I think I need a UV/polarizing filter. That should help stop the sky ‘blowing’ on bright days, right?

But there’s hundreds of the damned things from £1 to £50+. I’m guessing cheap ones will be worthless, so –

1) To fit Sigma 17-70 DC f2.8 lens (on a Canon 400D)
It says 72mm diameter on the lens, that’s the filter size, right? Will any filter the correct diameter fit?
(i.e. Are the threads/fittings all standard?)
3) UV/polarizing – is it the same thing? If not please explain. 🙂
2) Based on point 1, reccommend me a decent one please

Ta very muchly
Peter

UV and polarising are completely different things. A UV filter blocks UV light which had a tendency to make film “blue” in thin air (I think …). In the digital era they are no use whatsoever except as a way of pretecting your lens, at the cost of adding another layer of glass between the subject and the sensor. This is an argument a bit like whether to wear a helmet or not.

A polarising filter blocks .. err .. polarised light, in effect reflected light, so has the effect of cutting out reflections (no, really 🙂 ) and making the sky darker blue (so you get nice white puffy clouds on a dark sky). A polariser is really nice for landscapes (soem top landscape photogs leave a pol. on all the time) and mostly no use anywhere else.

I buy B+W filters, which are not cheap, but after paying <mumble> for a camera I don’t see the sense of sticking some blob of bottle glass on the lens.

Hope that helps 🙂

1)Yes, might be worth looking at ‘drop in’ filters eg cokin rather than a screw on eg Hoya – you won’t want the filter on all the time (see next bit for the reason).
2)No, you don’t want a polariser or uv filter, you want a graduated ND filter, or better still a set of them- basically these transmit more light on the bottom portion, thus for a given exposure value less light is transmitted from the top portion of the scene than the bottom. Googling will provide a better explanation than me.
3)As above, at a reasonable price point, Hoya or Cokin.

UV or skylight filters are these days normally used to protect your lens- much debate about the merit of using them. Hoya now do a ‘designed for digital’ filter marketed as a ‘digital lens protector’ which is supposed to use a thinner mount and fancy glass to maximise light ttransmission and minimise vignetting.

UV filter is to filter out some of the UV haze that you may get on sunny days, so that you get slightly better contrast. And more complex stuff I can’t be bothered to explain.

In all truth, they don’t make a lot of difference. Their best purpose is to protect the front of your lens. A UV filter may cost £10-20 for a decent one, whilst lenses can cost hundreds, if not thousands of pounds. If you scratch a filter, you can lob it and get a new one far more cheaply.

72mm diameter means any 72mm filter will fit, yes.

Polarizing is a completely different thing; it helps to reduce reflections from shiny surfaces, and can dramatically improve contrast, as well as darkening skies. It will reduce the amount of light coming through the lens. It is not a ‘leave on all the time’ filter.

Peter, why you not have a decent photography guide book?

As for good filters; Jessops own brand ones are decent quality, and very good value for money. The difference between brands, is the quality of glass. Nikon and Leica, for example, use top-quality optical glass, and superior coatings,which causes less distortion and aberration than cheaper glass. If you are a pro tographer, who has to have the very sharpest results possible, then you’d want to spend the money on the best stuff. In the real world, there is very little if no real discernible difference in the quality of pics.

So, yer Nikon and Leica at the top end, with brands like Canon and B+W close. Then you’ve got Hoya, which are very good, and do budget and posh versions. Jessops are among the cheaper options, and are very good, as I’ve said before (I understand they are made in the same factory as other brands, but a good few quid cheaper).

Peter – so you know, a 72mm dia Cicular Polarising filter (make sure you get cir-pol as normal pol won’t be much use on an AF DSLR) will not be cheap – budget for £50 absolute minimum.

Jessop’s own are good value, and if they don’t have the right size in stock i think the policy is to sell you the next cheapest brand name that theu do have in that size…which can be a real bargain (I got a 67mm dia Hoya Cir-Pol for £40, winner!!).

If you take a lot of outdoors pics, and especially landscapes – it’ll be the cheapest improvement you can make to your kit in order to make a huge difference. Mine never come off unless i’m indoors.

