Aperture issue

[Watson2810]

Hi guys

Was trying to have a play around with my nikon p900 today whilst out on my motorbike. (Not whilst riding)
Wanted to have the bike as the subject with blurred back ground and couldn't seem to get the desired effect. But when I zoomed in on the wheel for example the background would be blurred. I used appeture priority mode and manual for this and dropped it to f 2.8.

I also was attempting shots whilst a friend was riding passed to get the blurred back ground but the desired look of fast movement but still failed. With this I used shutter speed at 1/1000 and appeture of f2.8 as it was the lowest but still everything was in focus. I no its a little dark and needed to up the iso on the moving image

Be great for some advice . Cheers guy

 

[The_Traveler]

My guess is that your camera has such a deep depth of field at a short focal length that everything will be in focus.
You will need to pan your camera using a slower speed so you blur the background wile the bike stays in focus.
The picture is underexposed because there is a very bright sky that takes up a good part of the frame, thus affecting the exposure and the side of the bike towards you is in the shadow.

 

[Watson2810]

Thank you. I did pan my camera at continously mode. But I might try next time to slow the shutter speed. See what happens. Appreciate the edit. I was just messing around to try and focus on the blurred effect. I'll get there in the end I've only just started. Thanks again

 

[The_Traveler]

no problem, glad to help if I can.

Lew

 

[Designer]

For the stationary shot, go to a telephoto setting, as long as it will go. A wide angle setting increases the DOF while a longer focal length will decrease the DOF (all other things being equal). When you shot the wheel, your lens was more toward the telephoto setting, hence the background blur.

For the motion shot, pan with the subject, and you'll need to experiment some with the shutter speeds. If you're good at panning (practice) then a slower shutter will blur the background (and foreground) more. If the shutter speed is too fast it will freeze everything, including the background. Also, the blur effect will be enhanced when the subject is moving at right angles to the camera. That is; pretty much straight out from where you are standing.

So if your focal length is kind of in the middle of the range (not wide, not telephoto) you should be able to get good shots at around 1/120 second or 1/160 or so. If your subject is blurry at those shutter speeds, then bump it up a bit.

 

[Destin]

The small sensor on your camera makes it hard to get a shallow DOF. The larger the sensor, the shallower the DOF.

 

[KmH]

DoF is about more than just the lens aperture or the just image sensor size.
You also have to be cognizant of the lens focal length and the point of focus distance.

So 4 factors determine the DoF.
Understanding Depth of Field in Photography

 

[photo1x1.com]

The kind of effects you are looking for are hard to achive without manual mode and/or additional gear (ND Filter)
The depth depends on

• the aperture (the smaller, the more shallow)
• the focal length (the longer the more shallow)
• the distance to your object (the closer, the more shallow)
• the distance object-background (the bigger, the more shallow)
• the sensor size (the bigger, the more shallow)

To be all honest with you - your camera has a rather small sensor, so what you need to do when you want to get that effect is: go as far away from your biking friend as possible and zoom all the way in so that he fills the frame (it is going to be difficult to follow him - if he is driving fast though ).

The other effect is even more difficult, and I´d consider it as one of the more advanced techniques in photography .

• Depending on the speed of your friend, you need a shutter speed of approx 1/5th as a starting point. Getting that in bright daylight is pretty difficult. You can either try after sunset, or you use an ND-Filter (those are nothing more than dark glass that reduces the light that gets to your sensor) - from what I read you´ll need 67mm - which strength you need depends on the time of day you are shooting. In bright daylight you need 3-6 stops (3 stops is callesd ND0.9 and 6 stops is called ND1.8 - so don´t be confused). The cheapest I found on b&h is for around 25US$ it is from tiffen, so not bad.
  
• Plus: you have to do it from the side (the distance camera - bike has to be the same for the complete process) and your friend has to be on the exact same position in the frame (in other words on your picture) for the time the image is taken. That´s pretty difficult and takes some practice - or a good video tripod so you can follow him easier.
  
• With a wideangle setting it is easier to not shake the camera enough to get your friend blurred too

 

[Braineack]

blur with motion, not DOF.

 

[astroNikon]

For sensor size reference.

The P900 has a 1/2.3 inch sensor. ( 6.16 x 4.62 mm size)
I have a P7800 - a 1.7" sensor, which I bought because I wanted a Deep Depth Of Field.
a camera like the d5300, d3x00, d7x00 is a 26.3 x 15.8mm "APS-C" sensor. Much larger than your p900 or my p7800.
A FX/Full Frame D610, D750 etc camera is 36 x 23.9mm.

As above replies state the sensors size is one determining factor in DOF though a major one in reference to a small to large sensor.

The chart below gives you a reference point of sensor size. The "crop" factor is related to the sensor size and the image circle that is produced from the lens.
https://lensvid.com/wp-content/uploads/2014/01/Sensors-size-01-01.jpg

Ahem!

.

 

[Ido]

Depth of field is not determined only by the f-number—the focal length and focus distance play a big role, as well.

You've probably read that your camera has a 24-2000mm zoom lens. That is not technically true, as its range of focal lengths actually starts at a mere 4.3mm and ends at 357mm. The difference between the advertised number and the real number is due to the size of the sensor in the camera. The 24-2000mm range is the "full frame equivalent"—which means, if you used a 35mm film camera or a full frame digital camera, you'd need a 24mm lens to get the same field of view as the P900 provides at the wide-angle end, and a 2000mm lens for the same field of view at telephoto.

Here's another shocker: the f-number is not really the aperture. We call it aperture just because it's easier, but the real aperture is a diameter measured in millimeters. The f-number is a ratio between the focal length and the aperture, so if you divide the focal length by the f-number, you get the aperture. The bigger the aperture, the shallower the depth of field.

Let's say you use a 24mm focal length and you set the f-number to f/4. The aperture, in this case, is (24mm / 4 = ) 6mm. But on your camera, the wide-end isn't actually a 24mm focal length—it's 4.3mm. So the aperture in this case, with the same f-number, is (4.3 / 4 = ) 1.075mm, so almost 6x smaller.

If you want a shallow depth of field, you need a camera with a bigger sensor. Then you'll use longer focal lengths for the same field of view, and if you maintain the same f-number, you'll have a bigger aperture. If you want to experiment with it, rent a Nikon D3300 and a 50mm f/1.8 lens, or similar kit (e.g. Canon Rebel-series camera + 50mm f/1.8 lens). The field of view may not fit with the shot you want to make, but at least it lets you try and play with a shallower depth of field.

 

[wfooshee]

Just to reiterate, do not confuse motion blur with depth of field.

Your first example, the stationary bike, would be a depth of field exercise. the problem is that the extremely short actual focal length of your lens effectively gives it an near-infinite depth of field, at least relative to what you're going for.

Your second example, the passing bike, would be a motion blur exercise. You do NOT want 1/1000 shutter speed for that, as it will freeze the frame. play with speeds around 1/250 at the fast end, and 1/125, even 1/60. move the camera with the subject, and keep moving after you shoot (follow through.) Motion blur will be more effective as the bike passes, not as it approaches, because very little camera motion is required when it's coming nearly straight at you.