in A-priority....

Michelle, you explained it very clearly. The target audience can follow you. The know-it-all versions of the anonymous commenters are of no use to anyone. Actually, it shouldn't be possible to comment because you always get criticism. People who already (think they) know everything don't need to read it here anymore. It is just very annoying for the writer themselves to always be corrected, right? This is about basic information that many beginners are looking for. They have no use for those pointless discussions that arise underneath.

BIF = Birds In Flight....

@Michelle, well, that's fortunate then! It just seems very annoying to me that you write an article and then all sorts of people correct you on the content. And people who comment anonymously, that's simply a shame. I'd ignore them

Clear explanation again, Michelle!

Arthur Wittendorp wrote on Tuesday 16 January 2018 at 15:27  | reply

@Noor,
You can always take a sharp photo with 50mm at 1/50. Regardless of whether it is full-frame or a crop sensor. With a crop factor, you don't bring the subject closer. It is only a crop of a fulframe image. Michelle's statement is not correct. Especially @RAWshooter explains it well in the above-mentioned reactions!

@Geerjanssen
Thanks for your compliment

@Lenie
If the story is correct, you hear that nobody will start a discussion. Unfortunately, Michelle's statement is not correct. In my opinion, there is nothing wrong with a good discussion as long as we continue to respect each other!

Michelle Peeters wrote on Tuesday 16 January 2018 at 15:37  | reply

@Kees: what does it matter if you don't have a tripod or support at hand: inhale, exhale halfway and then take the photo. Apparently you're 'the most stable' at that moment.

Without claiming that Wikipedia is always 'right', here is a link to the secondary effects of a crop factor:
https://en.wikipedia.org/wiki/Crop_factor#Secondary_effects and a quote from it:

"The extra amount of enlargement required with smaller-format cameras increases the blur due to defocus, and also increases the blur due to camera motion (shake). As a result, the focal length that can be reliably hand-held at a given shutter speed for a sharp image is reduced by the crop factor. The old rule of thumb that shutter speed should be at least equal to focal length (in millimetres) for hand-holding will work equivalently if the actual focal length is multiplied by the FLM first before applying the rule."

Michelle's explanation is (therefore) the correct one. To calculate a safe shutter speed, you should (therefore) use 1/FF-equivalent focal length.
It also makes sense/is understandable, if you think of a much smaller sensor. For a superzoom compact with a 1/2.3" sensor, with a crop factor of 5.62, at, say, FL = 100mm = 562mm
FF-equivalent, a safe shutter speed of (rounded) 1/500 sec. still applies. (and not just 1/100 sec)

PS: I can imagine that it doesn't make much difference for an APS-C crop factor, but I know from personal experience that with my 1/1.7" sensor (crop factor 4.6) Nikon P7800 at 200mm FF-eq I really do have to shoot at 1/250, especially when I have VR turned off, and not 'only' at 1/40 sec.

Just to come back to the difference between problem (and therefore solution) #1 and #2:
* you (used to) solve the first one with shutter speed = 1/FL (FF-eq), but nowadays, with stabilization in the body and/or lens, you can 'gain' up to 6.5 stops (high-end m43); provided that problem #2 (movement in the subject) is not an issue
* you can't solve the second one with body and/or lens stabilization

PS: it's just like with university-level football (read: Barcelona):
making triangles, just like your tripod (which is also called tripod in English)

For problem #3 (aperture), you can perhaps take a look here and see for a particular FL what depth of field a particular f-number gives you:
https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{"c":[{"f":13,"av":"8","fl":50,"d":3048,"cm":"0"}],"m":0}

Fortunately, there are still people who want to have a discussion based on content. It's just a shame that only URL references are mentioned and no arguments of their own. Thinking for yourself and using your common sense is always better.

To help you with that, I will explain it once again in a different way:

Suppose you have a 50mm lens with a physical length of 3cm. And you have a 50mm with a length of 10cm. Would both (on the same camera) then be equally sensitive to motion blur? Of course not: The movement of your camera is caused by you holding it. That movement is "amplified" towards the front of your lens. Because the front lens moves, there is motion blur in your photo. The farther away your front lens is, the more movement you have. So the physical distance from the front part of your lens to the point where you hold the camera. For convenience (it doesn't come down to the centimetre), that is the middle of the body.

