Camera lenses..

[imamartian]

(not sure which category to put this in really)...

But anyway, what a minefield. I have a fairly decent canon camera with the kit lens (18 - 55mm).

Now i want the next lens up.. i'm assuming something like a 70 - 300mm telephoto. But the choice is mindboggling wide. And the prices the same.
It seems you can pay anything from £150 - £8000 for this lens. And if you look at the specs, they seem very similar.

What are the key things i'm looking for? what is the difference between the top end and the bottom, is it just the quality of the glass? or would i get a better zoom etc?

 

[ChrisFrost]

Not an exhaustive list, but...
The quality of the glass and the grinding precision.
More light throughput (F-stop)
greater depth of field
Less colour shift (chromatic aberration)
sharper focus across the entire lens zoom range
even and sharp focus at the edges of the picture
Coatings on the lenses to help reduce lens flair


Quality costs money. Precision grinding and optics demonstrate that quite clearly. Go have a mooch on some of the photography forums and see some images shot on different quality lenses.

 

[ericmark]

I went for cheap option. Second hand full format lens. With my Pentax this also means no electric connection but a 85 - 210 mm (35 mm rating) cost me £35.
My sister paid around the £1000 for a 18 mm to 300 mm for her Nikon full automation.
So in real terms what is the difference.
1) I have to change my lens which means dust can get in.
2) To stop down I have to either set camera to over expose or use manual.
3) Focus on mine pure manual.
If I was taking pictures of birds then my sisters camera would run rings around me. The problem with my lens is the time it takes to set up and focus and following birds or sport you just have not got the time to do this.

But pictures where I am a little further away than I can crop pictures and keep some reasonable resolution will come out as good with my old lens as with my sisters expensive one.

Lens quality will of course change with the more you pay. But it is more on the wide angle with the distortion where this is scene than with telephoto.

However even with 1600 ISO I do find with my cheap lens the aperture is not really wide enough to hand hold in anything but bright sun light. The more you pay the wider the aperture. Also with CAT lens they are much shorter. Using fixed length lens and manual you can get a lens like this which is super cheap and very long and they will work. But again manual. Remember with a cropped CCD this lens is more 800mm.

So question has to be.
1) What do you want the lens for.
2) How deep is your pocket
3) How well do you understand your camera could you use it in manual.

My Pentax unlike the Canon and Nikon still can use the same lens today as they did in 1978 it will just clip on. OK I lose the electronics but I do still have a focus aid which flashes a red spot when correct. Remember auto focus on a Pentax is in camera not lens. So lenses for Pentax don't cost as much anyway but are slower to focus.

In hind sight I would have likely been better with a compact with a good lens and RAW which would have cost between £300 and £500 and would have not had the dust problem plus non SLR's can normally take movies.

The SLR can't take moving pictures as the mirror would not allow one to see what one is taking. Some modern ones will allow one to use them in compact mode. And use CCD and LCD to view what you are taking.

But although I have a 85 - 210 and a 400mm fixed I find the haze does not allow one to take distance scenes good enough to really use the photos. It would not matter what lens you have.

A zoom lens can be mounted backward and then the zoom control becomes focus for taking real close up. But unless you do that the cheaper lens will not allow you to be close. My 400mm lens starts at 20 foot so again what do you want to do with it?

 

[imamartian]

looking at the spec of these lenses...am i looking for the biggest depth of field? and what does MM (maximum magnifiction) mean? i'm seeing values of 0.2X
i thought telephotos were zoom lenses?????? my bridge camera has 18X

 

[ericmark]

OK I will try to explain.

Zoom means the focal length is not fixed and the same lens has a range of focal lengths. The standard lens with my camera was 18mm to 55mm.

Focal length. This is the distance from CCD or film plane to the theoretical cross over point of the image. The problem is the larger the CCD or film the larger the focal length in order to capture the same image. So one can compare between cameras this is often given as a 35mm equivalent length. So with my camera a picture opened up in "Bridge" will report in the meta data a focal length of 20.0 mm but also show Focal Length in 35mm Film of 30.0mm to help compare.

