Favour to ask-sample shots at different apertures

dinneenp

Hi
I'm looking for a lens for baby&toddler shots, want good for low light & shallow depth of field. 50mm AF 1.4/1.7 etc or 18-70 or 28-75 2.8 etc. I have a Pentax K-X.
Ideally Id like someone to take sample pics for me:
at each setting from 2.8 up to 1.4 (and one at 4.0 to compare to my kit lens) in a. Lowlight b. Sample of bohek/shallow depth of field.
that way I could judge how much better in low light and how much more bokeh/blurred background nifty fifty/1.4 lens offers over 28-75 2.8 or similar lens and then which to choose.
If anyone could do this Id appreciate it very much.
Thanks,
pa

pixbyjohn

AnCathDubh is your man

Ghost Train

lots of photos here

http://www.pixel-peeper.com/lenses/?lens=1069&perpage=12&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&res=3

http://www.pixel-peeper.com/lenses/?lens=1043&perpage=12&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&res=3

Thecageyone

Aw, they don't have my nifty on that site

Minolta f/1.7

I suppose the closest would be the Sony f/1.8 bar the price tag

Good site for comparison though.

Ghost Train

Ghost Train wrote: »

lots of photos here

http://www.pixel-peeper.com/lenses/?lens=1069&perpage=12&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&res=3

http://www.pixel-peeper.com/lenses/?lens=1043&perpage=12&focal_min=none&focal_max=none&aperture_min=none&aperture_max=none&res=3

I think he wants the same shots over and over again, with the same settings, in the same place, etc. but with the aperture rising in each one (to see the differences from 2.8 to 1.4.

Personally, i think it'd be a useful thing to see also, as I'm wondering myself how "good" a 50mm 1.8 would be and if it'd be worth investing in for this purpose.

Thecageyone

If your not worried about what make or model, just more the difference in aperture range of a general 'nifty', I'll take some shots through the range in the morning on my Sony with Minolta lens. Much of a muchness all of them I'm sure anyhow.

Thecageyone

Thecageyone wrote: »

If your not worried about what make or model, just more the difference in aperture range of a general 'nifty', I'll take some shots through the range in the morning on my Sony with Minolta lens. Much of a muchness all of them I'm sure anyhow.

Well I wouldn't mind seeing it, to be honest.

I'm interested in getting a 50mm 1.8 for my Canon (I wouldn't be able to justify the price of a 1.4) and as all of my lenses at the moment seem to be at 2.8, i'd be genuinely interested to see if this'd make much difference to me.

Chorcai was talking to me before and he seems to think his 50mm is a great lens and uses it a vast majority of the time (dunno if his is 1.8 or 1.4 though) and the 50mm lens seems to be just generally loved by a lot of people that I'm just quite curious at this stage more than anything else.


Apparently it's supposed to be quite useful for low light situations?

Thecageyone

Pretty simple to do a quick demo but more specifics required. The OP doesn't specify what ISO/shutter speed to do the comparison at.

Here's a playful set, first thing to hand, a doll upside-down in a shopping trolley - crappiest tungtsen lighting you can get. All shots 1/25 hand-held, ISO 200 - No processing, just RAW files passed through LR and resized in Ifranview.

f/1.7


f/2


f/2.8


f/3.5


Will do a better comparison tomorrow, was just bored .... and a little tipsy right now

dinneenp

As KKV said, that's exaclty what I'm looking for- I think he wants the same shots over and over again, with the same settings, in the same place, etc. but with the aperture rising in each one (to see the differences from 2.8 to 1.4.) and one at 4.0 to compare to my kit lens

Thanks in advance...

AnCatDubh

i'll give it a whirl with the Pentax FA-50 f1.4 (sorry - but it will be a 'when time permits' effort for me - *might* get to it this evening, if not it would be later in the week). Also have a number of manual 50's at f1.7 - a pentax A and a Rikenon.

On the zoom front, my max'd out aperture on most is relatively poor 3.5 or 4 (the 50-135 f2.8 being on my wish list when I get a grand to spare), except for a manual Tamron which max's out at 2.8. I could use that but it is my least favourite lens of what I own, which I rarely use - it is a heavy beast of a thing and i've just never warmed to it. I must try it again. Also the focal lengths which I would use will be a little rough as being manual the camera won't record some lens related information and iirc the focal lengths is one such piece. Ach, they'd be close enough i suppose depending on how scientific you'd like it.

Having said that, even with the like of the kit lens at f3.5 or f4 you should be able to get some cracking bokeh with the right set of shooting parameters (decent light or steady subject, focal length, distance to subject, and your max aperture of 4 or 3.5).

There's a few more around with the Fa-50's - they may get to it quicker than me - so fire ahead if you do.

Speak a little more about what you are trying to decide between - is it simply a question of is a zoom better for your purposes than a prime, something deeper?

Also, take a look at lenreviews on the pentaxforums. That's where I check before a purchase - mostly every lens under the sun with user reviews.

Finally, if going for the FA50 f1.4, then Kerso (Scotland) I found to be the best value. Obviously do your own checks but i'd suggest to drop Ian an email with a price enquiry.

melekalikimaka

as ACD said, looking at photos isnt quite accurate DOF is dependant just not on size of diaphragm.

