Is a fast lens as important today as 30 years ago?

I actually meant those that insist on a very wide DOF, preferably infinite (with wide lenses etc.) trying to get sharpness all the way true the image...

Good points on the modern noise issues.

-----------------------------------------------
Georg Peranen
http://koti.welho.com/wel00296/

liquid stereo said:

The 100/2.0 is the only lens I really want.
I wish I could find one for sale somewhere.

Cheers!

Click to expand...

I have one I bought new twenty-one years ago and it's in excellent condition. I'm waiting for the Flagship model. If it turns out to be a bomb, meaning not FF and/or any better than my Canon 5D, I will give up on Minolta/Sony after 44 years. I will sell off all of M/S stuff and go with Canon only. You can click on my name above to see what I have.

Jerry

Dang... you have a lot of lenses.

I would love to have a bigger collection, especially of those primes...

but how do you decide which lens you want to shoot with? You have overlap there, and plenty of "similar" ranges... what is your thought process?

Because of budget issues, I only have four lenses. It makes it incredibly easy to pick, do I want wide angle, normal, or telephoto? (50mm is a specialty lens, going by that thought process)

I don't even know what I would do with that many great lenses.
--
Gear:
A700, 5D, 50 f/1.7, Sigma 10-20, Tamron 28-75, Beercan, 3600

On the other hand... Why crank up the ISO to 800 or 1600, if you have lenses that work at ISO 50, 100, 200, or 400 in a wide variety of light conditions?

If I could afford it, all my lenses would be F/2.8 or faster. How big would a 50-500 have to be at constant F/2.8? 140mm front element? 30 lbs. give or take?

ck3 said:

Just to clarify: AFAIK a 135mm at 2.8 gives the same DOF regardless
of sensor size.

Click to expand...

Nope, it does not.

See any decent depth of field calculator, e.g. http://www.dpreview.com/learn/?/Glossary/Optical/Depth_of_Field_01.htm

Select a 135mm aperture, F2.8, set any distance, and choose your sensor size. Press Calculate, and it will produce a set of figures for you, indicating the depth of field that the given circumstances will produce. Now change sensor size, and press Calculate again. The figures change.
--
Stuart / the Two Truths
http://www.flickr.com/photos/two_truths/
http://two-truths.deviantart.com/gallery/

I got all of those lenses from 1985-1997. At the time I was photographing for weddings, newspapers, magazines and high school yearbooks. Each lens had it's own purpose, depending on the type of work I was doing. There were others, 28mm F2.8, 35mm F2, Beercan, 135 F2.8, Tokina 80-200 F2.8, 35-200 F3.5, and a couple Sigma zooms along with Maxxum 700, 500, 700i and two 9000 bodies that were sold over the years.

All the lenses are waiting for the Flagship, I hope it's worth it.

Jerry

Cyrus84 said:

Dang... you have a lot of lenses.

I would love to have a bigger collection, especially of those primes...

but how do you decide which lens you want to shoot with? You have
overlap there, and plenty of "similar" ranges... what is your thought
process?

Because of budget issues, I only have four lenses. It makes it
incredibly easy to pick, do I want wide angle, normal, or telephoto?
(50mm is a specialty lens, going by that thought process)

I don't even know what I would do with that many great lenses.
--
Gear:
A700, 5D, 50 f/1.7, Sigma 10-20, Tamron 28-75, Beercan, 3600

Click to expand...

85mm 2.8 1/60 800 ASA 7D



Regards,

Things haven't changed much. Fast lenses have their place.

for sharpness. Very few lenses are sharpest wide open, so you stop it down at least one stop for better images. That makes an f2.8 lens an f4.0 real quick. Then too, f2.8 lenses are better at resolving than slower lenses. Something to do with the physics of optics I believe. Also, remember since the invention of the "auto diaphragm" over a half century ago, a faster lens means a brighter viewfinder image. I always prefer at least an f2.8 lens for these reasons. Just wish I could always afford them!
--
G. Lassman

Papasha said:

If (and only if) your girlfriend is more valuable for you than a G
lens in you hands, try locating 100/2.0 - it should not be that
expensive, but is extremely sharp even wide open and will create
unbelievable bokeh.