The (Something)X figure and the focal length range do give the same information but one needs geometry to work it out. So 18 - 55mm will give a 9.3 times zoom. This I worked out by considering the area captured 1 meter from camera with a 23.5 x 15.7 CCD with an 18mm lens this is 1.13 sq meters and with a 55mm lens is 0.12 sq meters so divide one with other gives X factor of zoom. So 85mm to 210mm = 6X zoom. 18mm to 210mm = 136X zoom. Hence the massive figures one sees on a cine camera. The cine camera combines optical and digital zoom together hence the huge figures like 800X. So 20X zoom could be 18mm - 80mm or 50mm - 225mm it only says difference it does not show how much area captured. It's the power of large figure divided by power of small figure not just large divided by small.

In the same way some cameras show the magnification compared with a standard lens for a 35mm camera considered around 50mm but because there is no exact standard lens to compare with it only really works for add on lenses where for example you fit a fish eye adaptor onto the filter screw on existing lens.

The word "Bridge" has a few meanings. Often it means you can print direct to printer without needing a computer. But it is also the name of the Photoshop program which allows you to view and organise photos even in RAW format and select which to load into the main program.

Depth of field is normally variable except with CAT lenses. It is controlled by the aperture. You have three variables when you take a picture.
Speed
Aperture
ISO (Was called ASA or DIN with film cameras)
When you take a picture you or the automatic bit of the camera has to balance out the three options with the light available to get the best result.
The ISO will normally start at around 100 and could be as high as 132,000 and the higher the setting the more noise (same as grain with film) you get. So with my camera set at 1600 ISO if I try to lighten the dark areas I will get the speckle effect and spiting of colours. But at 100 ISO I can apply fill light without a problem.
If we consider mid range of 400 ISO and then look at speed v aperture then set at f32 and 6 seconds my depth of field would be massive however likely it will also show every speck of dust on lens and CCD plus at 6 seconds would need to be on a tripod. As one goes to around f8 which is for most work the smallest aperture one would want to select the speed of the shutter increases so under same light conditions to around 1/4 second still needing a tripod. At around f2 in same light conditions then looking at 1/20 second at which with a floating CCD which reduces the effect of camera shake you may get away with hand held.

So it's a trade off and you can select the depth of field. It's not really something fixed to the lens except with CAT lenses where the mirrors used often means fixed aperture.

There are software fixes for depth of field either using stacking or layers and mask so you can take a series of images at different focal lengths and combine them together either auto or manual.

Nearly every image I take will be corrected in some way with photoshop. All start as RAW images so they have to be converted with software to be able to get printed so they are all loaded into some software package. So the "as taken by camera" just does not come into the argument as we can't use the pictures "as taken by camera". It does not really matter if converted to Jpeg in camera, or with computer software, it is converted somewhere. In the same was as film was developed, and printed, and the developing, and printing could make or break the final image.

This means like the cine camera we can crop the image and so effectively zoom in. My monitor will display 1280 x 1024 pixels which will need about 1 Meg. So I can crop a 10M image to 1/10 of it's original size and still not lose definition as that is limited by my monitor. Do remember if you reduce height and width both by half that's 1/4 of original not 1/2. So you with a 10M image can show 1/4 of original hight and width without any degrade to image viewed on monitor.

So combine the lens zoom 18mm to 55mm = 9.3X plus digital of around 10X that gives a total zoom of 90X without loss of viewed quality. By reducing the display quality one can just like the cine have a 300X zoom.

The printers can have a far higher quality than the monitor. Typical 300 dpi but again it depends on size you print at. A 12 x 18 picture does need to be spot on. However a 4 x 6 will not show the faults in the same way.

