Messages

16

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 05:20:49 PM »

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.

So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.

Print a whole FF image at 1m wide, the noise hides quite well. Now take a crop of that same image and print that crop at 1m wide, do you think the noise will be no less apparent?

You'd need to shoot the cropped image at a lower ISO to show an equivalent amount of noise in the final print.

OK, now I know you're trolling. You failed to quote the part of my post that answers this:

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.

17

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 04:35:04 PM »

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.

So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.

ps - it seems like you're slowing coming around to understanding my argument. Using that metabones analogy, you got the bit about how both the combined effect of aperture and image circle is equal to the total amount of light coming through the system. You now seem to get the other end of the argument - FF allows you to work at higher ISO's than crop. If you could just accept this missing part of the puzzle about it being the larger size of the sensor which allows you to work at these higher ISO's, I think you'll have it. Or are you going to start arguing about some other random part of the rationale?

No, I'm content to stick with facts rather than come round to your argument.

18

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 02:41:15 PM »

What about using the FF system at a higher ISO? As the FF sensors larger area allows it to capture 2.56x more light, you can use an ISO 2.56x higher (just over a stop), without suffering from any more noise than the crop sensor.

You're trolling, surely.

ISO 10,000 on a typical APS-C sensor gives the same noise as ISO 25,600 on a typical FF. If you do choose to make use of the higher ISO's made available to you, the final exposure is the same, and the f1.8 crop system offers no low light advantage over an f2.8 full frame system.

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.

19

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 09:55:53 AM »

Think of the metabones speed booster. Imagine now that they created one which made a FF lens create an imaging circle to match the APS-C crop sensor found in a Canon camera - a 1.6x telecompressor. That way you could mount, say, a 24-70/2.8 on crop with the metabones adapter, and get an identical FoV that the lens achieves on FF.

The 24-70/2.8 would be turned into a 15-44/1.75, right?

Now, we all know f1.75 is faster than f2.8. No-one is disputing that. If you mount this lens on the crop sensor camera with the telecompressor, it will allow for more than a stop faster shutter speeds at equal ISO's. It is an f1.75 lens, and no-one can argue with that. But where does this metabones get this extra speed from? Its not magic - its just it compresses the larger image circle into a smaller one - that extra light from that larger FF image circle is now condensed down into a smaller, more intense imaging circle, and is then received by a smaller sensor. However, in total its only the same amount of light/photons coming in through the lens which hits the sensor. The FF sensor and the APS-C sensor with a telecompressor both receive an identical number of photons, but the APS-C sensor has brighter light presented to it - more light per area - in other words its just over a stop brighter.

I confess this the first time I've heard of a metabones speed booster but I get the idea and, yes, I'm with you so far.

ISO's are rated to make exposure calculations work. What one camera does to achieve ISO 1600 isn't the same as another camera at ISO 1600 - especially with different size formats. The larger sensor as a whole has more photons hitting it at a particular aperture, so it needs to amplify the resulting electrical signal less for any given ISO. And even some cameras with the same sensor have to do different amplification, such as the Sony NEX 7 and Sony SLT A77.

No, you've broken the sequence of logic from your metabones analogy. You can only say that the amount of light hitting the FF sensor is more because the FF sensor is bigger. The amount of light hitting each pixel is exactly the same, regardless of sensor size.

If you can't see that, haven't you ever wondered why FF sensors are typically just over a stop better than crop sensors when it comes to noise? This faster aperture of the Sigma simply allows the noisier sensor to work at lower ISO's to finally fight back. Use a 18-35/1.8 at 35mm f1.8 1/100th of a sec ISO 1000 on crop, or a 24-70/2.8 at 56mm f2.8 1/100th, ISO 1600 on FF and you'll find its the same framing, depth of field, exposure and noise. (well, it would be if the Sigma was slightly brighter at f1.75).

.

This is a compound error from the previous incorrect statement. Sensor size is not a factor in this.

20

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 04:39:37 AM »

I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

21

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 19, 2013, 05:06:04 PM »

There has been a lot of nonsense on this thread. It's pointless contributing now because the ones spreading the nonsense have entrenched themselves so deeply that they have no prospect of coming out of this with any dignity or credibility.

Let's not say these people have no dignity...that's personal and uncalled for.  They're simply sharing their opinion.

Yes, I shouldn't have put it that way. Apologies.

(Although, describing what f/1.8 means - whether on FF or APS-C - ought to be a matter of fact, not opinion).
 

22

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 19, 2013, 04:04:47 PM »

There has been a lot of nonsense on this thread. It's pointless contributing now because the ones spreading the nonsense have entrenched themselves so deeply that they have no prospect of coming out of this with any dignity or credibility.

23

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 18, 2013, 06:30:32 PM »

This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. 

You mean identical DOF. f1.8 will still give more light on APS-C than f/2.8 on full frame.