Click to expand...

That is still one of the big problems with Sony. They don't make this lens so you have to scrounge around and try to find a used Minolta one. May not be easy to do either. Canon has a 100mm f2 and 85mm f1.8 and they are both pretty reasonably priced. You can buy them anywhere (B&H, Amazon, Adorama, etc.) or easily get a used one right this minute if you want. No searching, no hoping, no waiting. I suppose Sony will someday fill out their lens line, but until then it means trying to get buy finding used lenses.

--
Henry Richardson
http://www.bakubo.com

Henry Richardson said:

Papasha said:

If (and only if) your girlfriend is more valuable for you than a G
lens in you hands, try locating 100/2.0 - it should not be that
expensive, but is extremely sharp even wide open and will create
unbelievable bokeh.

Click to expand...

That is still one of the big problems with Sony. They don't make
this lens so you have to scrounge around and try to find a used
Minolta one. May not be easy to do either. Canon has a 100mm f2 and
85mm f1.8 and they are both pretty reasonably priced. You can buy
them anywhere (B&H, Amazon, Adorama, etc.) or easily get a used one
right this minute if you want. No searching, no hoping, no waiting.
I suppose Sony will someday fill out their lens line, but until then
it means trying to get buy finding used lenses.

--
Henry Richardson
http://www.bakubo.com

Click to expand...

I kind of think that Sony has been very good about continuing to increase its lens lineup.

They started with a lot, and they've been rolling out even more. The only problem, for my budget at least, is they are rolling out more expensive lenses than I can afford.

--
Gear:
A700, 5D, 50 f/1.7, Sigma 10-20, Tamron 28-75, Beercan, 3600

Remember that DOF is based on perception -- What is the largest Circle of Confusion that will appear sharp in the photo when viewed in its final form?

The sizes of the CoC (with distance away from the focus point) on the sensor (film or electronic) resulting from a 135mm lens focused at a given distance and aperture is independent of the format size. But since a small format image requires greater enlargement to be the same size as an image from a larger sensor, the CoC on the final image will also be larger than that from the large format image, resulting in less DOF.

But there are further real world complications. Since the FOV is smaller for the small format sensor, a small format photographer wanting to capture the same image as his large format brother (w/o any post process cropping) will have to either be further away from the subject (and keep the same FL lens, but change perspective) or use a smaller FL lens (and stand in the same position and keep the same perspective). Both of those conditions will increase the DOF of the small format image.

The DOF changes linearly with the enlargement, but with the square of the Focal Length. So changing the lens can greatly change the DOF. However, the acutal amounts of increases and decreases can get confusing depending on the combination of parameters. For example a P&S camera with a very small sensor, may use such a small FL lens that the subject is further than its hyperfocal distance (HFD), which will result in very deep DOF. Whereas with a FF DSLR the subject may be much closer than the HFD because of the longer FL lens required resulting in a relatively shallower DOF. An APS-C could have less DOF than expected (but still more than than the FF) if the FLs being used put the subject inside of the HFD or much more if the subject is a little further away and is at or beyond the HFD. Because of all of the different conditions possible, particularly if you use different format cameras, a calculator is very helpful.

Tom

Tom,

Great explanation. And another point that I don't think you touched on...(It's a confusing technical issue, so you may have and I missed it)...

DOF is the same for any focal length lens focused and framed similarly (50mm lens at 5 feet, 100mm lens at 10 feet, etc.). But the longer lens will magnify the OOF elements behind the subject and make them look more blurry. Something 5 feet behind the subject in the first example is twice as far away and will look smaller than the same object in the second example which is only 50% furthur away.

Likewise, in the opposite manner, OOF focus elements in front of the subject will be magnified with the shorter lens.

A good example:
http://www.luminous-landscape.com/tutorials/dof2.shtml

Greg

Gregory King said:

Tom,

Great explanation. And another point that I don't think you touched
on...(It's a confusing technical issue, so you may have and I missed
it)...

