The DSLR Thread

[chaudhrysan]

CA and distortion in a lens is not just dependent on the size of the lens alone. A lot is also contributed by the lens design, arrangement and grouping of various elements and the glass composition. All other things being equal, if you scale down the design of a particular lens of a dSLR to the smaller sensor size of a P&S, both the lenses will exhibit similar CA and distortion characteristics. However, since you cannot fully follow the design principles of a dSLR lens in P&S due to design constraints of a compact form factor, a few compromises have to be made.

For Panasonic LX3, the Focal length at wide angle is 5.1
So when the lens is open at lets say F2.8 the Area is
pi*((5.1/(2*2.8))^2) = 2.61
When the Canon 24-70 is open at F2.8, the area is 57.7

The size of the aperture in case of the canon lens is more than 20 times compared to the LX3 at 2.8. Surely the amount of light entering (or rather exiting) should be more in case of the canon lens (larger pupil). But the exposure remains the same for the two. Do we mean that, all other things remaining same, the light density falling on the sensor is the same in both cases at same aperture and equivalent focal lengths??

[tsk1979]

Yes, what I mean to say is that if you take camera A, shoot a scene at 1/X shutter speed 1/Y aperture and Z ISO, and then do the same with a different camera with the same settings, you will get a similar histogram.

[kaushik_s]

Originally Posted by it_inspector

Point of weather sealing is not only for rain but for the fact DUST/MOISTURE etc. Its not uncommon to see people doing rally shots falling in pit of mud and body/lens combo getting a good wash in mud, no rain cover protects you there. This is one of the main reasons Pentax is still in market since almost all of upper pentax segment is Weather Sealed and those DA and Ltd`s just make me go drooling, but i can`t use any on my nikons

Personally i had beer spilled on my D3+70-200mm, i just washed it under tap and its all fine.

Righto, I didn't thought about those scenarios, but there will be hundred other scenarios where the lens or the camera will have to bear the burnt of the calamities. I think I'll keep off from Rally's

Originally Posted by Samurai

Well, Olympus does have some of the finest lenses. Checkout dpreview review of two of my lenses:

Olympus Zuiko Digital 50mm F2.0 Macro Lens Review: 4. Conclusion & samples: Digital Photography Review
Olympus Zuiko Digital ED 12-60mm 1:2.8-4.0 SWD Lens Review: 4. Conclusion & samples: Digital Photography Review

Samurai san, point of discussion was not the availability of the NEW ones but the availability of used cheap ones. I would bet that it won't be easy for you to find a used one and that's what you also expressed. I do know that Olympus make some good stuff.

Originally Posted by Samurai

My lenses weren't cheap, but I already own it. So, why change?

Don't change it, my post was just to pull your leg. Sorry.

Originally Posted by Samurai

Why compromise? I never worry of dust, water, humidity, moisture, fungus, etc. Never needed to clean the sensor either.

Money matters, can't spend too much money on buying all those high end stuffs. BTW, most of the time sensor gathers dust while changing lenses, and at that moment no weather sealing will help I guess.

[Samurai]

Originally Posted by kaushik_s

BTW, most of the time sensor gathers dust while changing lenses, and at that moment no weather sealing will help I guess.

That hasn't happened in Olympus dSLR system ever. It had working dust protection system since 2003, when the the first Olympus dSLR E1 came out.

[kaushik_s]

Originally Posted by Samurai

That hasn't happened in Olympus dSLR system ever. It had working dust protection system since 2003, when the the first Olympus dSLR E1 came out.

But SSWF is also a method of shaking off the dust from the sensor. So it's not preventing the dust to go inside the camera, right? In that sense many other Cameras have sensor cleaning system these days. If one is very careful while changing lenses than that itself is a good(probably the only) dust prevention mechanism.

[Proxima]

Guys I have a noob question:

Keeping the ISO constant, a large aperture (small F value) with a fast shutter speed and a small aperture with a slow shutter speed produces similar results. I know it has changes bokeh, depth of view.

But my question is how does one decide what to use? (Small F, fast shutter speed OR large F slow shutter speed)

[WanderNomad]

Originally Posted by livyodream

Nikon D90 costs close to 80K in BLR with 18-55 lens (which has live view).

Reality check buddy! Its around 67 - 68K with 18 - 135 and that too with proper bill and warranty.

[Samurai]

Originally Posted by navin

40D+17-55/2.8 IS (around $1600-1800)

Wrong, 40D is not fully weather sealed.

Originally Posted by http://www.dcresource.com/reviews/canon/eos_40d-review

One of the new features on the 40D (in terms of design) is that certain parts of the camera are now weather-sealed. These parts include the battery and memory card compartments, and the I/O ports. The various doors and covers on the optional battery grip and wireless file transmitter are sealed as well. This doesn't mean that you can take a shower with the 40D -- it's really just extra protection against dust and moisture.

The Olympus E3 + 12-60mm is fully weather sealed, what is the Canon or Nikon equivalent?

[it_inspector]

Originally Posted by kaushik_s

But SSWF is also a method of shaking off the dust from the sensor. So it's not preventing the dust to go inside the camera, right? In that sense many other Cameras have sensor cleaning system these days. If one is very careful while changing lenses than that itself is a good(probably the only) dust prevention mechanism.