From what you say as yet you have not learnt how to use the camera and although one can take good photos with cameras set to auto on all functions once one starts using long lenses then one has to understand the camera a lot more. So I would try using the camera in manual. Still use the built in meters to get right exposure but play with high speed v small aperture and see what it does.

The Nikon has a series of options for many of the common situations so even in fully auto mode you can bias the camera to better depth of field or better freezing of motion. Personally I would never use these toys and prefer the more down to earth options offered with the Pentax like Speed and Aperture priority where you set speed and aperture and the camera selects the ISO to suit. Each make has plus and minus and as you say both for camera and lens there is really no limit to what one can have. I was looking on Monday at the GPS fitted to Pentax so it records not only where taken but the direction and can even compensate for camera not being level. In fact on long exposures it can follow earth's movement. Where will it all end?

 

[imamartian]

Wow!!! Thank-you so much for taking the time to answer my questions so comprehensively.

You're right, it's that long ago i was using disposable cameras, i'd take them in to be developed and buy another one.
The digital era for photography seems to have taken off so quickly.
In the past couple of years, i've bought a number of compact digital cameras, but used solely on IA. So the main consideration has always been how much zoom it's got.

I have recently treated myself to a Canon 60D. And decided it's time i learnt how to use it properly... I typically use it on Apperture priority, and take varying shots trying to adjust the depth of field of things like portraits, walks, nature etc. I have also experimented with Shutter priority and taken pics of the kids cycling past, or running water etc.

I nnow find i need to adjust the ISO as the pics suddenly get a lot darker.

So my new lens will need to be in the region of 70 - 300mm. But i have a lot more research to do yet, and also re-reading your response again a few times to try and digest it.

Thanks again.

 

[ericmark]

Not a Canon man but the 60D is a nice camera. With ISO of 6400 on manual and 3200 in auto mode it will allow you both good depth of field and movement freezing and the amount of pixels will also allow some good cropping or digital zoom.

With rapid shooting you may have to use Jpeg so the camera does not stall while writing to SD card, but other than that one really should use the RAW mode. That way you can select the sharpness, colour, and enhance any dark areas at your leisure rather than trying to do it all during the exposure.

I have been surprised when working inside a local wood on how low the light can get and have realised how important the tripod still is. I have an old expensive tripod but it's heavy and takes some time to screw the camera to it. So now use a lighter Lidi tripod Aldi also did same both less then £20 and this has transformed my work as it allows you to do so much more. Multi-images as panorama, focus stack, and HDR stack have to be practised before at the time of shoot one can really judge what is required and what will work. The smart multi image to remove people I found rather a failure although CS5 may do a better job. Also not too keen on CS4 with auto HDR. Picturenaut seems better can't afford Photomatix which it seems is best.

I have a 85 - 210mm and a 400mm lens the 400mm total manual (Pre-set) is for most things too much and although it will bring in distance scenes the haze normally means they don't make a good photo so the 85 - 210mm is the lens I use most to capture distance shots.

Wild life and sport move so fast again to use the 400mm is very hard to capture this is not helped by having to manually set the distance. So with wild life and sport a long lens needs a fast auto focus and wide aperture so needs a lot of skill to use both working out where to place oneself to get the shot and panning technique.

Although I did an A level in digital photography it was the local camera club which helped my most. Guest speakers and competitions where the judges tell you why they selected the photos can really open ones eyes. Competition photos are not the same as good photography where over exposure is always considered bad but look at images used to advertise and often they are over exposed to give effect wanted. One gets use to people telling one to dodge and burn although since I correct in the RAW mode I don't use those tools.

May seem odd but I use shutter priority to get maximum depth of field. What I do is work out the minimum speed I can hand hold the lens in use and set that so camera then auto sets aperture to match giving smallest aperture that I could use.

Same applies to moving subjects. Set aperture to wide open will mean the camera will use fastest speed it can for given light.