The phenomenon of focal length(-distance) plays no role in this whatsoever. That there is an old rule of thumb that equates the physical length of your lens with the focal length for convenience is understandable if you know the lenses of that time. It was reasonably accurate then, and such a rule of thumb is useful. But nowadays we have zoom lenses, very large fast standard lenses, etc. Just measure that 50mm f/1.2, the physical length is well over 5cm.

If you understand this, you also understand that sensor size is irrelevant. The only factor that determines how much movement occurs in the front lens is the physical length of the lens. At most, it SEEMS to be important, because you assume that some degree of movement always occurs. And when zoomed in, blur looks worse to the eye.
That is why the short shutter speed; in a short time you simply can move less. But it was about "consistent sharpness" and not about as little blur as possible. We want zero blur, not a little. And that is quite possible. A photo with motion blur has by definition failed. The blur covers the entire image. That is therefore something completely different from a moving object in an otherwise sharp photo.

Regarding all those other websites that do take the crop factor into account and (much more importantly in my opinion!) ignore the physical length of the lens: Does a statement automatically become true if you keep repeating it often enough? Because that is what happens. No one can determine what the scientific evidence for this rule of thumb is. It simply does not exist and cannot be created either.
A great many people do not feel like thinking for themselves and blindly copy what they find elsewhere. There are plenty of examples where that goes completely wrong in the world.
Somewhat philosophically: Do you want to believe or do you want to know?

I want to know and understand, which is why I think for myself. That is a choice, but everyone can make it. It would just be nice if I were left to my own worth with that choice and not dismissed as a contrarian or unreliable because I respond anonymously. That is very unfriendly.

I think it's a good story. I always teach my students the 1/focal length rule as well. With the added note that a number of additional factors also play a role, such as image stabilization and how steady your hand is at that moment.

So just adjust this rule according to your needs. I once had a student who had been a sniper and he could still take a sharp handheld photo at 200mm with a shutter speed of 0.5 seconds. Everything is relative.

Hello Ms Peters,
thank you for your article, it is always good to refresh certain things.
I do still have a question and it concerns this comment:

So if you have a 50 mm f/1.4 lens, it only starts to perform at its best (in terms of sharpness), at an aperture of f/2.8 or f/4 or higher.

I have been pondering for a while about buying a 50 mm. f1.8 prime lens and the comment above got me thinking.
What is actually the added value of such a lens if you have to start taking photos with an aperture that lets in the same amount of light as my 18-50mm kit lens. ?

I am probably making a mistake in my thinking, because I am not technical at all and I hope that you can explain this to me.

Thank you very much in advance for your answer.
kind regards
José

Michelle Peeters wrote on Tuesday 16 January 2018 at 19:32  | reply

@Evert: read through the article General camera settings for beginners and especially the paragraph about the best autofocus mode.

100 wrote on Wednesday 17 January 2018 at 02:44  | reply

@RAWshooter

You have to compare apples with other apples and not with pears, then you will see that points of view that seem different are not that different. With sharpness, for example, the relationship between pixel size and angular displacement plays a role, but there are many more factors.

To stick with your example of that 50mm lens, the following:
I can mount that 50mm lens on both FF and crop, and that makes the physical length irrelevant because the distance between the front element and sensor is then the same in both cases.

Suppose that both cameras also have the same number of pixels, the pixels of the FF camera are then larger than those of the crop camera and can therefore have a larger angular displacement at pixel level, or tolerate slightly more movement.

If you print the photos from both cameras at the same size, the pixels from the crop camera are enlarged more than those from the FF camera and the blur is also enlarged. In that specific case, Michelle's statement is correct.
The difference in this case is that the angle of view of the photo on crop is different from that on full frame. 50mm on 1.5 crop gives an angle of view comparable to 75mm on full frame.

Make the same comparison with the same lens between a 1.5 crop camera with 20 megapixels (for example a Nikon D500) and an FF camera with 45 megapixels (for example a Nikon D850) where the pixels are therefore the same size, then the sharpness will be the same because the pixels are enlarged to the same extent.
In that specific case you therefore need the same shutter speed for both cameras for the same sharpness.
A 1.5 crop of a D850 at the same shutter speed, aperture and ISO gives the same photo as a D500, both in resolution, as in sharpness, as in angle of view, as in depth of field, as in noise.

The difficult thing with this kind of comparison (equivalence) is that it only applies if all other factors are exactly the same. If not, you quickly end up comparing apples with pears and discussions arise like in the thread above, where both points of view can be correct in specific cases but not as a generally applicable rule.

