Prime Lens Questions for a newbie

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GIZTO29

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Philip
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I keep seeing these crop up and have been recommended the 50mm f1.4 by a few people but i cant get my head around not having a zoom. Im new to DSLR as you could probably guess so how do you people use these lenses and what range of things would you use them for? I understand all true macro lenses are primes..... Also after just seeing the 35mm f1.8 thread in this section i was wondering why it was half the price of the 50mm f1.4?
http://www.warehouseexpress.com/buy...kon Fit-_-1028370_Nikon 50mm f1.4 G AF-S Lens
http://www.warehouseexpress.com/buy-nikon-35mm-f1-8-g-af-s-dx-lens/p1030389
Thanks in advance, Phil
 
The 35mm f1.8 on a crop sensor is the equivilent to a 50mm on a full frame camera and is considered a 'normal' focal length. Excellent as a walk around and full/half body portraiture. Having a max aperture of f1.8 makes it ideal for low light too as well as opening up more doors for creativity due to narrow depth of field ability.

The 50mm f1.4 on a crop sensor is great for portrait work but is sometimes to long for everyday photography and especially indoors (it becomes 75mm on a crop sensor). It is more expensive mainly because it has an aperture of f1.4, again even better in low light as it can let in more light!

As for their uses? Primes are held in high regard for their sharpness, whilst in recent times this gap between zooms and primes tightened, primes are still a cost effective way of getting a high quality sharp lens. Primes can also make you think more, being that you cant zoom you have to move around to find the best composition, I personally love using primes for this reason, I find I get more creative with them and they are lighter!

A true Macro lens, be it prime or zoom that has a reproduction ratio of 1:1.

Hope this helps.
 
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Thanks very much for the help. I realised it was due to the aperture but didnt think it would be such a big difference. I have to say i love shots with very short dof.:)
Phil
 
This mornings email not helped then! :D

Remember that dof of feild is also dependant on focal length. you want a telephoto group to really kick off that butiful out of foucs blur. the blur is also dependant on the shape of the aparture blades. roughly speaking the more the better, the 35mm was 7 and the 50mm has nine.

The glass is higher quailty on the 50mm compared with the 50mm, and the 50mm is full frame so there is more glass.

Stuart
 
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Its half the cost because their is less glass in the lens. Less glass means less light hitting the sensor so you get a 1.8 instead of 1.4

They are good lenses for close up things. By close up I mean portraits, not macro. Primes are generally better quality aswell.

Depending on what you shoot it could be a good or bad buy for you. Though its always nice to have a small prime in the bag.
 
The big advantage of primes is that they can do low f/numbers, which is optically very difficult, like f/1.8, f/1.4, even f/1.2. That's about two stops more than any zoom, 4x more light gathering, 8x more than most f/4-ish zooms.

Shallow depth of field is their unique characteristic, and also low light photogtraphy of course - but there are other ways of doing that, like high ISO, image stabilisation, flash.
 
Less glass means less light hitting the sensor???????????????

:thinking:

And it gets me f/1.4

Maybe I should prise the front element off my f/1.8 and go 1.4 for free!?!
 
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As I understand its the otherway round, more glass in f1.4 then f1.8.

Primes are awesome though.
 
If you fancy trying a prime, but aren't sure about it as no zoom, why not get a 50mm F1.8 to have a go with. You can pick them up from Kerso on here for £75 del new or slightly cheaper for a 2nd hand one. If you don't like it, you will easily be able to sell on. If you do like it, you can upgrade to the 1.4 if you wish.

I bought a 1.8 for a lad who was leaving work and he loves it
 
andyred said:
If you fancy trying a prime, but aren't sure about it as no zoom, why not get a 50mm F1.8 to have a go with. You can pick them up from Kerso on here for £75 del new or slightly cheaper for a 2nd hand one. If you don't like it, you will easily be able to sell on. If you do like it, you can upgrade to the 1.4 if you wish.