If of course you want the blur the process is reversed. This

example (If face book is not banned on your PC) shows an experiment with low shutter speed and panning. Taken at 1/15 second it goes against the rules for moving items and shows the problem where because I was pivoting around a spot the speed of the truck relative to me varied over the length of the truck. Hence everything but cab is blurred. Taken during my A level goodness knows what motorists thought with a pavement of 20 people all taking photos of them as they passed!

Anyway good luck. I am sure you will find it a captivating hobby.

 

[imamartian]

Firstly i wish you were my next door neighbour !!

and secondly, that lorry pic is bizarre !!

I intend to join a club.... and learn the basics properly first.

What are your thoughts on bridge cameras? i have a Panasonic DMC FZ18 which has 18X optical zoom (and 4X digital)... and gets a lot of use.... lovely piece of kit.

 

[ericmark]

If I was starting again I would look at something like the Fugi Finepix F550 as with a 15x optical zoom (equivalent to 24-360mm on a 35mm camera) and RAW capability and with fixed lens no dust problem likely this would out preform my D-SLR.
Although only F4.4 the ISO of 12800 that's not a problem. The only real problem is the shutter speed of 8s is much higher than my D-SLR which will go to 30s after that stop watch is good enough. But with the auto HDR and other features what one loses on the swings one gains on the roundabouts.

I think there is a similar Panasonic in the LUMIX range and one has to ask oneself is the day of the SLR over. Many SLR's now have the ability to disable the very bits that make it an SLR. i.e. the reflex mirror. So even SLR's are now often used in non SLR mode. The 4/3 cameras still have interchangeable lenses but by removing the mirror have become much more compact.

People still use the large format cameras and also still use film so the SLR will likely remain as a cheap (Yes cheap try looking at top end twin lens cameras) method of taking the picture where film is used. But with digital in the future I can see their decline and the 4/3 or similar taking over. The closer one can put the CCD to the lens the smaller the diameter of the lens so they become cheaper and lighter without loss of quality so yes the days of the D-SLR are numbered.

 

[ChrisR]

try looking at top end twin lens cameras

They don't make THOSE any more, apart from for some weird phtographers! I've still got one, somewhere.

Larg(ish) sensors will be with us for a long time, it's down to the laws of physics and how greedy people get/remain for image quality.
As I'm sure you know light comes in packets called photons. If you can only grab a few of the ones you actually want on your pixel, the random noise in the system gets in the way. The human eye is , surprisingly, able to detect a single photon of light, which amazed me, I thought there would be huge numbers of them.
So cameras with larger pixels work much better in low light, and phone cameras by comparison are awful. They're getting better, but there is a limit.
That's why Apple don't put 14MP sensors on their iPhone - they know the chip's too small and don't pander to people who don't.

So if ,eg, you want a fast shutter speed, you want a big sensor, and so on. There's lots of "Ah yes but"s, which take quite a bit of learning to understand, you tend to win on one thing as you lose on another. Ultimately you have more flexibility with a bigger sensor.

Look at what the pros are using though, currently in studios up around 50MP on big sensors, and out for sports etc, still mostly on 24 x 36mm.
Top landscapers are still using plate cameras and film, because , yes, it's better for what they need. I used to use those, and it's lurvly. It's true that you can do well with digital though and combine a few, or a few hundred images and get things which would have been impossible a few years ago.

Apart from compacts I have an 18MP on APS-C and a 12 MP on 24 x 36. I used the latter recently in a wedding reception disco, at night, lit only by coloured disco lights, of people dancing. They thought I couldn't be possibly be taking pictures . It does weigh and cost about ten or twenty times as much as my 10:1 Lumix, though.

I expect for normal sensible people, something like micro 4/3rds sensor size will get really good. At the moment though there's a peculiar bunch of cameras which use it. I'm an old groat who still wants to look thgough an actual viewfinder - which counts most of them out!

That camera ericmarc points to is amazing value - about 3 tanks of gas for heavens sake. The next step up would be something like a Lumix DMC-G2, but you're starting to get much bigger lenses, especially if you want a long telephoto.