Not really.

The reason the sky “blows” is it so much brighter than everything else. So the camera can either give you a nicely exposed sky and a dark foreground or a nicely exposed foreground and a blown out sky. The camera just can’t cope with the range of brightness in the scene.

So what you need to do is darken the sky without darkening the foreground. The traditional tool for this job is a graduated neutral density filter. (There are digital techniques which do the same job as this but results vary from excellent to awful)

A UV filter is mainly just a protective piece of glass you can fit to your lens. It is supposed to cut down on haze a bit but I’m not sure they are worthwhile to be honest. It won’t help your problem at all.

A polarizing filter is not the same as a UV filter. In the context of this question it might actually help sometimes. What it will do is darken the sky a bit – more in some directions, less so in others. This is usually used for artistic reasons and on a bright sunny blue-sky day will probably help a little.

It won’t help on bright cloudy days, or shooting into the sun or other situations where you have a brightness range larger than your camera can capture. Here you need a graduated ND filter or to experiment with HDR.

Cokin drop-in filters are made from plastic, and are not in the same league as glass, for quality. They scratch very easily. They are mainly used to create special effects. Many of which you can now do in Photoshop, tbh.

A UV filter is useful on a Dijical cam, for similar reasons to film cams. The electronic sensors are still sensitive to UV light. Still a useful filter to have.

A polariser is about the only effect you can’t recreate later in Photoshop.

Basically you rotate it on your lens to select which polarised light you want through. It is quite useful for creating blue skies, fluffy clouds etc (though as vinneyh said, an ND Grad filter can also be useful if the problem is the sky is really bright compared to the foreground). It is also useful where you don’t want reflections (say shooting through a window, near water etc).

I like the ability to add a deep blue, vignetted sky like this:

though it can be use more subtly 🙂

http://www.luminous-landscape.com/tutorials/polarizers.shtml

Cokin drop-in filters are made from plastic, and are not in the same league as glass, for quality.

I agree, but since Pete needs an ND filter or two, and won’t be keeping it on the camera all time, it’s the most sensible option for most people.

Peter, why you not have a decent photography guide book?

Good point, but I have STW instead!
😉

OK, so I need a Polarizing filter. Thanks chaps
I just want a simple one on I can put on when I need it. Sets of graduted ones sound like too much faff, TBH.

So maybe a graduated one…
I guess there’s different grades though?

Peter, get a decent book. All you’ll get on here will be people arguing with each other, then it’ll descend into nastiness about Thatcher and Chavs or something… 😯

And polarising filters don’t come in different grades. Spensive ones are betterer than cheap ones. And cheap ones, in that size, aren’t that cheap…

Almost there Peter, ND Grad is a completely separate filter though.
Polarisers don’t have a gradient.

Oh and if you’re buying a polariser then go for a “Circular Polarizer” as a “Linear Polarizer” may confuse the metering system on your camera.

RB – Cheers! I’ll probably get a Hoya one, they’re about £30-£35

Althought to be fair I’m not doing that badly without one. Both of these are straight off the camera. I don’t have (Or really like the effect of) Photoshop.

The second one took some thinking about, and about half a dozen shots until I got that one. To me, it’s perfik. That’s exactly what I was looking at. It’s natural and captures the mood of the day.
🙂

I do have other shots where a filter would heve been useful though

Cheers, Graham. Will do.
🙂

so, I’m lost here. he says that the problem is the sky is blowing out (presumably in comparison to the landscape, else the whole pic is going to be overexposed) on bright days, so people are recommending a polarising filter? Which will probably just turn the sky blue if it’s a clear day?

I’ll probably get a Hoya one, they’re about £30-£35

eBay is your friend!

peterpoddy your sensor is filthy.

Nice pics. Where’s that, Frimley?

Polarisers can make a shot more dramatic. Not always what you want, but can have a good effect:

peterpoddy your sensor is filthy.

How do you know that?

A 400d cleans it’s sensor when you turn it off….

Lens could well be dirty though.
🙂

PP I have used Hoya/Jessop/B+W Clr polarisers over the years and not noticed any real difference tbh.