I bought a 1.8 for a lad who was leaving work and he loves it
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Its £75 for a Cannon lens and the 50mm f1.8 nikon is manual focus on his camera, leraing about narrow depths of feild and manual focus at the same time is a slow road for progress!

Stuart
 
stu_the_flat said:
Its £75 for a Cannon lens and the 50mm f1.8 nikon is manual focus on his camera, leraing about narrow depths of feild and manual focus at the same time is a slow road for progress!

Stuart
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Oops should have read his signature more thoroughly
 
"Remember that dof of feild is also dependant on focal length."

Sorry to be a pain and I know that this is one of my pet subjects but DoF is not dependant on focal length. As we're talking to a relative newbe I think it's worthwhile being accurate (if a bit of a pain.)

Using a longer lens will have the effect of making distant objects larger in the frame and will therefore show any out of focus items to be more obviously out of focus whereas with a wider lens out of focus elements may be smaller in the frame and so less obviously out of focus, indeed they may appear to be in sharper focus as small things can look sharp, but this is all an optical illusion and all else being equal DoF is decided by aperture and format size and not focal length.

Back to topic... for me primes can offer two advantages over zooms... the first is a wider aperture for shallow DoF and low available light shooting and the second, in the case of macro lenses, is closer focusing and possible 1:1.
 
:)

I hope you don't mind me butting in. I just thought that as it's a relative newbe....

I have a technical background and therefore the technical aspects of all this tend to appeal to me and I also spend most of my time using wider lenses, hense the interest in DoF.
 
I find that using a prime improves your skills as you need to think a lot more about composition and framing.
 
woof woof said:
:)

I hope you don't mind me butting in. I just thought that as it's a relative newbe....

I have a technical background and therefore the technical aspects of all this tend to appeal to me and I also spend most of my time using wider lenses, hense the interest in DoF.
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Not at all, I prefer it when people correct me. its one of the ways I learn! :D It was a fact that I was aware of but had pushed to the back of my head. as you point out what i said was wrong.

Stuart
 
woof woof said:
DoF is decided by aperture and format size and not focal length.
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If we're going to b really finickity, we can actually say that DOF isn't affected by format size. It's just that having the same focal length on a different format requires you to move your distance from the subject, which affects DOF. So while format size is an indirect factor in controlling DOF, it does not directly control it. If I slap an 85mm f/1.8 on a crop body, it doesn't automatically deliver more DOF than on a full frame body, just because the sensor behind it is smaller. It's the fact that you have to move back to frame the subject the same, that changes the DOF.
 
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We'll keep each other right and accurate!!!! :)

What I actually had in mind by format size was the resultant print / image size as with bigger images out of focus stuff is easier to see, smaller prints / images can look sharp when in fact they may not be.

I'm actually not too sure about format size as in sensor size as I keep reading that compacts have a lot of DoF. I haven't spent a lot of time checking compact camera DoF so I really can't say.

A subject for test and another thread?
 
I never quite understood why having a diffrent sized sensor changed the depth of feild, as i understood it a sensor "crops" so for the DoF to change that would mean the DOF was not uniform accross the image, which sounds daft!

Stuart
 
Yup. But the compact DoF thing is repeated time after time and it's always phased me a bit, might be worth looking into.

The problem is that by the time I've equalised images they often pixilate and than you can't really see what's in and what's out of the DoF anyway. I might see if I can get some comparable shots over the weekend.
 
stu_the_flat said:
I never quite understood why having a diffrent sized sensor changed the depth of feild, as i understood it a sensor "crops" so for the DoF to change that would mean the DOF was not uniform accross the image, which sounds daft!

Stuart
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Given the same focal lens on a small and a large sensor, you'll have to move further away with the small sensor to capture a similar content. As depth of field is dependent on the distance to the subject, this explains the differences.

Independent of this, you'll probably change to a different focal length for the smaller sensor in the first place. Then the question is whether the perspective effects are similar between the small sensor with short focal length and the large sensor with longer focal length.
 