DOF is the same for any focal length lens focused and framed
similarly (50mm lens at 5 feet, 100mm lens at 10 feet, etc.). But
the longer lens will magnify the OOF elements behind the subject and
make them look more blurry. Something 5 feet behind the subject in
the first example is twice as far away and will look smaller than the
same object in the second example which is only 50% furthur away.

Likewise, in the opposite manner, OOF focus elements in front of the
subject will be magnified with the shorter lens.

A good example:
http://www.luminous-landscape.com/tutorials/dof2.shtml

Greg

Click to expand...

I like the example, but it doesn't explain one thing--

As you go closer and closer, the DOF immediately behind the gremlin starts to come into focus.

So no, the tower will never be in focus, because the difference between 3 feet and a mile is too large for the DOF to cover. But if you notice on the last two images, the pavement behind the gremlin start to come into focus.

So, it depends on what you consider DOF. If I am shooting a portrait of someone, and I focus on the near side of their face, all else being equal, the more "wide angle" lens will have great DOF, bringing the far side of her face more into focus.

I think it is a good example of showing how the different lenses behave, but not a perfect example of DOF-- infinite stays infinite, but the range of sharpness is increased.

--
Gear:
A700, 5D, 50 f/1.7, Sigma 10-20, Tamron 28-75, Beercan, 3600

Cyrus84 said:

I like the example, but it doesn't explain one thing--

As you go closer and closer, the DOF immediately behind the gremlin
starts to come into focus.

So no, the tower will never be in focus, because the difference
between 3 feet and a mile is too large for the DOF to cover. But if
you notice on the last two images, the pavement behind the gremlin
start to come into focus.

Click to expand...

See, that's just it. I don't think it is. You're seeing asphalt that is closer to the gremlin in the wider shot. That same spot is not visible at all in the more tele shot. So the DOF isn't changing, but the wider lens APPEARS to have more DOF since you see items that are less out-of-focus and less magnified.

Cyrus84 said:

So, it depends on what you consider DOF. If I am shooting a portrait
of someone, and I focus on the near side of their face, all else
being equal, the more "wide angle" lens will have great DOF, bringing
the far side of her face more into focus.

Click to expand...

Well, the wide lens will also make the far side of the face seem furthur away, thus magnifying less how out-of-focus it is.

So yes, I think we are both comparing the concepts of "absolute" DOF and "relative or apparent" DOF which is a function of how blurry things appear as you progress away from that zone of focus. The wider lenses are less noticeable with this effect.

Greg

Here is what I was taught over 40 years ago. Take four lenses, 50mm, 100mm, 200mm and 400mm, all have a diameter of 25mm. All of the lenses are focused to 10 meters. The result is all the lenses have the same DOF.

So to sum it up, all lenses, no matter what the FL is and all having the same lens diameter, focused for the same distance, have the same DOF.

Jerry

nm66photog said:

Here is what I was taught over 40 years ago. Take four lenses, 50mm,
100mm, 200mm and 400mm, all have a diameter of 25mm. All of the
lenses are focused to 10 meters. The result is all the lenses have
the same DOF.

So to sum it up, all lenses, no matter what the FL is and all having
the same lens diameter, focused for the same distance, have the same
DOF.

Jerry

Click to expand...

Except that no one I know of today uses "lens diameter" as a criterion. You are talking about APERTURE diameter I think, and even then, we use the f number which describes the ratio.

So you are talking about a 50mm f/2, a 100mm f/4, a 200mm f/8, and a 400mm f/16?

And focusing them all to the same distance would produce radically different framing of your subject, so you'd tend to back up with the longer lenses to get any kind of equivalence, and then the math changes again.

So I find the "same DOF for the SAME F-STOP using the same SUBJECT SIZE" to be a better rule-of-thumb. You gain DOF by backing up, but lose it again by going to the larger absolute aperture diameter.