As RB mentioned, the Cokin range are easy to scratch, the polarisers are glass though I think.

Remember a B+W rep once spouting on about the evenness of the coatings on there filters and how the competition were no way near as good, when we showed him the state of our lens, he soon ran away 😉

Peter – nasty blobs in the sky just above the roof at the left hand side. The sensor cleaning is not magic, unfortunately 🙁

Ahh yes. More likely the lens, though…….

If it is the sensor, can I clean it myself?

highly unlikely to be the lens, the sensor cleaning only removes dust that has not adhered to the sensor filter, i have very similar mark on my shots across all my lenses.

get one of those visible dust ccd cleaning thingies and some bravery and you’ll be fine

the best thing to do is take a picture of blank surface at different focal lengths. if it is the lens then it’ll move

it’s not the lens though

I just want a simple one on I can put on when I need it. Sets of graduted ones sound like too much faff, TBH.

They are however, exactly what you need 😕

A polarizing filter won’t be much help in lots of situations.

It’s not the lens – you wouldn’t see blobs like that from dirt on the lens.

Yes, you can clean it yourself, if you are CAREFUL 🙂 First step is to get a big blower – “Rocket” or similar, and just use that to blow the sensor, following directions from the manufacturer. If that doesn’t work other methods can be tried.

There is a lot of advice about sensor cleaning about on the internet, and it is all given by people who won’t have to pay if you wreck your sensor!!

and as far as grad filters go, use bracketing and/or nikon colour efx pro in PS

be careful with which filters you get – at 17mm you may get some vignetting with non slim fit filters, especially if you use a UV/lens protector AND a polariser

To see the dirt on your sensor: turn off auto-focus, set the aperture to f/11 or f/16, set exposure compensation to +2, take a pic of a sheet of white paper or some other even white surface.

Open the pic up and look at it at 100% – the dirt should be fairly obvious. Try to get rid of the biggest bits.

There should be an option in your camera settings to lock the mirror up. Do that to expose the sensor. Use a rocket blower first to get the loose stuff. Consider PEC pads / Eclipse solution if it is still minging.

and as far as grad filters go, use bracketing and/or nikon colour efx pro in PS

Well, as I’ve already said, it’s a Canon camera and I don’t have or use Photoshop…..

They are however, exactly what you need

No I don’t need them. I carry one camera, one lens attached and will just about have room for a spare battery and a lens cloth when I’ve put a filter in the zipped pouch too. Keep it simple. That’s it. 🙂

If it is the sensor, can I clean it myself?

gt-85 and steel wool

nikon colour efx pro is software so you could use a scanner for all it cares

fair point about PS, give it a go though or try lightroom, the grad ND filter tool in lightroom is brilliant

I think he meant Nik Color Efx Pro – it is a plugin for PS (and also Aperture, I think). Only tangentially related to Nikon.

Another help in looking for dust on the sensor is to apply “auto levels” to your test shot of paper (or sky, or white wall, or whatever)

I’d leave the sensor well alone, unless there’s a significant problem. You could end up **** things up completely. I don’t think a couple of tiny faint blobs are owt to be overly concerned with.

Peter; as for editing/manipulation, consider Photoshop elements. It’s really good at sorting pics out, and is not far off full-fat Photoshop.

Or, try GIMP, which is free, but not as powerful as Elements.

thanks DrJ, I didn’t realise it was ‘Nik’, looking at the licence agreement I realise that now

Or paint.net which is also free and looks more like real photoshop.

More useful reading from Bob Johnson at Earthbound Light:

Do You Really Need a Circular Polarizer?
Essential Filters: Polarizers
Essential Filters: Neutral Density and Graduated ND
A Circular Polarizer Doesn’t Doesn’t Have to be Round, and Vice Versa

Sensor Cleaning: Where Is That Dust Hiding, and What Do I Do About It?

Thaks Graham, some really useful stuff there
🙂

You’re welcome. It’s worth subscribing to his “Photo Tips” RSS feed as he talks a lot of sense and has some useful ideas.