Not true. Sigma SD14 comes with removable IR cut off filter. Whole point of this filter is to give user more options, if you want/need IR capable camera on a shoot immidietaly, with in less than a minute you have it and you can change it back when required. Compared to this no other DSLR has this feature. In order to get an IR capable camera you need to disassemble the whole camera to reach the sensor and then remove IR cut off filter and make necessary adjustments in the focusing system(namely just to adjust the sensor itself), in some DSLR`s even the mirror needs to be replaced. Some newer digital film cameras are also going this route too. The biggest advantage is that it stops dust from entering the sensor/mirror box while changing lenses.

And if the dust does manage to creep onto IR cut off filter, well then first of all its out of focus till f8 and secondly its way easier and less risky to clean compared to a sensor. Its a shame such good design and such a beautiful sensor in one of the worst cameras ever produced.

Nikon implemented a new dust removal-collection system in D60(i might be wrong about the model no. as its been a time and i don`t spend much time with base models). Its basically small tunnels inside the sensor box, particularily at the bottom of the mirror assembly. When the mirror slaps, it pushes air in a way that all the dust goes through these tunnels and gets stuck to adhesive piece of tape. This was meant to remove dust off the sensor and get it stuck to the tape. How effective it is/was i am not too sure. Maybe someone with a D60 can check it out.

Also Dust is not only the problem, moisture is worse than dust. Fungus is the biggest nightmare you can think of (ofcourse other than shutter death). And fungus on a sensor is not an easy task to repair.

[it_inspector]

What are the places around Chandigarh/Delhi where one can sell/buy secondhand Photography equipment for decent prices.

Thanks

[chaudhrysan]

But my question is how does one decide what to use? (Small F, fast shutter speed OR large F slow shutter speed)

A basic rule of thumb is that the minimum shutter speed should be equal or greater than 1/focal length of the lens you are using, for hand held photography.

Over this, you would use a higher shutter speed/ larger aperture combination if you want to catch motion photographs, or if you wish to keep the depth of field less. A lower shutter speed/ smaller aperture combination would be used if you want a larger depth of field.

[it_inspector]

Originally Posted by chaudhrysan

A basic rule of thumb is that the minimum shutter speed should be equal or greater than 1/focal length of the lens you are using, for hand held photography.

Over this, you would use a higher shutter speed/ larger aperture combination if you want to catch motion photographs, or if you wish to keep the depth of field less. A lower shutter speed/ smaller aperture combination would be used if you want a larger depth of field.

Actually that isn`t the best advice. What you use depends upon the situation and light. For example, if you are in snow and even if there are clouds, you will struggle to use f4 with anything below 1/2000, despite the lens range being 18-100mm, since there is huge amount of light.

I ran into a situation similar earlier this yr, for the required result I needed to have very slim DOF, so I was using f1.4 at 85mm but that meant some shots had blown highlights and pretty much everything was overexposed at 1/8000. Ended up using Nd400 filter with fill flash at 1/250 to rectify the situation.

Point here is, thumb size changes with each scenario

[tsk1979]

Wrong, no matter what condition whether its snow, pitch dark, raining. india losing cricket match or whatever, if your shutter speed is below 1/focal length, chances of camera shake increase in non stabilized hand held shots.

So if you are shooting at 25mm(35mm equiv), then you need a shutter speed of atleast 1/25 to get a non blurred shot.
Of course you are free to use a faster shutter speed, for example 1/2000, 1/4000 or whatever, but if you use 1/15, chances of a blurred shot increase.
If you are a surgeon and have exceptionally steady hands, then this may not apply to use. I know people who can shoot 1/100 with a 400mm lens, handheld, unstabilized, and still get sharp shots.

[Jaggu]

I never knew how the sensor cleaning works in Canon and found out that it has 3 things incorporated in auto sensor cleaning, pretty interesting:
Canon EOS 450D Digital SLR Camera - Canon UK

EOS Integrated Cleaning System
Canon’s built-in dust prevention system uses three methods to keep images blemish-free. (1) Specialised materials reduce dust generation within the camera. (2) A Self-Cleaning Sensor Unit shakes dust from the sensor each time the camera is turned on or off. (3) Stubborn dust spots are mapped for easy removal in Digital Photo Professional.

[it_inspector]

Originally Posted by tsk1979

Wrong, no matter what condition whether its snow, pitch dark, raining. india losing cricket match or whatever, if your shutter speed is below 1/focal length, chances of camera shake increase in non stabilized hand held shots.

So if you are shooting at 25mm(35mm equiv), then you need a shutter speed of atleast 1/25 to get a non blurred shot.
Of course you are free to use a faster shutter speed, for example 1/2000, 1/4000 or whatever, but if you use 1/15, chances of a blurred shot increase.
If you are a surgeon and have exceptionally steady hands, then this may not apply to use. I know people who can shoot 1/100 with a 400mm lens, handheld, unstabilized, and still get sharp shots.

Thank you, You just said it yourself it depends upon the person taking the shot.

In my particular case, i rarely take on assignments and when i do, i rarely get them out of studio or at day time, either way i end up using a tripod.

Btw, don`t mind but here`s a handheld 8sec shot inside a moving car with nikon 50mm @ f6.5 at 1:15am and i am definately not a surgeon. And i was definately not the driver, my friend was driving at that time at around 100kmph. If you do 100% zoom its looks like blur but its bad JPEG compression as the original RAW file is a little over 50mb while JPEG is around 28mb.