Question about Sigma 15-30mm f/3.5-4.5 EX Aspherical DG DF for Pentax AF

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I am having problems with my Sigma 15-30mm EX lens. The aperture doesn't work properly at all focal lengths. At 15mm doesn't work but at wide open with the aperture. Sometimes stops down from 20-30mm. Need help.

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Posted on Jan 01, 2010

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I have a tamron 28-200mm lens that have a aperture ring at the back .. so is it possible to lock the aperture at f3.8 and shoot at 200mm focal ?? (this lens was f3.8- f5.6) by the way i was using a n


If you're using a Nikon camera, you want to lock the aperture ring at its smallest setting (largest f/number). You can control the aperture from the camera body, the same way as on a lens without an aperture ring.

This has nothing to do with the focal length. You can shoot at any focal length from 28mm to 200mm.

Feb 10, 2014 | Cameras

1 Answer

Sigma lens won't turn past 1.3


Make sure you are zoomed out all the way, many lenses when zoomed in will only let you stop the aperture down so far at certain focal zoom lengths.

Jun 01, 2012 | Sigma 30mm f14 EX DC HSM for Minolta

1 Answer

Focus out problem in canon 50d while using 24-70mm lens?


If by a "normal" lens, you mean a 35mm or 50mm fixed focal length - often called "prime" lens, that is to be expected. The additional and internal rotating optical elements all contribute to loss of clarity, color loss, and increased chromatic aberration that starts to become noticeable when compared to use of a prime lens. It's a trade off; less number of lenses to carry and lower cost when using wide angle zoom lenses as opposed to a prime lens for even just a few of the focal lengths offered by the wide angle zoom types.

You can minimize the unwanted effects by staying away from both the extreme wide angle and zoom focal lengths as well as the widest aperture settings. If you can stay 2 or 3 stops smaller from wide open, you can limit these destractions from your pictures. This is recommended advice for nearly every lens: Keep away from the extremes.

Good luck!

Jan 08, 2012 | Canon 24-70mm f/2.8 Lens

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Lens will not change aperture setting.. it's stuck on F4. Should be able to change to F2.8 Michael


You'll notice that the maximum aperture is specified as f/2.8-4.0. The lens has a maximum aperture of f/2.8 only at the 17mm focal length. At the 35mm focal length, the maximum aperture is f/4.

Does the lens open up to f/2.8 when you zoom out to 17mm?

Feb 17, 2011 | Sigma 17-35mm f/2.8-4.0 EX Aspherical HSM...

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How do you take a pic with the Nikon d60 where the background is blurred?


You're trying for what's called a narrow depth of field. DoF is controlled by three factors: distance from camera to subject, lens focal length, and lens aperture. The closer the camera is to the subject, the narrower the DoF. The longer the lens focal length, the narrower the DoF. The larger the lens aperture, the narrower the DoF.

Get as close to the subject as practical, and use as long a focal length as practical. I realize these two aims conflict with each other. For portraits, you want a focal length in the 50-90mm range and move in to fill the frame.

You want to shoot with as wide an aperture as you can. Unfortunately most lenses are not at their sharpest wide open. Also, the 18-55mm lens doesn't open up all that wide, f/3.5 at 18mm and f/5.6 at 55mm. To get the widest aperture, you can shoot in the P or A modes. If you don't want to leave the point&shoot modes, try using the Portrait mode.

Since you're not paying for film, I suggest you experiment with the different settings and shooting setups, moving closer and farther from the subject, using different focal lengths, and using different apertures, and see what results you get.

Nov 22, 2010 | Nikon D60 Digital Camera with 18-55mm lens

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I want to take a picture that is focused on the subject, while everything else in the picture is blurry


What you want is a limited depth of field. There are three factors that control the depth of field: subject distance, lens focal length, and lens aperture. The greater the distance, the wider the DoF. The shorter the lens, the greater the DoF. The smaller the aperture, the greater the DoF.

One problem with compact cameras is that they have very small sensors. This means that they have short lenses. And short lenses mean they have wide depth of field. This is often an advantage, in that more of the scene is in focus. Unfortunately, this works against you when you don't want a wide DoF.

At the short end, the S2's lens focal length is 6mm. This will put just about everything in focus. Even at the other end, the focal length is 72mm. With a 35mm film camera, most portrait photographers use lenses at least 85mm in focal length in an attempt to minimize DoF to draw attention to the face and blur the background.

Unfortunately, the best you'll be able to do is to set the camera to the portrait mode, get as close to the subject as possible, and zoom in as much as possible. I realize the last two conflict with each other, you'll just have to find the proper balance for whatever you're photographing.

Nov 18, 2010 | Canon PowerShot S2 IS Digital Camera

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My sigma 105 lens do not go to f2.8. it reaches only f3. tanx. macario sakay


If this is the Sigma 28-105mm f/2.8-4.0 as in the title, then the maximum aperture will vary with the focal length. It is probably only 2.8 when the focal length is zoomed to 28mm. It will be 4 at 105mm, and at focal lengths in between it will be in between.

Nov 17, 2010 | Sigma 28-105mm f/2.8-4.0 Aspherical...

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What mode do i use to make a person clear and the background blurry?


It's not the mode, it's the aperture. What you want is called a "narrow depth of field". Depth of field is controlled by three factors: focusing distance, lens focal length, and lens aperture. For portrait work you probably want a focal length in the 50-100mm range and an aperture as large (smaller f/number) as you can get.

How you get the large aperture is up to you. Probably the easiest is to select Aperture-priority mode and crank it as far as it goes.

I encourage you to experiment with it. If you can't get another person to help you, just put an object where you'd prefer to have a head. Use different apertures, and different focal lengths (moving closer or farther to compensate). It's not as if you're paying money for film and processing, after all.

Apr 21, 2010 | Olympus EVOLT E-500 Digital Camera

1 Answer

How to blur the background in picture taking?


Get another camera :-(

You want to reduce the depth-of-field so that the subject is in focus while the foreground and background are out of focus and blurred. Depth of field (DoF) is dependent on three factors: distance, lens aperture, and lens focal length.

The farther the subject, the deeper the DoF. If you take a picture of a distant mountain peak, the mountain behind that and sunlit the clouds on the horizon will also be in focus. If you get close enough to a flower, you might get the front petals in focus while the petals in the back might blur.

The smaller the lens aperture, the deeper the DoF. Landscape mode, for example, will try to use a smaller aperture in order to get everything in focus while portrait mode will try to use a larger aperture in order to blur the background.

The shorter the lens focal length, the deeper the DoF. This is the killer. Due to the small size of the image sensor, the EX-Z750 has a very short lens: 7.9mm to 23.7mm. Even at the telephoto end of the range, 23.7mm would be considered very wide by film photograpers. A 24mm lens would give film photographers a sharp shot from foreground to horizon and, unfortunately, you're seeing that as well.

Note that the DoF is dependent on the actual focal length, not the 35mm equivalent you may have read about. This is a law of physics, not something that lens designers can easily alter.

Mar 04, 2010 | Casio Exilim EX-Z750 Digital Camera

1 Answer

Can't get F3.5 aperture on the 18-135mm kit lense on d80


You may be shooting auto and there is too much light. If you want to be sure you are shooting with 18mm @ f3.5 then shoot with aperture priority (the shutter speed will adjust automatically). Ususally at a wide focal length you would want a small aperature (smaller f-stop) so this should not really be a problem.

Feb 14, 2009 | Nikon D80 Digital Camera with 18-135mm...

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