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zoom lens factors for kit lens upgrade

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rvoller
rvoller  233 forum posts United Kingdom
12 Sep 2011 - 7:54 PM

Hi
I have a Nikon D3100 with standard lense kit 18-55mm. I would like to buy an upgrade, one with further zoom. I would like a Nikkor. Is it true the lower the f number/larger the aperture the better the image quality because more light comes in. And when in use the best image quality is at its largest aperture? or have I got that wrong.
If the specs were the same except weight would a 18-200mm be better than a 50-200mm because it would be more versatile. or would a bigger range have a lower image quality. If I buy a 50-300mm would it have a lower image quality than a 50-200mm.


Thanks
RogerSmile

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saltireblue
saltireblue Site Moderator 43567 forum postssaltireblue vcard Norway23 Constructive Critique Points
12 Sep 2011 - 8:24 PM

As a very general rule of thumb, a zooms image quality starts to suffer when you get beyond 3 focal lengths. That's why they come in flavours like 24-70, 17-55, 17-85, 70-300, 120-300, 150-500[ish] etc etc. There are exceptions but they're fairly few and far between. E.g. a 28-300 is a 10.7x zoom.

(Quoted from a post by MeanGreeny)

paperboy
paperboy  4208 forum posts
12 Sep 2011 - 9:40 PM

AF-S 70-=300 vr is an exceptional lens for the price.....add when able a 35mm 1.8 afs or a 50mm 1.8 afs. Unless you are shooting action or indoor events you probably don't need the very expensive. 2.8 lenses just now.


howard

User_Removed
12 Sep 2011 - 10:35 PM

Roger,

Just a couple of points.

The concept of image quality is a very variable one - or at least different people will consider different parameters and attributes to be important in assessing "image quality". There is another interesting thread running asking if a Leica M9 gives a better "picture quality" than an entry level dSLR at 10% of the price. The answer is "it might but who would know?" Realistically, any decent lens by any of the major manufacturers will provide a perfectly acceptable image quality for most folk who probably only look at their images on a computer monitor or print not any bigger than A3+. Within those constraints, you can really choose any zoom lens by Nikon (or indies like Sigma) that takes your fancy.

In answer to your specific question about aperture - No. A lens will not normally give its best quality images at maximum (i.e. widest) aperture. Most of the lenses that you might consider give their sharpest results in the f/8-f/11 range.

Finally, I would agree that, to supplement your existing lens, a Nikon 70-300mm VR zoom would be a very sensible choice and you would certainly have no problems with image quality from that one.

.

Last Modified By User_Removed at 12 Sep 2011 - 10:36 PM
rvoller
rvoller  233 forum posts United Kingdom
12 Sep 2011 - 11:21 PM

Hi all

Thank you for your help. Since my last post I am leaning towards a 18-200mm as I love natural outdoor photography and wide angle with the addition of zoom for e.g wildlife sounds best choice for me. I hope thats right! Please state if a 70-300mm would be more appropriate for my work which involves landscape. Might be 18-200mm as im only use to my standard 18-55mm.

Yes I have a couple of dslr mags and they state f/8-f/11 have sharpest results. I am getting confused with product description. On the lense for example it states for a 18-200mm f3.5-5.6. Now this f figure must be important but please help me state why. I am noticing the larger the apeture the more expensive the lense. Larger aperture = faster shutter speeds = benefit low light conditions?
On the subject of f, if I took a typical seascape sunset shot I would use the smallest aperture possible to focus the whole depth of field when require?

Thanks for your help

paperboy
paperboy  4208 forum posts
13 Sep 2011 - 12:58 AM

Roger, the 18-200 is a good all purpose lens, but not best for your purpose. If you want wide( quality), you give up long, and viceversa. Your 18-55 is equal to it for landscape. There is no such thing as a perfect lens for zoom and wide, there are varying degrees of OK, for each. You need to decide which type is your priority, Have a read here: lens

User_Removed
13 Sep 2011 - 9:58 AM


Quote: I am getting confused with product description. On the lense for example it states for a 18-200mm f3.5-5.6. Now this f figure must be important but please help me state why.

The aperture stated in the lens description is the maximum aperture for that lens, i.e. the widest aperture it is capable of, when wide open. In the case of cheaper zoom lenses, such as the one you mention, the maximum aperture varies according to the focal length you are using, generally being smaller (i.e. a higher f number) at longer focal lengths. With that 18-200mm lens, the max. aperture at 18mm is f/3.5 but at 200mm it is only f/5.6.