As for the old rule of thumb that the shutter speed must be at least 1 divided by focal length, I think that rule of thumb has little value these days. In just under 20 years, the number of megapixels on a sensor has increased by a factor of 10 or more and that affects the minimum shutter speed for sharp photos.

RAWshooter’s statement keeps occupying my thoughts
In my opinion, it is easy to undermine. Suppose you manage to take a perfectly sharp photo with a zoom lens zoomed in to 70mm and a shutter speed of 1/70. Why is it then that you rarely manage to take a sharp photo with the same equipment zoomed in to 200mm and a shutter speed of 1/70? The physical length of this lens remains the same, only the zoom changes.
In my opinion, the explanation is simple and in fact a repetition of an earlier argument: if you zoom in further, motion blur becomes noticeable sooner. If you were to zoom in extremely on the first photo, you would probably also see that the photo is not 100% free of motion blur.

If you really managed to keep the camera perfectly still (which of course does happen every now and then), then that rule of thumb concerning focal length and shutter speed would be unnecessary. The fact that this rule of thumb does indeed make sense has to do with the fact that it is rarely possible to hold the camera 100% still in your hand and you make the motion blur "invisible" by using fast shutter speeds.

RAWshooter is essentially saying that this is not possible: the photo is either sharp, or it has motion blur (free translation of: We want zero blur, not a little. And that is perfectly possible too.). If that were true, then there would have to be one shutter speed that you must stay below to prevent motion blur, regardless of lens size or focal length. And that statement seems easy to disprove experimentally to me.

P.S. This text is a combination of knowledge I have acquired on the internet and thinking for myself

Michelle Peeters wrote on Wednesday 17 January 2018 at 11:58  | reply

Nando Harmsen (someone who really knows what he's talking about) explains the crop factor in relation to shutter speed perfectly on his site.

Quoted here:

Although a crop factor has no influence on the actual focal length, it does influence the magnification factor. A 50mm lens on a crop camera does, after all, have a field of view that corresponds to the focal length multiplied by the crop factor; a 50mm lens on a 1.6 crop camera therefore produces a crop that corresponds to 80mm (if the distance to the subject remains the same, of course). It therefore seems that you are photographing with a longer focal length, causing movements at a distance to increase proportionally as well. That is why you need to take the crop factor into account when calculating the minimum shutter speed. The rule should therefore look like this:

shutter speed = 1 / [focal length * crop factor]

@ RAWshooter. I would like to respond to that: I had not considered that the core of the story. But I think that is correct: the physical length of the lens is more important than the focal length. But the conclusions you draw from that and the continuation of the argument are incorrect. And that was what my response was about.

Michelle Peeters wrote on Wednesday 17 January 2018 at 23:54  | reply

@Donald: what can be helpful if you have trouble seeing it (I indeed also often find manually focusing not an option) is setting one focus point in the center (or a number of them, but in the center) and turning on the beep in the camera settings. Your camera will then beep as soon as it has focused properly. Because you know that your focus point is always exactly in the center, you can 'aim' more easily and also work a bit by feel. Usually you're then fine with your focusing on AF.

100 wrote on Thursday 18 January 2018 at 02:35  | reply

@RAWshooter

“I don’t see a rebuttal anywhere to my example of the physical lengths of the 50mm lenses, for instance. And that is precisely the essence of my story.”

There you go. The physical length of a lens is not relevant.
It’s about the angle of view.
If the angle of view is the same, then the sensitivity to motion blur is also the same, whether the lens is 3cm long or 10cm, it doesn’t matter.

As an example, two actual lenses:
A Sigma 35mm f/1.4 Art is 94mm long and has an angle of view of 63 degrees
A Canon EF 100mm f/2 is only 74mm long and has an angle of view of 24 degrees

If I shake while taking a photo and the lens shifts by, say, 1 degree, then the movement in the photo is 1/63 of the photo with the 35mm lens and 1/24 of the photo with the 100mm lens.
Which photo will then have the greatest blur?
With your reasoning, the 100mm lens would do better than the 35mm lens because the 100mm is physically shorter.

You say you don’t want to believe but to know.
Fine, test your hypothesis in practice with real lenses and see whether the results correspond with your hypothesis. My experience is that I can still get reasonably good results handheld with my 35mm f/1.4 Art at 1/30, but I can’t do that with a 100mm lens.