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stu_the_flat said:
I never quite understood why having a diffrent sized sensor changed the depth of feild, as i understood it a sensor "crops" so for the DoF to change that would mean the DOF was not uniform accross the image, which sounds daft!
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The key to understanding it is that the larger sensor will exhibit a smaller depth of focus for the same field of view (framing).

Try it with this DoF calculator here.

Shooting with a 75mm lens at f/4 on full frame (e.g. Nikon D3x)

Focusing distance 1.0m

= Total DoF: 0.04 m


Now, same lens, same aperture on a D200 with a 1.5x crop, focusing distance 1.0m

= Total DoF: 0.03 m


The crop body has less depth of field? Conventional wisdom is wrong? eh?

No.

Because to get the same FoV as the 75mm on the D3x, you'd have to use a 50mm lens on the D200.

Now, Total DoF at f/4 = 0.09 m



Or you could step back a bit with the 75mm to fit the same stuff in the frame (albeit with a change of perspective)

D200, 75mm lens, f/4, focusing distance 1.5m: total DoF = 0.09 m


Try the same on a 6x9 film camera (0.4x crop factor vs 35mm)

75mm lens, f/4, focusing distance 1.0m: 0.09 m



but again, we have to make allowance for the fact that a 75mm lens on 6x9 will get you the same FoV as a 30mm lens on 35mm film.

So, now we have to use a 190mm lens to get the same FoV as the 75mm on the D3x.

Total DoF = 0.01 m



Or get in closer to 0.4m from the subject: Total DoF = 0.01 m
 
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Practical example: f/4 at about 1m focusing distance with an 80mm lens



Potters Fields by cybertect, on Flickr


However this is on 645 medium format film, so the equivalent of 50mm standard lens on '35mm full frame' digital or a 30mm lens (say the Sigma) on APS-C crop digital.

Try shooting with a 30mm lens on a Canon EOS 500D and you will not get that bokeh at f/4. ;)
 
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Musicman said:
The key to understanding it is that the larger sensor will exhibit a smaller depth of focus for the same field of view (framing).

Try it with this DoF calculator here.

Shooting with a 75mm lens at f/4 on full frame (e.g. Nikon D3x)

Focusing distance 1.0m

= Total DoF: 0.04 m


Now, same lens, same aperture on a D200 with a 1.5x crop, focusing distance 1.0m

= Total DoF: 0.03 m
Click to expand...
And there you have it, the sensor DOES come into the equation to figure out the DoF. All you've done in the above equation is changed the sensor size, yet the DoF HAS changed.

What everyone has so far missed out of their calculations is the (aptly named) circle of confusion. See: http://en.wikipedia.org/wiki/Circle_of_confusion
 
arad85 said:
And there you have it, the sensor DOES come into the equation to figure out the DoF. All you've done in the above equation is changed the sensor size, yet the DoF HAS changed.

What everyone has so far missed out of their calculations is the (aptly named) circle of confusion. See: http://en.wikipedia.org/wiki/Circle_of_confusion
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Well, yes.

Because DoF calculators assume you're printing onto a standard 8x12 sheet and the crop body image is being enlarged more than the full frame one - the tolerances are tighter.

The calculator I linked to takes that into account by adjusting the circle of confusion size for each format, which is shown at the bottom of the results panel on the right.
 
Sparked a very interesting healthy conversation. ;)
 
Depth of field is determined by just two factors - image size (magnification) and f/number. Two situations:

1) A crop format camera records a smaller image than full frame, so you have to use a 'smaller' focal length to squeeze the same field of view on to it. For example, shooting side by side with a full frame camera and 50mm lens, the guy with a crop camera (Canon) needs a lens 1.6x shorter to get the same field of view, ie 31mm. In terms of framing and perspective, the images are identical, but the crop camera and shorter lens is delivering more depth of field. The difference is f/number x crop factor, ie about one and a quarter stops.