Thecageyone

Eurgh ... scientific equations

melekalikimaka

in a nut shell if the dof is say... 10mm, when your 10meters away, go back another 10 meters and dof is halfed... tho i did thus all last year so could be wrong

Thecageyone

Thecageyone wrote: »

Pretty simple to do a quick demo but more specifics required. The OP doesn't specify what ISO/shutter speed to do the comparison at.

Will do a better comparison tomorrow, was just bored .... and a little tipsy right now

Well I obviously can't speak for the OP, but that's very useful to me.

Appreciate you taking the time to do that, Cagey.

Thecageyone

No problem, I was a little drunk when I did it. Surprised they came out in any kind of focus at all

It was done in your average room lighting/tungsten spotlights. You could ramp up the ISO to get better light but that is where the advantages of narrow apertures come in - at f/1.7 - f/2 you can see you'd get away with a faster shutter speed again without having to up the ISO much. Narrower ranges would need an ISO boost, couple of steps, to use any faster shutter speeds. Obviously thes were taken with IS [on the body] on. Not great examples to show the DOF, as there's little difference in that situation/lighting. Whereas bright outdoors you would notice vast changes betwee say, f/1.7 and f/8

AnCatDubh

right, here's the result as they stand - straight from camera;

The constants:

Camera: Pentax K20D
Lens: Pentax FA-50 f1.4
Lens Focal length: 50mm
Mode used: Aperture priority
ISO: 100
Metering: Scene
Focal point in all: Blue peg to the front of the scene
First peg was 6" from the edge of the old bench. Each subsequent peg was 6" from the previous one.

The variables:
Aperture Value as per pdf attachment.
Shutter speed as calculated by the aperture priority mode.
Distance to subject as per pdf attachment (subject being the first blue peg)
To simulate fading light the attachments are taken roughly between 8pm and 8:30pm so light will have varied on the shots and was fading fairly rapidly.

the exifdata.pdf has the tech info which will lead you through the 4 sets of results.

pay attention to the effect of the magical "distance to subject" parameter on depth of field / bokeh.

Thanks to oshead for the exif extractor - always knew it would come in handy and saved me a bunch of time.

If you want any of the original images to pixel peek - just let me know.

If anything my distances to subject are probably quite close, but I hope i've demonstrated that even at f4 you can still control the depth of field by controling the other available shooting parameters.

The apertures profiled here are;
Aperture: f/4
Aperture: f/3.5
Aperture: f/2.8
Aperture: f/2.4
Aperture: f/2
Aperture: f/1.7
Aperture: f/1.4

Setup included tripod mount (not the best tripod in the world but how and ever it was probably more consistent than if I had held by hand).

Shooting was using the K20D's timer function set to 2 seconds.

Think that's the gist of it. (Did I forget anything...... probably).

Thecageyone

Good stuff. Mine just shows how a wider aperture can work better in poor lighting. Out doors, it's more about DOF for sure. And anything below f/4 can be shallow really.

dinneenp

Thanks for the sample pics. Must have taken some time and effort.

Question- I'm looking for lens for pics of toddler & baby so my logic is nifty fifty would suit as good for low light, quick and good bokeh.

But someone mentioned a 28-75 2.8 lens. I know 'everyone' raves about the nifty fifty but how would the 2.8 compare? I'm just thinking that it'd still be good for low light, bokeh, the bonus is that it's got a good range.

Or would you recommend going for the 50?
I have a Pentax K-X.
Cheers,
Pa.
( I promise I won't have tonnes of threads about this).

melekalikimaka

dinneenp wrote: »

But someone mentioned a 28-75 2.8 lens. I know 'everyone' raves about the nifty fifty but how would the 2.8 compare? I'm just thinking that it'd still be good for low light, bokeh, the bonus is that it's got a good range.

Or would you recommend going for the 50?
I have a Pentax K-X.
Cheers,
Pa.
( I promise I won't have tonnes of threads about this).

if its 2.8 all the way through, its a great lens, not a huge difference between 1.8 to 2.8 is a stop... and the extra range imo is worth it, unless your doing serious low light stuff where your struggling with long shutters. also depends in iq of the lens...

dinneenp

melekalikimaka wrote: »

if its 2.8 all the way through, its a great lens,

Yes, it is 2.8 all the way.

charybdis

melekalikimaka wrote: »

as ACD said, looking at photos isnt quite accurate DOF is dependant just not on size of diaphragm.

Are you sure these formulae are correct? They seem to suggest that F number does not influence depth-of-field at all. Also, both equations are defined as "Far limit of depth of field", and surely the depth-of-field is the difference between the two distances and not the sum?

melekalikimaka wrote: »

if its 2.8 all the way through, its a great lens, not a huge difference between 1.8 to 2.8 is a stop... and the extra range imo is worth it, unless your doing serious low light stuff where your struggling with long shutters. also depends in iq of the lens...

The difference between f/1.8 and f/2.8 is 4/3rds of a stop.

melekalikimaka wrote: »

in a nut shell if the dof is say... 10mm, when your 10meters away, go back another 10 meters and dof is halfed... tho i did thus all last year so could be wrong

No, depth-of-field increases as subject distance increases; moving back would increase the depth-of-field.