The max aperture is important because it determines the maximum amount of light that can enter the lens when the iris diaphragm is wide open. Remember that there are three parameters that determine your exposure - the shutter speed, the lens aperture and your ISO setting. You may want to fix the shutter speed (e.g. to freeze or blur motion) or you may want to fix aperture (e.g. to determine depth of field) or you may want to fix ISO (e.g. to limit noise).

Like Paperboy, I would question whether you need an 18-200mm lens at this stage as you already have the 18-55mm part of the range covered with your existing lens. The 70-300mm would also give you 50% more "reach" at the long end than the 18-200mm.


.

Last Modified By User_Removed at 13 Sep 2011 - 10:00 AM
JackAllTog
JackAllTog e2 Member 53513 forum postsJackAllTog vcard United Kingdom58 Constructive Critique Points
13 Sep 2011 - 12:53 PM

If you are going for a very big zoom like the 18-200 you could consider the Tamron 18-270 - this guy is road testing one and it seems rather good at the moment.

One big zoom is great, but a simple 50mm f1.8 is also amazing for shaprness and shallow depth of feild.
As time goes on you will probally want less len's but each one should be top quality, and the bigger zooms are not always high enough quality. After primes (e.g. a 50mm), then the better quality 24-70 & the 70-200mm lenses are just great lenses.

p.s. Another massive improvement in shot quality is a sturdy tripod.

rvoller
rvoller  233 forum posts United Kingdom
14 Sep 2011 - 10:46 PM

Thanks all for your expertise. You have made me appreciate I have to be fully certain I buy whats best for my needs. I have yet to use the maximum aperture on my kit lense. I havent done much macro or wildlife. Maybe I will have to buy a wide angle and a zoom for everything else out of reach. I like to remain mobile when out and only settle down when there is a sunrise/sunset to not miss any colour. Digital SLR photography mag recommended a 18-200mm zoom lens for sunsets to be in control of composition. Though I expect any lense with same spec but less zoom increases image quality. I do envy ultra sharp landscape photographs with sunsets/landscapes.
I have my filters but still need to purchase a tripod. I am being fussy which one to buy as I like walking in the outdoors and remain mobile so it is essential the tripod is light quick and durable.

RogerSmile

JackAllTog
JackAllTog e2 Member 53513 forum postsJackAllTog vcard United Kingdom58 Constructive Critique Points
15 Sep 2011 - 12:03 PM

Good tripods are sometimes more worthwhile than good glass for sharpness, carbon fibre are the litest, with aliminum then steel.
But prices here can range from maybe 400 down to 100 for solid tripods. I went for a 100 steel Giotto tripod and ball head. and i can walk for about 3-4 hours with that and a few lenses. but give me a few hundred quid spare and i'd certainly consider carbon fibre.
I'd say good Landscape photographers are usually carrying tripods of some sort. One thing i did not know is that for these more expensive tripods you can buy the head and the tripod seperatly.

As landscape is one of your main interest i'd also take a look at a sigma 10-20mm lens or the nikon equivelent. that extra width can be stunning in landscapes, though you will end up carrying and having to change lenses for more normal shots.
Then comfy bags are essential.

ElSid
ElSid  6 United Kingdom
15 Sep 2011 - 5:16 PM


Quote: I like to remain mobile when out and only settle down when there is a sunrise/sunset to not miss any colour.

Generally I'm the same, I much prefer not to lug a tripod about unless I absolutely know I'm going to use it. The rest of the time I rely on higher ISO and image stabilisation where available.

FWIW I use 18-70mm and 55-300 VRII Nikkors on my D50. At some point I guess I ought to get a 10-20mm type as well but as I only bought the D50 to use my old manual lenses on it's not really a priority. If I want to have extra wide angle capacity then I bring out Canons coupled with a trio of 10-20, 17-70 and 70-200 lenses - sometimes adding a 200-400 to the bag if I'm feeling strong...Grin

There are occasions when I really think it'd be nice to have an 18-200+ zoom just for those times when I don't really want to carry too much but I do remain sceptical about the absolute image quality of superzoom lenses.


Quote: Digital SLR photography mag recommended a 18-200mm zoom lens for sunsets to be in control of composition.

Never come across such a recommendation before though I suppose using one lens rather than having to change form one lens to another it less time consuming. Compostion control though is largely down to bit of thought about what you want to acheive - which should then tell you what focal length you need and where's the best place to stand/sit/lie. Zooms make it too easy to simply zoom in/out without considering whether moving forward or backward and using a shorter/longer focal length lens might ultimately result in a better composition...


Quote: I do envy ultra sharp landscape photographs with sunsets/landscapes.
I have my filters but still need to purchase a tripod. I am being fussy which one to buy as I like walking in the outdoors and remain mobile so it is essential the tripod is light quick and durable.