Greg

I think the general idea, applicable to many aspects of photography in the digital age, is that of what your goal is. Are you out to accomplish what used to be accomplished with film SLRs in a cheaper/smaller set-up - or do you simply want to achieve faster/sharper/quicker performance in your SLR. And depending on your goal, the utility/cost ratio is different.

More light is more light, larger sensors are larger sensors - that doesn't change. But technology has allowed cameras to achieve greater performance with less and less.

A few interesting examples in my mind:

studio photoshoots: get a huge sensor, FF or medium format - max out the megapixels and have a big lens

wedding/low-light photo: high-iso performance and larger lenses (but not too large)

safari: good image quality and huge range competing with eachother, but also mobility and size of lenses matter - this is where a sensor size trade-off might lead to 4/3

spy: small, great range - but does the sensor need to be big? get the secret agent a 1000mm equivalent on a little P/S sensor.

Gregory King said:

nm66photog said:

Here is what I was taught over 40 years ago. Take four lenses, 50mm,
100mm, 200mm and 400mm, all have a diameter of 25mm. All of the
lenses are focused to 10 meters. The result is all the lenses have
the same DOF.

So to sum it up, all lenses, no matter what the FL is and all having
the same lens diameter, focused for the same distance, have the same
DOF.

Jerry

Click to expand...

Except that no one I know of today uses "lens diameter" as a
criterion. You are talking about APERTURE diameter I think, and even
then, we use the f number which describes the ratio.

Click to expand...

When the F-stop of a lens is changed, the effective diameter of the lens is changed.

Gregory King said:

So you are talking about a 50mm f/2, a 100mm f/4, a 200mm f/8, and a
400mm f/16?

Click to expand...

Correct.

Gregory King said:

And focusing them all to the same distance would produce radically
different framing of your subject, so you'd tend to back up with the
longer lenses to get any kind of equivalence, and then the math
changes again.

Click to expand...

Or another way to put it, 50mm lens on a 35mm camera set for F2, 100mm on a 6x7 camera set for F4, 200mm on a 4x5 camera set for F8 and 400mm on an 8x10 camera set for F16. The DOF for all of the cameras will be identical and the framing will be more or less be the same.

Gregory King said:

So I find the "same DOF for the SAME F-STOP using the same SUBJECT
SIZE" to be a better rule-of-thumb. You gain DOF by backing up, but
lose it again by going to the larger absolute aperture diameter.

Click to expand...

This is true too. I also think photographers need to understand that sensor or film size has nothing to do with DOF. It's all controlled by the lens.

Jerry

One of the things I did to better understand DOF was to write an excel spread sheet that calculates and graphs CoC -vs- distance from the focus point. The inputs are FL, aperture, and focus distance, and the lines per mm desired in the final print (that last has nothing to do with calculating CoC, but I use it to calculate and display the maximum enlargement ratios depending on the CoC on the sensor). The chart also shows the diffraction blur (depends on aperture) and the hyperfocal distance (at a CoC of 0.030mm).

So one of the things that can be seen is that stopping down too much will result in diffraction blur greater than the CoC chosen for the desired DOF if the aperture is too small. The formula I used (and the lines per mm desired shows that the diffraction blur equals the DOF CoC for apertures smaller than f/13. While diffraction blur is something to be avoided since it affects the entire photo including the sharply focused subject, there is still some uncertainty in its use because it can be a large blur, but much dimmer than the subject and not as obvious as CoC blur. Since I can get sharp photos at f/16, I'm still trying to understand what conditions of lighting will make it strong enough to soften the image.

Using the spreadsheet I found it interesting to see how the rate of change of CoC behind the subject changes with the different parameters, even if the overall DOF remains almost the same. When trying to take an isolated shot (sharp subject with blurred background), the DOF can be misleading. The background might be behind the DOF but the CoC might still be small enough that it is not a smooth blur (not talking about lens related bokeh, but the difference between being able to see blurry features and a smooth blur.

I did post the spreadsheet in the files section of the Yahoo minolta group. I'm not sure if its still there after the various changes yahoo has made.

Tom