Michelle Peeters wrote on Thursday 18 January 2018 at 13:21  | reply

@RAWshooter: motion blur occurs because you yourself move (unintentionally), not because of movement of the front lens!

The 1 divided by the focal length of the lens dates back to the days of film and is outdated. There are more factors that come into play nowadays, such as crop factor, image stabilization, sensor resolution.

See this video, item#3: https://m.youtube.com/watch?v=IsWGkUT5A_Y

Michelle Peeters wrote on Friday 19 January 2018 at 00:03  | reply

@Donald: as far as I know, nothing like that exists. But I could be wrong...

100 wrote on Friday 19 January 2018 at 02:37  | reply

@RAWshooter

I thought I had given a fairly clear substantiation, but fine, here it is again.

If I shake while taking a photo and the camera moves 1 degree during the set shutter speed, then:
1 - At an angle of view of 63°, the image shifts by 1/63 of the image.
2 - At an angle of view of 24°, the image shifts by 1/24 of the image.
1/63 is smaller than 1/24
This is basic mathematics, which is difficult to deny, surely.
The smaller the displacement, the sharper the photo, that also seems irrefutable to me.

Conclusion from the substantiation:
The lens with the widest angle of view produces the sharpest result with equal amounts of shake.

Now apply this to the dog's tail from your example.
If both tails rotate by 10°, the tip of the longest tail will cover a greater distance in centimetres, but the angle of rotation remains the same. The key is that the displacement is not expressed in length, but in degrees of arc, and you do that because camera movements are rotational movements.

If I move the camera in a straight movement, for example 1mm to the left, then the front of the lens also only moves 1mm, it is only with a rotational movement that a difference arises between the front and the back.

The longer the lens, the more the front moves during a rotational movement, that's true, but light does not travel through a lens in a straight line, the light is refracted again by each lens element. The many different glass elements in a lens then create a complex path. The result of all those refractions is that the final image that falls on the sensor has a certain angle of view, and that angle of view determines what is still called the focal length, even though it actually hasn't been that for a long time.

If you look at the specifications of lenses, you will see that every 35mm lens has an angle of view of approximately 63°, regardless of the physical length of the lens, and the same applies to other focal lengths.
The difference in length is due to the optical construction. Modern retrofocus lenses are more complex and have more lens elements than the older types and are therefore often longer. Long telephoto lenses, on the other hand, are often shorter than the focal length. For example, an EF 400mm f/4 DO IS II is only 233mm long.
Yet the angle of view remains the same regardless of the physical length, and that is the determining factor for motion blur caused by shaking, as explained above.

Now compare those 233mm with the 94mm length of my 35mm lens, that's about 2.5 times as long.
According to your reasoning, if I can just about take a sharp enough handheld photo with my 35mm lens at 1/30, I should be able to shoot sharply with that 400mm lens at 1/75.
I can't do that, and that's because the angle of view of a 400mm lens (even though it is only just over 200mm long) is only 6 degrees (approximately 9.5% of the angle of view of a 35mm lens). So I need at least 1/300 with a non-stabilised 400mm lens for sharp photos, and that is also what I experience in practice.

But anyway, as I said earlier, you don't have to agree with the argumentation I give, theory is nice, but practice is what counts, so just test it yourself.

Michelle Peeters wrote on Friday 19 January 2018 at 10:51  | reply

If you look at the animated gif images on Nando Harmsen's site, you can see and understand exactly how it works.

1st image:
The angle of view (focal length) determines how clearly the camera movements become visible. The larger the angle of view, meaning a shorter focal length, the smaller your subject becomes, and the less such a movement will be visible. In that case, the shutter speed does not need to be as fast.

2nd image:
The same movement but now with a telephoto lens. The magnification of the movement is nearly equal to the increase in focal length. If the previous one had been with a 50mm focal length, this is what a 200 mm would show: with a movement that is amplified 4x. Since the movement in the image is much larger than with a shorter focal length, a faster shutter speed is also needed to ‘freeze’ this movement.

What about the crop factor? Does that rule still apply? Although a crop factor has no influence on the actual focal length, it does influence the magnification factor. A 50mm lens on a crop camera does after all have an angle of view corresponding to the focal length multiplied by the crop factor; a 50mm lens on a 1.6 crop camera therefore produces an image area corresponding to 80mm (if the distance to the subject remains the same, of course). So it seems that you are photographing with a longer focal length, meaning that movements at a distance also increase proportionally. That is why you need to take the crop factor into account when calculating the minimum shutter speed.