No. A FF sensor behind an f2.8 FF lens gathers 2.56x as much light as an f2.8 lens does on a 1.6x crop sensor due to the sensors 2.56x bigger surface area. If you only capture a fraction of all that FF f2.8 light by cropping it, well, the obvious happens from the light gathering point of view. The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating. In other words ISO 10,000 on crop is pretty much equal to ISO 25,600 on FF in terms of noise. So feel free to shoot smaller apertures on FF and use higher ISO's to get the same light gathering and noise.

The different amplification levels is a bit like how the Sony NEX 7 and the Sony SLT A77 both share an identical sensor, and give the same exposure with the same shutter speed, aperture and ISO, yet the SLT camera has a semi translucent mirror permanently in front of the sensor, acting like a neutral density filter you can't get rid of. Sony just cranked up the amplifier on the A77 a bit more to make it all seem good - at the expense of noise.

So f1.8 on a 1.6x crop is equivalent to f2.88 on FF in terms of both depth of field and light gathering.

Wuh? 

[citation needed]

24

Lenses / Re: Keep my 70-200 f/4 IS?

« on: April 14, 2013, 09:01:51 AM »

I intended to sell my f/4 IS after getting the f/2.8 IS II but found that I was still using the f/4 IS for travel, casual use, etc. I suppose it depends on whether the size and weight of the f/2.8 ever bothers you.

25

EOS Bodies - For Stills / Re: First big job using FF - for all the FF nay-sayers

« on: April 02, 2013, 08:11:40 PM »

-Rant- And there is no such thing as a FF nay-sayer. Some people think they prefer crop cameras over FF, but they just don't realize that their dinky toy sensors is utter crap in comparison to FF. I know this because I used to be one of them. .. Oh, those lost years.

I agree... I was one too lol.  I don't understand the "reach" arguement.  Your lens is what gives you reach.  A smaller sensor doesn't magnify what's in the frame, it crops.  Even if the cropped image is made up of more megapixels than the same frame cropped from a full frame image, wouldn't the full frame image still be better in terms of IQ, bokeh, etc ?(assuming all else is constant...)

The APS-C sensor is sampling the central part of the image with 1.6 times the pixel density of the FF sensor. If the glass is up to it and you are in the lower iso ranges you get better resolving power and equivalent noise out of APS-C (assuming same generation of sensors.... can't compare new to 4 year old...). Use poor glass and the FF outresolves... and at high ISO FF has less noise. Sampling the smaller area is problematic for wide angle shots but benificial to long shots... Lenses can be made smaller, cheaper, and lighter for APS-C, but at the cost of resolving power.... There is no easy answer, just a bunch of tradeoffs.

Clarification on the highlighted bits above:

APS-C pixel density relative to FF depends entirely on the number of pixels. A 7D has more than twice the pixel density of a 5D Mk III. A Nikon D800 (FF) has a higher pixel density than a Canon 40D (APS-C).

If an FF image is cropped to match an APS-C image (i.e. the same subject taken from the same distance with the same lens, focal length and aperture), the two images will have identical bokeh.

26

Lenses / Re: Samyang 24 TS confirmed for Photokina!

« on: April 01, 2013, 07:46:42 AM »

This from the website of the UK Samyang distributor. Can you spot the conflicting statements here?

27

Lighting / Re: Compact Manual Flash?

« on: March 29, 2013, 06:22:22 PM »

Just to confirm what others have suggested, an ST-E2 (Canon or Yongnuo) or a 90EX will give you full manual or E-TTL II control of your two 270 EX II flashes, complete with ratio control, FEC and 1st/2nd curtain sync, all through your 5D II's flash menu.

The 90EX can be set so that it doesn't contribute to the exposure when used as the on-camera master.

Adam, how do you assign groups to the 270EX II's? On all other Canon flashes you have to do that on the flash, even when you control them via the camera, there is no way, that I can see, that you could assign one 90EX to group A and another to group B. Further, no Canon flashes do remote second curtain sync. Once you go to remote triggering you can't select it, you can do HSS in remote, but not second curtain sync.

You're right - my bad. I didn't take into account the 270EX II's lack of group selection. It's a pity as it would make it much more useful.

28

Lighting / Re: Compact Manual Flash?

« on: March 29, 2013, 09:04:43 AM »

Just to confirm what others have suggested, an ST-E2 (Canon or Yongnuo) or a 90EX will give you full manual or E-TTL II control of your two 270 EX II flashes, complete with ratio control, FEC and 1st/2nd curtain sync, all through your 5D II's flash menu.

The 90EX can be set so that it doesn't contribute to the exposure when used as the on-camera master.

29

Lenses / Re: Why some lens says "macro"?

« on: March 22, 2013, 06:52:07 PM »

The 8-15mm fisheye zoom achieves 0.39x mag!

Wouldn't a fisheye lense be a MACKEREL lens?

  Pun-tastic!

30

EOS Bodies - For Stills / Re: Picture quality questions 6D.

« on: March 19, 2013, 07:37:44 PM »

I think we're at cross purposes here, neuro. I was talking about the Perfect Clear software referenced by the OP.