RogerSmile

Tripods do make a very noticable difference to ultimate sharpness even at shutter speeds where you might think they aren't necessary but they really come into their own when the light is low and or the focal length is long. Light weight is desirable but not at the expense of stability so choose wisely.

LenShepherd
LenShepherd e2 Member 62426 forum postsLenShepherd vcard United Kingdom
16 Sep 2011 - 8:55 AM


Quote: And when in use the best image quality is at its largest aperture? or have I got that wrong.
If the specs were the same except weight would a 18-200mm be better than a 50-200mm because it would be more versatile. or would a bigger range have a lower image quality.

You have got it part wrong.
You are looking at f3.5-f5.6 lenses - all of which perform less than at their best wide open than 2 stops down. Best optical quality is about f8 at the wide end and f11 at the long end - though they are generally good (as distinct from excellent) to f16.
There are several factors apart from zoom range that many regard as important, like build quality, AF speed, distortion and corner shading.
You could improve your photographic potential by substituting the 18-55 for the 18-70 and adding the 70-300 VR - because these 2 lenses are built up to a standard rather than down to a price.
Whilst the 18-200 is marvelous as a "do it all option" optically you are better off with the 2 lenses I suggest.
Whilst your D3100 is a good camera it is not intended for pro use.
Digressing to the f2.8 pro grade zooms zooms I am assuming you do not want to pay this amount of money. None of them are particularly good in the corners at f2.8 but are generally very good from about f4.5 to good at f16 with excellent from about f5.6 to f11 - so many more "very good apertures".
The new f4 16-35 and 24-120 f4 sit somewhere in between - but again put you in a different price league.
One exception to restricted wide open corner quality is the 200-400 at 400mm f4 - but you do not get change out of 4,000 if you buy the current version new.

Sooty_1
Sooty_1 Critique Team 41174 forum posts United Kingdom196 Constructive Critique Points
16 Sep 2011 - 9:14 AM

Tripods are another important bit of photographic kit, just as important as lenses.

You would spend hundreds of pounds on a wide aperture pro lens and then buy a cheap lightweight tripod, or hand hold it, neither of which will stop the camera shake that spoils your pictures in low light? Even with VR (which is only really effective at a limited range of shutter speeds), there is no substitute for solidity.

I would suggest that if the OP is envious of those "ultra sharp landscape photographs with sunsets/landscapes" then he should consider how he is going to immobilise the camera during the exposure. If you are a landscape photographer who likes low-light, then it is just laziness to not use a tripod, and any exceptional shots are probably more down to luck than good working practice. You have to decide what is best - less weight and probably missed opportunities, or flexibility and mobility. Unfortunately, there is no point walking to the best photo opportunity of your life and not being able to take a sharp picture.

I would suggest that an option is to buy an older, secondhand lens (from a reputable dealer) if you want a 70-200 or something long, and use the money saved to buy a good quality tripod and head (for instance, I have a Manfrotto carbon tripod and both pan/tilt head and ball heads. Light enough to carry, stable enough to work).

Nick

rvoller
rvoller  233 forum posts United Kingdom
16 Sep 2011 - 10:47 PM

You all have to give yourself credit for helping a beginner photographer get somewhere the correct way. I dont claim to be a landscape photographer or anything beyond I remain open minded and try to improve myself everytime its just my area of interest.
I only bought my DSLR in August. My budget can only stretch to one item per 1 or 2 months due to the initial high costs involved.
Im starting to understand how I can maximise my potential. 70-300mm would be better than a 18-200 for two reasons. (a) the longer focal length with not have much degraduation in image quality and (b) for landscapes a more specific lense will improve image quality.
The 10-20 sigma has very high reviews worth checking out, though would that mean I would create some akwardness for nothing between 20-70mm? Digital SLR photography mag states the kit lense does not meet the potential of the modern DSLR. The lense is king. Maybe I should consider an 18-70 which I assume out perform the kit lense. The 24-70mm look out of my budget perhaps a second hand one. Im not sure about primes yet maybe one for the future when focal length is second nature.
With the aperture specifications, the bigger the aperture the lower the ISO?
For the tripods I herd the manfrotto neotech was good but thats okay if you can blow 350ish.
I was hoping to purchase a tripod two weekends ago but when I went to a chain camera retail shop the advice was rubbish. They only introduced me to one. lol

Roger

rvoller
rvoller  233 forum posts United Kingdom
27 Sep 2011 - 9:35 PM

Hi everyone
Thanks again for guiding me in which lense to buy for my upgrade. I have now a sigma 10-20mm. Very pleased when opened the box, even more pleased with the shots I took at the weekend.Grin

Roger

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