2) If you are shooting a portait at say 4ft with a 50mm lens, then change to 100mm but move back to 8ft, the depth of field will be the same, because the subject remains the same size (same magnification). Note however that here the perspective changes and that the narrower field of view with the longer lens shows less background behind the subject. It looks less cluttered and distracting, with 'bigger bokeh' which often creates an impression of greater subject isolation that looks a bit like shallower depth of field, even though it is not.

Comapcts do indeed deliver greater depth of field, because their sensors are so small. Compact fomats vary but a crop factor or 5x is typical. Which means that, relative to full frame, f/4 on a compact delivers the same depth of field as f/20 on full frame :eek: At normal shooting distance, it is impossible to get creative depth of field effects with a compact - pretty much everything is sharp, whether you like it or not.

Check it all out at www.dofmaster.com
 
Next time I go out I'll take my APS-C DSLR, my GF1 and a comapct and I'll shoot everything three times. I'll then sit and look at them on my pc. That's my weekend sorted!
 
woof woof said:
Next time I go out I'll take my APS-C DSLR, my GF1 and a comapct and I'll shoot everything three times. I'll then sit and look at them on my pc. That's my weekend sorted!
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For same DoF, same viewpoint and framing and focusing position, say f/4 on the compact (assuming 5x crop factor), will be the same as f/13.3 on a Nikon cropper (1.5x), or f/12.3 on a Canon (1.6x) or f/10 on the GF1 (Micro 4/3rds, 2x).

Better shoot something close-ish ;)
 
stu_the_flat said:
I wonder if GIZTO29 is still reading this? :D
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Im trying honest! :eek: Its went way over my head i have to say:lol: RE your op Stu i dont get to read my PMs till night after work usually and the 5 PM thing on AO is pathetic!
Now where was i up to......:lol:
Phil
 
just look the price of a digital meduim format camera, then I suspect you will file it in the "not really relavent until I win the lottery" section of your head!

Still an interesting read though

Stuart
 
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"For same DoF, same viewpoint and framing and focusing position, say f/4..."

To see the effect of different sensor sizes, if there is an effect, I'll take the same shot at the same aperture on a 20D, GF1 and LX2. I'll frame the shots to be a close as possible to each other.
 
stu_the_flat said:
just look the price of a digital meduim format camera, then I suspect you will file it in the "not really relavent until I win the lottery" section of your head!
Click to expand...

If you have a £25 to spare, you can buy a working 120 folding film camera though. ;)
 
HoppyUK said:
Depth of field is determined by just two factors - image size (magnification) and f/number. Two situations:

1) A crop format camera records a smaller image than full frame, so you have to use a 'smaller' focal length to squeeze the same field of view on to it. For example, shooting side by side with a full frame camera and 50mm lens, the guy with a crop camera (Canon) needs a lens 1.6x shorter to get the same field of view, ie 31mm. In terms of framing and perspective, the images are identical, but the crop camera and shorter lens is delivering more depth of field. The difference is f/number x crop factor, ie about one and a quarter stops.

2) If you are shooting a portait at say 4ft with a 50mm lens, then change to 100mm but move back to 8ft, the depth of field will be the same, because the subject remains the same size (same magnification). Note however that here the perspective changes and that the narrower field of view with the longer lens shows less background behind the subject. It looks less cluttered and distracting, with 'bigger bokeh' which often creates an impression of greater subject isolation that looks a bit like shallower depth of field, even though it is not.

Comapcts do indeed deliver greater depth of field, because their sensors are so small. Compact fomats vary but a crop factor or 5x is typical. Which means that, relative to full frame, f/4 on a compact delivers the same depth of field as f/20 on full frame :eek: At normal shooting distance, it is impossible to get creative depth of field effects with a compact - pretty much everything is sharp, whether you like it or not.

Check it all out at www.dofmaster.com
Click to expand...

Gad sir, you sure love DOF Master :D
 
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